Underfloor material and floor structure

Abstract

To provide an underfloor material which has excellent waterproofing and workability and can be precut with a precut machine, and a floor structure provided with the same.SOLUTION: An underfloor material 20 includes an upper layer 21, an intermediate layer 22, and a lower layer 23, and is installed below a floor finishing material 10. The upper layer 21 and the lower layer 23 of the underfloor material 20 are made of medium-density fiberboard containing a water-repellent agent, and the intermediate layer 22 is made of a honeycomb panel in which a plurality of holes 22a extending in the thickness direction are formed in a honeycomb shape. Between the intermediate layer 22 and the upper layer 21 of the underfloor material 20, a non-breathable layer 24 is provided, which has a lower air permeability at the same pressure difference than the medium-density fiberboard.SELECTED DRAWING: Figure 3B

Description

[Technical field]

[0001] The present invention relates to a floor underlayment and a floor structure. [Background technology]

[0002] Conventionally, during the construction of buildings such as houses, floor underlayment materials would get wet during rain or snowfall, and floor underlayment materials made of plywood tend to absorb water easily, which could cause the four sides to expand in the thickness direction or lead to the growth of mold.

[0003] Therefore, after the installation of the underfloor material, a waterproof sheet is laid over the underfloor material to protect it, or a water-repellent coating is sprayed onto the surface of the underfloor material to apply a water-repellent treatment, thereby preventing the underfloor material from getting wet during rain or snow (for example, see Patent Document 1 below).

[0004] However, even if a waterproof sheet is laid on the underfloor material and cured, rainwater or melted snowwater may seep in between the waterproof sheet and the underfloor material through gaps in the waterproof sheet formed around vertical members such as pillars. The presence of the waterproof sheet makes it difficult for moisture to evaporate when it seeps in between the waterproof sheet and the underfloor material, resulting in the problem that the underfloor material absorbs the water. In addition, when applying a water-repellent coating by spraying the surface of the underfloor material with water-repellent paint, additional spraying work is required when applying the underfloor material, which increases the time and effort required for application of the underfloor material. In addition, there are areas where the water-repellent paint is not applied due to the formation of spots, and the adhesion rate of the water-repellent agent is poor, so there is a risk that the expected water-repellent effect will not be obtained.

[0005] Therefore, in Japanese Patent Application No. 2022-170094, the applicant of the present application has proposed a floor underlayment in which at least the upper layer of the floor underlayment is made of a medium-density fiberboard with low water absorption, and further, the medium-density fiberboard is impregnated with a water repellent agent so that the contact angle of water with respect to the surface is greater than 90 degrees. When such a floor underlayment is used, even if rainwater or melted snow water penetrates into the gap between the waterproof sheet and the floor underlayment through the gap in the waterproof sheet formed around the vertical material such as a pillar before the construction of the floor finishing material, the rainwater or melted snow water becomes water droplets with a contact angle greater than 90 degrees and remains in the above-mentioned gap, and the water droplets act as a plug, so that the rainwater or melted snow water can be prevented from penetrating between the waterproof sheet and the floor underlayment one after another. In other words, by using the above-mentioned floor underlayment, it is possible to prevent the floor underlayment of the building under construction from getting wet during rainy weather or snowfall.

[0006] By the way, while medium density fiberboard has low water absorption and excellent waterproofing properties, it is heavy. Therefore, when using a thick underfloor material, if the entire underfloor material is made of medium density fiberboard, the weight will be heavy and workability will be poor.

[0007] Therefore, in the above-mentioned application (Patent Application No. 2022-170094), the applicant proposes to reduce the weight of the floor underlayment by making the floor underlayment a three-layer structure, with the upper and lower layers being composed of medium-density fiberboard containing a water-repellent agent, while the middle layer is composed of a relatively lightweight, highly rigid honeycomb panel with multiple holes extending in the thickness direction. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Patent No. 5592033 Summary of the Invention [Problem to be solved by the invention]

[0009] By the way, in the case of thick underfloor materials, they are often pre-cut rather than cut at the construction site. A pre-cutting machine is equipped with a suction conveying device as described in JP 2013-129037 A, for example, and in the pre-cutting machine, the composite board for the underfloor material (before pre-cutting) is conveyed while being sucked up by the suction pad of the suction conveying device.

[0010] However, the above-mentioned three-layered underfloor material uses a medium-density fiberboard with excellent breathability for the upper and lower layers, and a honeycomb panel with multiple holes formed in the thickness direction for the middle layer, so that air can easily pass through in the thickness direction. Therefore, when the underfloor material has the above-mentioned three-layered structure, there is a problem that the composite board for the underfloor cannot be sucked up by the suction pad, and the pre-cut machine cannot be used. Specifically, when a pile of multiple composite boards for the underfloor is transported one by one to the cutting device of the pre-cut machine using a suction conveying device, the suction pad of the suction conveying device sucks up multiple boards at the same time, so that the boards cannot be transported one by one to the cutting device and cannot be cut.

[0011] The present invention has been made in consideration of the above-mentioned points, and its object is to provide a floor underlayment material that has excellent waterproofing and workability and can be pre-cut using a pre-cutting machine, and a floor structure equipped with the same. [Means for solving the problem]

[0012] In order to achieve the above object, the present invention provides an underfloor material in which the upper and lower layers are constructed of medium-density fiberboard containing a water-repellent agent, and the middle layer is constructed of a honeycomb panel, and a non-breathable layer, which has a lower air permeability than the medium-density fiberboard at the same pressure difference, is provided between at least one of the two medium-density fiberboards (upper and lower layers) and the honeycomb panel (middle layer).

[0013] Specifically, the first invention is a floor underlayment material comprising an upper layer, a middle layer and a lower layer, which is applied below a floor finishing material, wherein the upper and lower layers are composed of a medium-density fiberboard containing a water repellent agent, the middle layer is composed of a honeycomb panel having a plurality of holes extending in the thickness direction formed in a honeycomb shape, and a non-breathable layer having an air permeability lower than that of the medium-density fiberboard at the same pressure difference is provided at least either between the middle layer and the upper layer or between the middle layer and the lower layer.

[0014] In the first invention, the upper layer of the underfloor material is made of medium density fiberboard (MDF) with low water absorption. Medium density fiberboard is a wood board formed by hot pressing wood fibers together with an adhesive to form a board, and has a low water absorption rate. Therefore, even if rainwater or melted snow water penetrates between the waterproof sheet and the underfloor material during construction of a building such as a house (before the application of the floor finishing material), it is not absorbed into the underfloor material. In addition, with such underfloor material, even in the places where nails are driven in, the wood fibers coated with adhesive are in close contact with the nails that are driven in so as to push aside the wood fibers, making it difficult for rainwater or melted snow water to penetrate into the nail holes. By using such underfloor material with excellent waterproofing and nail hole water stopping properties, even if rainwater or melted snow water penetrates between the waterproof sheet and the underfloor material before the application of the floor finishing material, the underfloor material will not absorb water and deform (expand in thickness, warp, twist), and mold growth can also be suppressed.

[0015] In the first invention, the upper layer of the underfloor material is made of a medium-density fiberboard containing a water-repellent agent (having water repellency). Therefore, even if rainwater or melted snow water penetrates into the gap between the waterproof sheet and the underfloor material through the gap in the waterproof sheet formed around vertical members such as pillars before the construction of the floor finishing material, the rainwater or melted snow water becomes water droplets with a contact angle of more than 90 degrees on the upper surface of the underfloor material, does not wet and spread on the upper surface of the underfloor material, and remains in the above-mentioned gap in the form of water droplets. The water droplets remaining in the gap act as a plug, making it difficult for the rainwater or melted snow water to penetrate further into the gap. In other words, by making the upper layer of the underfloor material a water-repellent layer having water repellency, it is possible to suppress the rainwater or melted snow water from penetrating between the waterproof sheet and the underfloor material one after another. Even if water droplets reach the joints of the underfloor material, those with a contact angle of more than 90 degrees with the top surface of the underfloor material act as plugs, preventing rainwater and melted snow from penetrating the joints. In other words, the top layer of the underfloor material becomes a water-repellent layer, which has water-repellent properties, and can also prevent rainwater and melted snow from penetrating through the joints of the underfloor material.

[0016] In addition, in the first invention, by simply using a floor underlayment whose upper layer is made of water-repellent medium-density fiberboard, it is possible to easily install a floor underlayment with excellent waterproofing that makes it difficult for rainwater or melted snow water to penetrate between the waterproof sheet and the floor underlayment before the installation of the floor finishing material, and which does not absorb the water even if it does penetrate, without having to perform special processing work such as spraying water-repellent paint after installation of the floor underlayment, as has been done in the past.

[0017] Furthermore, in the first invention, the underfloor material has a multi-layer structure having an upper layer, a middle layer, and a lower layer, and the upper and lower layers are made of medium density fiberboard that has excellent water repellency and excellent waterproofing and nail hole water stopping properties, while the middle layer is made of a honeycomb panel that has a plurality of holes and is relatively lightweight and has high rigidity, thereby reducing the weight of the underfloor material. By configuring it in this way, it is possible to provide a highly waterproof underfloor material that does not absorb rainwater or melted snow water even if it penetrates between the waterproof sheet and the underfloor material before the construction of the floor finishing material, without compromising workability.

[0018] In addition, in the first invention, a non-breathable layer having a lower air permeability than the medium-density fiberboard at the same pressure difference is provided between at least one of the two medium-density fiberboards (upper and lower layers) and the honeycomb panel (middle layer). With this configuration, air is less likely to pass through the underfloor material in the thickness direction compared to when no non-breathable layer is provided. Therefore, with the above configuration, the composite board for the underfloor material can be sucked up (transported) one by one by the suction pad of the suction transport device attached to the precutting machine, and can be precut by the precutting machine. Therefore, according to the first invention, it is possible to provide an underfloor material that has excellent waterproofing and workability and can be precut by the precutting machine.

[0019] Furthermore, conventional underfloor materials using plywood (especially thick plywood with a thickness of 24 mm or more) tend to gradually lose weight over time, causing gaps to form between the underfloor material and the nails used for installation, which can lead to squeaking (noises), but in the first invention, the upper and lower layers of the underfloor material are made of medium-density fiberboard, which is less susceptible to deterioration over time. Therefore, there is no gap between the underfloor material and the nails used for installation, which can cause squeaking.

[0020] As mentioned above, by constructing the intermediate layer with a honeycomb panel, it is possible to reduce the weight, but the horizontal rigidity is lower than that of conventional floor underlayment made of plywood. Therefore, if a floor underlayment with a honeycomb panel intermediate layer is used, the in-plane shear strength of the horizontal structural member cannot be expressed, and it may be difficult to obtain the so-called existing floor ratio that is recognized for thick plywood.

[0021] However, according to the first invention, not only the upper layer that contributes to waterproofing but also the lower layer are made of medium density fiberboard. Medium density fiberboard has high rigidity like plywood and is also used as a load-bearing surface material for walls, etc. Therefore, by constructing the upper and lower layers with medium density fiberboard, it is possible to increase the values ​​of the "short-term standard shear strength" and "existing floor ratio" of the horizontal structural members, which are required to be within a specified range when performing structural calculations, even if the middle layer is made of honeycomb panels.

[0022] A second invention is characterized in that in the first invention, the upper layer and the lower layer are thinner than the intermediate layer, and the air-impermeable layer is thinner than the upper layer and the lower layer.

[0023] In the second aspect of the present invention, the underfloor material is configured such that the intermediate layer, which is made of a honeycomb panel that is lighter than a medium-density fiberboard, is thicker than the upper and lower layers, which are made of medium-density fiberboard. The non-breathable layer is thinner than the upper and lower layers, which are thinner than the intermediate layer. This configuration allows the underfloor material to be made even lighter.

[0024] A third invention is the first or second invention, characterized in that the air-impermeable layer is made of paper, a resin sheet or a nonwoven fabric.

[0025] In the third invention, the non-breathable layer is made of paper, a resin sheet, or a nonwoven fabric. The air permeability of paper, a resin sheet, and a nonwoven fabric can be easily adjusted by appropriately changing the density, material, the presence or absence of coating, etc. Therefore, according to the third invention, it is easy to configure a non-breathable layer whose air permeability at the same pressure difference is lower than that of a medium density fiberboard.

[0026] A fourth invention is the third invention, characterized in that the intermediate layer is made of a paper honeycomb panel, the non-breathable layer is made of paper, and the non-breathable layer is adhered to the intermediate layer.

[0027] In the fourth invention, the intermediate layer is made of a paper honeycomb panel, and the non-breathable layer is made of paper. By making the intermediate layer and the non-breathable layer out of the same material (paper) in this way, the intermediate layer and the non-breathable layer can be easily bonded together using an adhesive suitable for bonding paper.

[0028] The fifth invention is a floor structure comprising an underfloor material and a floor finishing material applied on the underfloor material, characterized in that the underfloor material is the underfloor material of the first invention.

[0029] In the fifth invention, the above-mentioned waterproof underfloor material is used in a floor structure that includes an underfloor material and a floor finishing material. Therefore, even if rainwater or melted snow water penetrates between the waterproof sheet and the underfloor material before the floor finishing material is installed, the underfloor material will not absorb water and deform (expand in thickness, warp, twist), and mold growth can be suppressed. In addition, unlike conventional floor structures, the waterproof underfloor material can be easily installed without special processing such as spraying water-repellent paint after the installation of the underfloor material. Effect of the Invention

[0030] As explained above, according to the present invention, in an underfloor material in which the upper and lower layers are made of medium-density fiberboards containing a water repellent and the middle layer is made of a honeycomb panel, by providing a non-breathable layer having a lower air permeability than the medium-density fiberboards at the same pressure difference between at least one of the two medium-density fiberboards (upper and lower layers) and the honeycomb panel (middle layer), an underfloor material with excellent waterproofing and workability can be easily manufactured. Furthermore, according to another invention, a floor structure with excellent waterproofing and workability including the above underfloor material can be provided. [Brief description of the drawings]

[0031] [Figure 1] FIG. 1 is a perspective view showing a part of a floor structure according to the first embodiment, with a cutaway portion. [Diagram 2] FIG. 2 is a cross-sectional view showing the floor structure according to the first embodiment. [Figure 3A] FIG. 3A is an exploded perspective view of the underfloor material. [Figure 3B] FIG. 3B is a perspective view showing a part of the underfloor material cut away. [Figure 4A] FIG. 4A is a cross-sectional view showing the state near a pillar of a conventional floor structure before a floor finishing material is applied. [Figure 4B] FIG. 4B is a cross-sectional view showing the state near the pillar of the floor structure according to the first embodiment before the application of a floor finishing material. [Figure 5A]FIG. 5A is a cross-sectional view showing the state near a joint of an underfloor material in a conventional floor structure before a floor finishing material is applied. [Figure 5B] FIG. 5B is a cross-sectional view showing the state near the joints of the under-floor material of the floor structure according to the first embodiment before the application of the floor finishing material. [Figure 6] FIG. 6 is a schematic diagram showing the permeability test. [Figure 7] Figure 7 shows the results of the permeability test. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] Hereinafter, the embodiments of the present invention will be described in detail with reference to the drawings. The following embodiments are essentially preferred examples, and are not intended to limit the scope of the present invention, its applications, or its uses.

[0033] First Embodiment of the Invention As shown in Figures 1 and 2, the floor structure 1 is formed by laying a plurality of plate-shaped floor finishing materials 10, ..., 10 on a plurality of plate-shaped floor underlayment materials 20, ..., 20. Note that in this embodiment 1, an example will be described in which the floor structure 1 is applied to a floor assembly using a joist-less construction method in which the floor underlayment materials 20 are fixed to joists or floor beams without providing joists.

[0034] -Floor structure configuration- As shown in Figures 1 and 2, the floor structure 1 comprises a floor finishing material 10 and a floor underlayment material 20. The multiple floor underlayment materials 20,...,20 are laid on multiple joists (floor beams on the second floor) 2,...,2 arranged at intervals in the floor structure of a building, and multiple floor finishing materials 10,...,10 are laid on top of them. In the floor structure 1 shown in Figure 1, multiple connecting materials 3 are provided perpendicular to each pair of joists 2,2 so as to connect each pair of adjacent joists 2,2.

[0035] When the floor structure 1 is provided on the first floor of a building (is part of the first floor floor assembly), the reference numeral 2 in Fig. 1 and Fig. 2 indicates a joist, and the multiple floor underlayment materials 20, ..., 20 are laid on the multiple joists 2, ..., 2. On the other hand, when the floor structure 1 is provided on the second floor of a building (is part of the second floor floor assembly), the reference numeral 2 indicates a floor beam, and the multiple floor underlayment materials 20, ..., 20 are laid on the multiple floor beams 2, ..., 2.

[0036] The floor finishing material 10 may have any configuration, but may be, for example, a wooden base material with a decorative material such as a decorative sheet or veneer adhered to the upper surface thereof by an adhesive.

[0037] <Detailed composition of floor underlayment> As shown in Figures 3A and 3B, the floor underlayment material 20 comprises an upper layer 21, an intermediate layer 22, a lower layer 23, and an air-impermeable layer 24. The upper layer 21, the intermediate layer 22, and the lower layer 23 are laminated in this order from top to bottom. In this embodiment 1, the air-impermeable layer 24 is provided between the upper layer 21 and the intermediate layer 22. Note that, since this embodiment 1 is applied to a floor assembly using a joist-less construction method, the floor underlayment material 20 is formed thicker (20 mm or more thick) than when applied to a floor assembly using a joist construction method in which joists are provided.

[0038] The upper layer 21 and the lower layer 23 have a density (g / cm 3 ) is 0.6 or more and less than 0.85. In this embodiment, the board is made of a medium density fiberboard (MDF) having a density of 0.7 g / cm 3 A medium density fiberboard having a thickness of 2 to 9 mm is used for the upper layer 21 and the lower layer 23. From the viewpoint of suppressing warping, it is preferable that the upper layer 21 and the lower layer 23 have the same thickness, but the upper layer 21 and the lower layer 23 may have different thicknesses.

[0039] The medium density fiberboard constituting the upper layer 21 and the lower layer 23 contains an adhesive having excellent water resistance. In the present embodiment 1, the upper layer 21 and the lower layer 23 are made of a medium density fiberboard containing a urea-melamine co-condensation resin adhesive. The adhesive used for the medium density fiberboard is not limited to the urea-melamine co-condensation resin adhesive, and may contain diphenylmethane diisocyanate, phenol resin, or the like.

[0040] The intermediate layer 22 is composed of a honeycomb panel in which a plurality of holes 22a extending in the thickness direction are formed in a honeycomb shape. The honeycomb panel constituting the intermediate layer 22 is formed by bonding together, with a water-resistant adhesive, paper that has been made water-resistant by applying a water-resistant agent. Note that the method of making the paper water-resistant is not limited to applying a water-resistant agent, and a resin may be applied instead of the water-resistant agent, or the paper may be impregnated with the water-resistant agent or resin.

[0041] 3B, in the present embodiment 1, a honeycomb panel with no surface material attached to the outer periphery and with the outermost peripheral holes 22a exposed is used as the intermediate layer 22. If the paper constituting the intermediate layer 22 (honeycomb panel) is not water resistant or has low water resistance, it is preferable to apply or impregnate the outer periphery of the intermediate layer 22 (honeycomb panel) with a water resistant agent or resin.

[0042] The honeycomb panel constituting the intermediate layer 22 may have a surface material attached to its outer periphery. The surface material attached to the outer periphery of the intermediate layer 22 is preferably made of a water-resistant material, or is made water-resistant by applying or impregnating a water-resistant agent or resin thereto.

[0043] In the first embodiment, a honeycomb panel made of paper is used as the intermediate layer 22, but the material of the honeycomb panel constituting the intermediate layer 22 may be any material as long as the density of the intermediate layer 22 is smaller than the density of the upper layer 21 and the lower layer 23, preferably equal to or less than half the density of the upper layer 21 and the lower layer 23, and more preferably equal to or less than one tenth the density of the upper layer 21 and the lower layer 23. In the present embodiment, the density is 0.05 g / cm 3 A honeycomb panel having a thickness of 10 to 20 mm is used as the intermediate layer 22.

[0044] The non-breathable layer 24 is configured so that the air permeability at the same pressure difference is lower than the air permeability of the medium density fiberboard that constitutes the upper layer 21 and the lower layer 23. Specifically, in the present embodiment 1, the non-breathable layer 24 is configured so that the air permeability at the same pressure difference is lower than the air permeability of the medium density fiberboard that constitutes the upper layer 21 and the lower layer 23. 2 More than 1000g / m 2 The following are made of paper with a thickness of 0.02 mm to 1.0 mm.

[0045] The non-breathable layer 24, like the intermediate layer 22, is made of paper that has been made water-resistant by applying a water-resistant agent, and is attached to the upper surface of the intermediate layer 22 with a water-resistant adhesive. The method of making the paper water-resistant is not limited to applying a water-resistant agent, and a resin may be applied instead of the water-resistant agent, or the paper may be impregnated with a water-resistant agent or a resin. In the first embodiment, the non-breathable layer 24 is made of paper, which is the same material as the intermediate layer 22, and therefore the non-breathable layer 24 can be easily attached to the upper surface of the intermediate layer 22 by using an adhesive suitable for adhering paper.

[0046] The non-breathable layer 24 does not have to be made of paper as long as it is configured so that the air permeability at the same pressure difference is lower than that of a medium density fiberboard. The non-breathable layer 24 may be made of a resin sheet (vinyl chloride, olefin, polyester, etc.) or a nonwoven fabric, either alone or in layers. The non-breathable layer 24 may also be a layer that does not allow air to pass through at all.

[0047] The underfloor material 20 is a sandwich panel in which an intermediate layer 22 made of a honeycomb panel with a non-breathable layer 24 made of paper attached to the upper surface is sandwiched between an upper layer 21 and a lower layer 23 made of medium-density fiberboard, and the layers are bonded together with a water-resistant adhesive. In this way, by making the underfloor material 20 into a multi-layer structure including the intermediate layer 22 and configuring the intermediate layer 22 from a honeycomb panel that has a significantly lower density and is lighter than medium-density fiberboard, the weight of the underfloor material 20 can be reduced.

[0048] Specifically, in the case of an underfloor material 20 that is 910 mm x 1820 mm and 24 mm thick, a single-layer structure (medium-density fiberboard only) would weigh 27.8 kg, but if it is a multi-layer structure with an intermediate layer 22 made of a 13 mm-thick honeycomb panel sandwiched between upper and lower layers 21 and 23 made of 5.5 mm-thick medium-density fiberboard, the weight will be 15.6 kg. This shows that by making the underfloor material 20 of a multi-layer structure rather than a single-layer structure, it is possible to reduce weight.

[0049] In the above-mentioned underfloor material 20, a plurality of holes 22a are formed in the honeycomb panel constituting the intermediate layer 22, but the upper and lower ends of the plurality of holes 22a in the honeycomb panel are blocked by the non-breathable layer 24 and the upper and lower layers 21 and 23. Therefore, even if water seeps into the end grain of the underfloor material 20, if the outer periphery of the intermediate layer 22 is not covered with a sheet or thin plate, the water will only come into contact with the wall surfaces defining the outermost holes 22a of the underfloor material 20, and will not come into contact at all with the wall surfaces defining the internal holes 22a.

[0050] (non-breathable) As described above, the underfloor material 20 is made of an upper layer 21 and a lower layer 23 of medium-density fiberboard so that the water absorption rate is low from the viewpoint of waterproofing. Medium-density fiberboard has a significantly lower airflow resistance than plywood, which has been used as a conventional underfloor material. In addition, the intermediate layer 22, which is made of a honeycomb panel in which a plurality of holes 22a extending in the thickness direction are formed in a honeycomb shape, has a significantly lower airflow resistance in the thickness direction than the upper layer 21 and the lower layer 23 made of a plate-like body. Therefore, the underfloor material 20, in which the upper layer 21 and the lower layer 23 are made of medium-density fiberboard and the intermediate layer 22 is made of a honeycomb panel, has a significantly lower airflow resistance in the thickness direction than a conventional underfloor material made of plywood.

[0051] Furthermore, air permeability tests were conducted on medium density fiberboard and plywood.Specifically, test specimen A was made of medium density fiberboard with dimensions of 560mm x 560mm x 9.2mm, and test specimen B was made of plywood with dimensions of 560mm x 560mm x 12mm. Test specimens A and B were placed above an airtight box with an opening on the top and an opening dimension (air permeability dimension) of 500mm x 500mm, so as to block the opening.The pressure difference before and after test specimens A and B was gradually changed by pressurizing and depressurizing the airtight box using a pressure pump, and the air permeability at each pressure difference was measured using a microflowmeter.

[0052] The relationship between the pressure difference and the airflow rate was regressed using the following formula (Formula 1). As a result, the following formula (Formula 2) was obtained for specimen A (MDF), and the following formula (Formula 3) was obtained for specimen B (PW). Note that Q is the airflow area per square meter at 20°C and an air density of 1 atm. 2 Airflow per m 3 / (h m 2 )], ΔP is the pressure difference [Pa], and n is the gap characteristic value (usually 1 to 2).

number

number

number

[0053] The above formulas (2) and (3) are, when ΔP=1[Pa], Q MDF =0.00514, Q PW =0.000595, so Q MDF / Q PW From this result, it is found that test specimen A made of medium density fiberboard is 8.6 times more breathable (has significantly lower airflow resistance) than test specimen B made of plywood.

[0054] In addition, from the following formulas (4) and (5) and the above formulas (2) and (3), formulas (6) and (7) were obtained to calculate the effective opening area (αA) of test specimens A and B. Note that α is the flow coefficient and A is the cross-sectional area [cm 2 ], V is the equivalent wind speed [m / s], and A' is the ventilation area (0.25m 2 ), and ρ is the density of air (1.205 [kg / m 3 ]).

number

number

number

number

[0055] The above formulas (6) and (7) are, when ΔP = 1 [Pa], αA MDF =0.0111[cm 2 / m 2 ], and αA PW =0.00128[cm 2 / m 2 In other words, the effective opening area (αA) is 1 m for test piece A made of medium density fiberboard. 2 This corresponds to an opening of 1 mm square per square meter, and for specimen B made of plywood, 2This corresponds to an opening of 0.36 mm square per square inch. This difference in effective opening area also shows that test specimen A, made of medium density fiberboard, is significantly more breathable (has significantly lower airflow resistance) than test specimen B, made of plywood.

[0056] From the above results, it can be seen that the floor underlayment 20, in which the upper layer 21 and lower layer 23 are constructed of medium-density fiberboard and the middle layer 22 is constructed of a honeycomb panel, is significantly more breathable (has significantly lower air resistance) than floor underlayment made of conventional plywood.

[0057] In contrast, in the underfloor material 20 of the present embodiment 1, an impermeable layer 24 having a higher airflow resistance than that of the medium-density fiberboard is provided between at least one (upper layer 21) of the two medium-density fiberboards (upper layer 21 and lower layer 23) and the honeycomb panel (middle layer 22). With this configuration, one end (upper end in the present embodiment 1) of the holes 22a of the honeycomb panel constituting the middle layer 22 is blocked by the impermeable layer 24, so that the airflow resistance in the thickness direction of the underfloor material 20 increases compared to the case where the impermeable layer 24 is not provided, and the underfloor material 20 is difficult for air to pass through in the thickness direction (the amount of airflow at the same pressure difference is low). Therefore, the composite boards for constituting the underfloor material 20 can be sucked up (transported) one by one by the suction pad of the suction transport device attached to the precutting machine, and can be precut by the precutting machine.

[0058] (water repellency) The underfloor material 20 is configured so that the contact angle of water with the upper surface 20a is greater than 90 degrees. Specifically, in this embodiment 1, when forming the medium-density fiberboard that constitutes the upper layer 21 of the underfloor material 20, paraffin (water repellent) is added in an amount necessary for the surface of the medium-density fiberboard to be water-repellent (the contact angle of water at any point on the surface is greater than 90 degrees), thereby configuring the upper surface 20a to be water-repellent.

[0059] From the viewpoint of excellent water repellency, the upper surface 20a of the underfloor material 20 is preferably configured so that the contact angle with water is 110 degrees or more, and more preferably so that the contact angle with water is 120 degrees or more.

[0060] In the first embodiment, the lower layer 23 is also configured in the same manner as the upper layer 21. That is, the underfloor material 20 is configured so that the contact angle of water with the lower surface 20b is also greater than 90 degrees.

[0061] (Water absorption rate) The upper layer 21 and the lower layer 23 of the underfloor material 20 are configured to have a water absorption rate of 15% or less. The upper layer 21 and the lower layer 23 are preferably configured to have a water absorption rate of 13.6% or less, and more preferably to have a water absorption rate of 13.2% or less.

[0062] Here, the water absorption rate is determined by measuring the weight (m1) of a 50 mm square test specimen that has reached a constant weight in an environment of relative humidity 65±5%, placing the test specimen in water at 20±1°C, and then immersing the specimen for 24 hours, and then removing the specimen and measuring its weight (m2) in a water absorption test. The water absorption rate is calculated from the weight difference of the test specimen before and after immersion in water measured in the water absorption test (the value obtained by dividing the weight difference of the test specimen before and after immersion (m2-m1) by the weight m1 before immersion and multiplying this value by 100).

[0063] As described above, in a medium-density fiberboard containing an adhesive with excellent water resistance, the wood fibers are coated with the adhesive, which makes it difficult for water to penetrate between the wood fibers, resulting in a low water absorption rate. Therefore, by using an adhesive with excellent water resistance and a water repellent agent in the molding of the medium-density fiberboard that constitutes the upper layer 21 and the lower layer 23 and adjusting the blending ratio, the water absorption rate of the upper layer 21 and the lower layer 23 can be set to a desired water absorption rate, which in this embodiment is 15% or less (preferably 13.6% or less, more preferably 13.2% or less).

[0064] The water absorption test was carried out on 12 mm thick structural plywood (cedar) and structural plywood (surface layer larch, core layer cedar) that were conventionally used as floor underlayment, and the water absorption was calculated to be 82% and 61%. This shows that the water absorption of the upper layer 21 and lower layer 23 of the floor underlayment 20 of the present embodiment 1 is significantly lower than that of conventional floor underlayment.

[0065] (Moisture permeability) The upper layer 21 and the lower layer 23 of the underfloor material 20 are made of medium-density fiberboard, and therefore have a lower moisture permeability resistance than plywood or the like of the same thickness. Specifically, the upper layer 21 and the lower layer 23 are each configured to have a moisture permeability specific resistance of less than 0.13 m·s·Pa / ng. In addition, in the present embodiment 1, the underfloor material 20 is not made of only medium-density fiberboard, but is configured as a sandwich panel in which an intermediate layer 22 made of a honeycomb panel is sandwiched between the upper layer 21 and the lower layer 23 made of medium-density fiberboard. In the first place, medium-density fiberboard has a lower moisture permeability resistance than plywood or the like, but as described above, by making the underfloor material 20 into a multi-layer structure in which a honeycomb panel is sandwiched between two sheets of medium-density fiberboard, the thickness of the medium-density fiberboard can be made thinner than when the underfloor material 20 has a single-layer structure made of only medium-density fiberboard, and further, since the moisture permeability resistance of the honeycomb panel in which a plurality of holes 22a are formed can be regarded as almost zero, the moisture permeability resistance of the underfloor material 20 can be kept low.

[0066] In this embodiment 1, a non-breathable layer 24 is provided between the middle layer 22 and the upper layer 21. However, since the non-breathable layer 24 is made of paper that does not have a very high moisture permeability resistance, the presence of the non-breathable layer 24 does not significantly increase the moisture permeability resistance of the floor underlayment material 20.

[0067] -Manufacturing method for floor underlayment- A medium density fiberboard that constitutes the upper layer 21 and the lower layer 23, and a paper honeycomb panel that constitutes the middle layer 22 are fabricated, and paper is prepared that constitutes the breathable layer 24. The breathable layer 24 made of prepared paper is attached to the top surface of the middle layer 22 that is the formed honeycomb panel with a water-resistant adhesive.

[0068] The upper layer 21, the middle layer 22 to which the non-breathable layer 24 is attached, and the lower layer 23 are layered from top to bottom and bonded together with a water-resistant adhesive to form a composite board. The formed composite board is sucked up by a suction pad of a suction conveying device attached to a pre-cutting machine (not shown), conveyed to a cutting device in the pre-cutting machine, and cut to a specified size, thereby producing the floor underlayment material 20.

[0069] In the present embodiment 1, a non-breathable layer 24 made of paper having a lower air permeability at the same pressure difference than the medium-density fiberboard constituting the upper layer 21 is provided between the upper layer 21 and the intermediate layer 22, and one end (the upper end in the present embodiment 1) of the holes 22a of the honeycomb panel constituting the intermediate layer 22 is blocked by the non-breathable layer 24. The underfloor material 20 of the present embodiment 1 configured in this manner is less likely to allow air to pass in the thickness direction than a conventional underfloor material without the non-breathable layer 24 (one end of the holes 22a of the honeycomb panel is not blocked by the non-breathable layer). Therefore, even if the underfloor material 20 has a multi-layer structure including the medium-density fiberboard and the honeycomb panel, the composite board for the underfloor material 20 can be sucked up (transported) one by one by the suction pad of the suction transport device attached to the precutting machine, and can be precut by the precutting machine.

[0070] -Floor structure construction method- The floor structure 1 is constructed as follows.

[0071] First, a floor underlayment 20 is installed above a plurality of joists 2, ..., 2 that are arranged at intervals in the floor structure of a building. Specifically, a plurality of floor underlayment materials 20, ..., 20 are laid on the plurality of joists 2, ..., 2, and each floor underlayment material 20 is fixed with nails 5 to the joists 2 and connecting materials 3 that each floor underlayment material 20 straddles.

[0072] After the underfloor material 20 is installed, a plurality of floor finishing materials 10, ..., 10 are installed on the installed plurality of floor underlay materials 20, ..., 20. Specifically, a plurality of floor finishing materials 10, ..., 10 are laid on the plurality of floor underlay materials 20, ..., 20, and each floor finishing material 10 is fixed to the underfloor material 20 on which the floor finishing material 10 is placed with adhesive and staples.

[0073] The floor structure 1 is constructed in the manner described above.

[0074] -Floor structure characteristics- <Waterproofing of floor underlayment> 4A, the conventional underfloor material 120 made of plywood that has not been treated with water repellent has a high water absorption rate. Therefore, before the floor finishing material is applied, if rainwater or melted snow water infiltrates into the gap S101 between the underfloor material 120 and the waterproof sheet 125 that is lifted by the vertical members such as pillars of the waterproof sheet 125 for curing, the underfloor material 120 becomes wet with the rainwater or melted snow water (absorbs the water).

[0075] Specifically, in a conventional underfloor material 120 in which the upper surface 120a is highly wettable due to lack of a water-repellent treatment, rainwater or melted snow water that seeps into the gap S101 between the waterproof sheet 125 and the underfloor material 120 through gaps in the waterproof sheet 125 is absorbed into the surface layer veneer at the point where it seeps in and flows in the fiber direction of the surface layer veneer. As the rainwater or melted snow water absorbed into the surface layer veneer flows in the fiber direction in this way, the rainwater or melted snow water spreads over the entire surface layer veneer and is absorbed into the surface layer veneer one after another.

[0076] In contrast, in this embodiment 1, the upper layer 21 of the underfloor material 20 is made of medium-density fiberboard, which has low water absorption, and the medium-density fiberboard is further configured to contain a water-repellent agent so that the contact angle of water with the surface is greater than 90 degrees (water-repellent).

[0077] Therefore, as shown in Fig. 4B, even if rainwater or melted snow water infiltrates into the gap S1 between the waterproof sheet 25, which is raised by the vertical members such as pillars of the curing waterproof sheet 25, and the underfloor material 20, the rainwater or melted snow water turns into water droplets wd with a contact angle of more than 90 degrees on the upper surface 20a of the underfloor material 20, does not wet and spread on the upper surface 20a of the underfloor material 20, and remains in the above-mentioned gap S1 in the form of water droplets wd. In this way, the water droplets wd remaining in the gap S1 act as a plug, making it difficult for the rainwater or melted snow water to infiltrate further into the gap S1.

[0078] In addition, since the upper layer 21 of the underfloor material 20 has a low water absorption rate (15% or less), even if rainwater or melted snow water penetrates into the gap S1 between the waterproof sheet 25, which has been raised by the vertical materials, and the underfloor material 20 through gaps in the waterproof sheet 25 around vertical materials such as pillars, the penetrated rainwater or melted snow water will simply become water droplets wd with a contact angle of greater than 90 degrees on the upper surface 20a of the underfloor material 20, and will not penetrate into the interior from the upper surface 20a of the underfloor material 20.

[0079] 5A, in a conventional underfloor material 120 using plywood with a high water absorption rate, when water overflows into the floor structure 1 after construction of the floor and the upper surface 120a of the underfloor material 120 becomes wet with water, the water is likely to seep into the space S102 (joint) between two adjacent underfloor materials 120, 120. The water that seeps into the space S102 is absorbed by each veneer from the end of the wood facing the space S102, and permeates into the inside of the underfloor material 120 by flowing in the fiber direction of each veneer.

[0080] In contrast, in the present embodiment 1, as described above, the upper layer 21 of the underfloor material 20 is made of a medium-density fiberboard with low water absorption, and further, the medium-density fiberboard is configured to contain a water repellent agent so that the contact angle of water with the surface is greater than 90 degrees (has water repellency). Therefore, as shown in FIG. 5B, even if water reaches the upper surface 20a of the underfloor material 20 by, for example, spilling water on the floor structure 1 after the floor is constructed, the water becomes water droplets wd with a contact angle greater than 90 degrees on the upper surface 20a of the underfloor material 20, and does not wet and spread on the upper surface 20a of the underfloor material 20. In addition, even if the water droplets wd reach the space S2 (joint) between two adjacent underfloor materials 20, 20, the water droplets wd act as a stopper, making it difficult for water to penetrate into the space S2 (joint). Therefore, with the underfloor material 20 of this embodiment 1, water does not infiltrate into the space S2 (joint) between adjacent underfloor materials 20, as occurs with conventional underfloor materials, and water does not penetrate deep into the interior from the end of the wood facing the space S2 (joint).

[0081] The same applies to rainwater or melted snow water that has infiltrated between the waterproof sheet 25 and the underfloor material 20. Specifically, even if the rainwater or melted snow water that has infiltrated between the waterproof sheet 25 and the underfloor material 20 turns into water droplets wd and reaches the joints of the underfloor material 20, the water droplets wd that have a contact angle with the top surface of the underfloor material of more than 90 degrees act as plugs and the rainwater or melted snow water does not infiltrate into the joints.

[0082] Furthermore, in the conventional underfloor material 120, the nail holes for the nails 5 penetrating the underfloor material 120 have low water-stopping properties, and rainwater or melted snowwater that seeps in between the waterproof sheet 125 and the underfloor material 120 seeps into the nail holes in the underfloor material 120, and moisture is absorbed from the nail holes into the interior of the underfloor material 120 (the inner layer from the surface layer). In other words, the conventional underfloor material 120 has high water absorption, which easily leads to deformation (thickness expansion, warping, twisting) and mold growth in the underfloor material 120.

[0083] In contrast, in the underfloor material 20 of the present embodiment 1, the upper layer 21 is made of a medium-density fiberboard with high nail hole water-stopping properties. Therefore, in either case where rainwater or melted snow water penetrates between the curing waterproof sheet 25 and the underfloor material 20, or where water overflows into the floor structure 1 after the floor is constructed, the infiltrated rainwater, melted snow water, or overflowing water becomes water droplets wd on the upper surface 20a of the underfloor material 20. Even if the water droplets wd reach the nail holes of the nails 5, they act as a stopper and water does not penetrate into the nail holes. Therefore, water does not penetrate into the inside of the underfloor material 20 from the nail holes.

[0084] To verify this, the following permeability test was carried out.

[0085] (1) Test specimen Two of each of the following two types of test specimens X were prepared. I: Medium density fiberboard (thickness 9 mm, density 0.79 g / cm 3 , moisture content 8.9%) II: Plywood (thickness 9 mm, density 0.42 g / cm 3 , moisture content 10.6%, softwood) In addition, the test specimen X in I has a water absorption rate of 15% or less and a moisture permeability resistance of 2.5m, similar to the medium density fiberboard constituting the floor underlayment 20. 2 ·h·mmHg / g.

[0086] (2) Test method First, as shown in FIG. 6, a test tool is assembled. Specifically, a nail 51 (N50, screw nail) is driven into the center of the test piece X from above. A nail 51 of N50 is driven into one of the test pieces X (called test piece X1) of I, and a screw nail is driven into the other (called test piece X2). A nail 51 of N50 is driven into one of the test pieces X (called test piece X3) of II, and a screw nail is driven into the other (called test piece X4). For each of the four types of test pieces X1 to X4 thus formed, a cylinder 52 (inner diameter 34 mm, height 300 mm) made of acrylic resin is placed upright on the upper surface of the test piece X so as to cover the nail 51, and the gap between the cylinder 52 and the upper surface of the test piece X is filled with a caulking agent 53, and then these are placed on a beaker 54 with a diameter larger than that of the cylinder 52.

[0087] After assembling the test equipment, water (at room temperature) was gently poured into the cylinder 52. The water was poured up to a height of 250 mm (approximately 227 ml) in the cylinder 52. The equipment was then left to stand for 8 days in an environment with an air temperature of 20°C and a relative humidity of 65%, and the remaining amount of water, the external appearance of the test specimen X, and water leakage from the nail holes were periodically checked.

[0088] (3) Test results The graph in Fig. 7 shows the results of the water permeability test. The water permeability (ml) shown on the vertical axis of the graph in Fig. 7 is the amount of water that was poured into the cylinder 52. The ■ mark indicates the water permeability of the test specimen X1, the ◆ mark indicates the test specimen X2, the ● mark indicates the test specimen X3, and the ▲ mark indicates the water permeability of the test specimen X4.

[0089] As can be seen from the graph in FIG. 7, among the four types of test specimens X1 to X4, test specimen X4 had the highest water permeation amount, and by the third day after the start of the test, the water in cylinder 52 had almost run out, making it impossible to continue the test. Next, test specimen X3 had the highest water permeation amount, and by the fourth day after the start of the test, the water in cylinder 52 had almost run out, making it impossible to continue the test. From these results, test specimens X3 and X4 In this case, when the nail 51 is driven in, a large nail hole is formed, and it is found that water spreads (penetrates) from this nail hole in the fiber direction of the test piece X and easily passes through the nail 51 to the bottom of the test piece X (beaker 54) (the water-stopping ability of the nail hole is low).

[0090] In contrast, the specimens X1 and X2 constituting the floor underlayment 20 of this embodiment 1 had significantly less water permeability than the specimens X3 and X4 among the four types of specimens X1 to X4, and almost no water flowed out of the cylinder 52 even after three days had passed since the start of the test. In the specimens X1 and X2, water did not drip from the nail 51 into the beaker 54 even after eight days had passed since the start of the test. This is presumably because, in the specimens X1 and X2, the nail 51 is driven into the wood fibers so as to push aside the wood fibers, and the wood fibers coated with adhesive are in close contact with the nail 51, so that almost no gaps through which water can pass are formed. In addition, the specimen X1 is formed with an adhesive containing a first adhesive (in this embodiment 1, a urea-melamine co-condensation resin adhesive) having excellent water resistance, and is configured to have a water absorption rate of 15% or less. Therefore, even if a gap is formed around the nail 51 due to the nail hole, it is presumed that water does not penetrate because the wood fibers are coated with the first adhesive having excellent water resistance. Thus, in test specimens X1 and X2, water did not penetrate from the surface (top surface) to the inside, and did not seep into the nail holes. It is therefore clear that the water permeability is significantly lower than that of test specimens X3 and X4, i.e., the waterproofness is extremely high.

[0091] As described above, in the underfloor material 20 of the present embodiment 1, even if rainwater or melted snow water penetrates between the curing waterproof sheet 25 and the underfloor material 20, or if water is spilled on the floor structure 1 after the floor is constructed, the underfloor material 20 has high waterproofing and is unlikely to absorb water. Therefore, in the underfloor material 20 of the present embodiment 1, even if rainwater or melted snow water penetrates between the curing waterproof sheet 25 and the underfloor material 20, or if water is spilled on the floor structure 1 after the floor is constructed, the underfloor material 20 will not absorb water and deform (expand in thickness, warp, twist), or develop mold.

[0092] In the present embodiment 1, the upper layer 21 of the underfloor material 20 is made of a medium-density fiberboard that is excellent in waterproofing and nail hole waterproofing properties and has water repellency. Therefore, unlike the conventional method, there is no need to carry out special work such as water repellency treatment after construction of the underfloor material in order to suppress deformation and mold growth of the underfloor material.

[0093] -Effects of embodiment 1- In the first embodiment, the upper layer 21 of the underfloor material 20 is made of a medium density fiberboard (MDF) having low water absorption. The medium density fiberboard is a wood board formed by hot pressing wood fibers together with an adhesive to form a board, and has a low water absorption rate. Therefore, even if rainwater or melted snow water penetrates between the waterproof sheet 25 and the underfloor material 20 during construction of a building such as a house (before the construction of the floor finishing material 10), it is not absorbed into the underfloor material 20. In addition, according to such an underfloor material 20, even in the places where the nails 5 are driven in, the wood fibers coated with adhesive are in close contact with the nails 5 driven in so as to push aside the wood fibers, so that rainwater or melted snow water is less likely to penetrate into the nail holes. By using such an underfloor material 20 having excellent waterproofing and nail hole waterproofing properties, even if rainwater or melted snow seeps in between the waterproof sheet 25 and the underfloor material 20 before the construction of the floor finishing material 10, the underfloor material 20 will not absorb the water and deform (expand in thickness, warp, twist), and the growth of mold can also be suppressed.

[0094] In the first embodiment, the medium density fiberboard constituting the upper layer 21 of the underfloor material 20 is configured to contain a water repellent agent so that the contact angle of water with the surface is greater than 90 degrees (has water repellency). Therefore, even if rainwater or melted snow water penetrates into the gap S1 between the waterproof sheet 25 and the underfloor material 20 through the gap in the waterproof sheet 25 formed around the vertical member such as a pillar before the construction of the floor finishing material 10, the rainwater or melted snow water becomes water droplets wd with a contact angle greater than 90 degrees on the upper surface 20a of the underfloor material 20, does not wet and spread on the upper surface 20a of the underfloor material 20, and remains in the above-mentioned gap S1 in the form of water droplets wd. The water droplets wd remaining in the gap S1 act as a plug, making it difficult for rainwater or melted snow water to penetrate further into the gap S1. In other words, by making the upper layer 21 of the underfloor material 20 a water-repellent layer having water repellency, it is possible to prevent rainwater and melted snow water from successively penetrating between the waterproof sheet 25 and the underfloor material 20. Even if the water droplets wd reach the joints of the underfloor material 20, the water droplets wd having a contact angle with the upper surface of the underfloor material of more than 90 degrees act as plugs, and the rainwater and melted snow water do not penetrate into the joints. In other words, by making at least the upper layer 21 of the underfloor material 20 a water-repellent layer having water repellency, it is possible to prevent the penetration of rainwater and melted snow water from the joints of the underfloor material 20.

[0095] Furthermore, in this embodiment 1, by simply using the underfloor material 20 whose upper layer 21 is made of water-repellent medium-density fiberboard, it is possible to easily install the underfloor material 20 with excellent waterproofing, which makes it difficult for rainwater or melted snow water to penetrate between the waterproof sheet 25 and the underfloor material 20 before the construction of the floor finishing material 10, and which does not absorb the water even if it does penetrate, without having to perform special processing work such as spraying water-repellent paint after construction of the underfloor material 20 as in the conventional case.

[0096] Furthermore, in this embodiment 1, the underfloor material 20 has a multi-layer structure having an upper layer 21, an intermediate layer 22, and a lower layer 23, and the upper layer 21 and the lower layer 23 are made of medium density fiberboards that have excellent water repellency and excellent waterproofing and nail hole water stopping properties, while the intermediate layer 22 is made of a honeycomb panel that is relatively lightweight and has high rigidity and has a plurality of holes 22a formed therein, thereby reducing the weight of the underfloor material. By configuring it in this way, it is possible to provide a highly waterproof underfloor material 20 that does not absorb water even if rainwater or melted snow water penetrates between the waterproof sheet 25 and the underfloor material 20 before the construction of the floor finishing material 10, without impairing the workability.

[0097] In addition, in this embodiment 1, an impermeable layer 24 having a lower air permeability than the medium-density fiberboard at the same pressure difference is provided between the medium-density fiberboard (upper layer 21) and the honeycomb panel (middle layer 22). With this configuration, air is less likely to pass through the underfloor material 20 in the thickness direction than when the impermeable layer 24 is not provided. Therefore, with the above configuration, the composite board for the underfloor material 20 can be sucked up (transported) one by one by the suction pad of the suction transport device attached to the precutting machine, and can be precut by the precutting machine. Therefore, according to this embodiment 1, it is possible to provide an underfloor material 20 that has excellent waterproofing and workability and can be precut by the precutting machine.

[0098] Furthermore, conventional underfloor materials using plywood (especially thick plywood with a thickness of 24 mm or more) gradually lose weight over time, causing gaps between the underfloor material and the nails used for construction, which can lead to floor creaking (noises), but in this embodiment 1, the upper layer 21 and lower layer 23 of the underfloor material 20 are made of medium-density fiberboard, which is less susceptible to aging. Therefore, there is no gap between the underfloor material 20 and the nails 5 used for construction, which can cause floor creaking.

[0099] As described above, by constructing the intermediate layer 22 from a honeycomb panel, it is possible to reduce the weight, but the horizontal rigidity is reduced compared to the conventional underfloor material 20 made of plywood. Therefore, if an underfloor material 20 with the intermediate layer 22 made of a honeycomb panel is used, the in-plane shear strength of the horizontal structural member cannot be exerted, and it may be difficult to obtain the so-called existing floor ratio that is recognized for thick plywood.

[0100] However, according to the first embodiment, not only the upper layer 21 that contributes to waterproofing but also the lower layer 23 are made of medium density fiberboard. Medium density fiberboard has high rigidity like plywood, and is also used as a load-bearing surface material for walls and the like. Therefore, by making the upper layer 21 and the lower layer 23 out of medium density fiberboard and then changing their thickness as necessary, it is possible to increase the values ​​of the "short-term standard shear strength" and "existing floor ratio" of the horizontal structural components, which are required to be within a specified range when performing structural calculations, even if the intermediate layer 22 is made of a honeycomb panel.

[0101] In the first embodiment, the underfloor material 20 is not made of only medium-density fiberboard, but is made of a sandwich panel in which an intermediate layer 22 made of a honeycomb panel is sandwiched between an upper layer 21 and a lower layer 23 made of medium-density fiberboard. Medium-density fiberboard has a lower moisture permeability resistance than plywood and the like. However, as described above, by making the underfloor material 20 into a three-layer structure in which a honeycomb panel is sandwiched between two sheets of medium-density fiberboard, the thickness of the medium-density fiberboard can be made thinner than when the underfloor material 20 is made of a single layer of medium-density fiberboard. Furthermore, since the moisture permeability resistance of the honeycomb panel in which the multiple holes 22a are formed is considered to be almost zero, the moisture permeability resistance can be kept low even for the underfloor material 20, which is relatively thick at 20 mm or more.

[0102] In this embodiment 1, the non-breathable layer 24 is provided between the middle layer 22 and the upper layer 21, but since the non-breathable layer 24 is made of paper with a low moisture permeability resistance, the presence of the non-breathable layer 24 does not significantly increase the moisture permeability resistance of the underfloor material 20. Therefore, even if moisture due to rainfall or snowfall is present on the underfloor material 20 before the construction of the floor finishing material 10, the moisture can be easily discharged from the back surface of the underfloor material 20. In addition, even if water is spilled on the floor after the construction of the floor finishing material 10 and reaches the underfloor material 20 through the joints of the floor finishing material 10, the moisture can be easily discharged from the back surface of the underfloor material 20.

[0103] In the first embodiment, the underfloor material 20 is configured such that the intermediate layer 22, which is made of a honeycomb panel that is lighter than medium-density fiberboard, is formed to be thicker than the upper layer 21 and lower layer 23, which are made of medium-density fiberboard. The non-breathable layer 24 is formed to be even thinner than the upper layer 21 and lower layer 23, which are thinner than the intermediate layer 22. With this configuration, the weight of the underfloor material 20 can be further reduced.

[0104] In the first embodiment, the non-breathable layer 24 is made of paper. The non-breathable layer 24 may be made of a resin sheet, or may be made of a non-woven fabric as long as the air permeability at the same pressure difference is lower than that of a medium-density fiberboard. The air permeability at the same pressure difference can be easily adjusted for paper, resin sheet, and non-woven fabric by appropriately changing the density, material, and the presence or absence of coating. Therefore, according to the first embodiment, it is possible to easily configure a non-breathable layer having an air permeability lower than that of a medium-density fiberboard at the same pressure difference.

[0105] In the first embodiment, the intermediate layer 22 is made of a paper honeycomb panel, and the non-breathable layer 24 is made of paper. By making the intermediate layer 22 and the non-breathable layer 24 out of the same material (paper) in this way, the intermediate layer 22 and the non-breathable layer 24 can be easily bonded together using an adhesive suitable for bonding paper.

[0106] In addition, in this embodiment 1, the floor structure 1 uses the above-mentioned underfloor material 20 with excellent waterproofing. Therefore, even if rainwater or melted snow water penetrates between the waterproof sheet 25 and the underfloor material 20 before the construction of the floor finishing material 10, the underfloor material 20 will not absorb water and deform (expand in thickness, warp, twist), and mold growth can be suppressed. Moreover, unlike conventional floor structures, the underfloor material 20 with excellent waterproofing can be easily constructed without performing special processing such as spraying a water-repellent paint after construction of the underfloor material 20.

[0107] Other Embodiments In the above embodiment 1, the floor structure 1 is described as being applied to a floor assembly using a joist-less construction method in which the floor underlayment 20 is fixed to joists or floor beams without providing joists, but the floor underlayment 20 and floor structure 1 according to the present invention can also be applied to a floor assembly using a joist construction method in which joists are provided on joists or floor beams. When applying the floor underlayment 20 and floor structure 1 according to the present invention to a floor assembly using a joist construction method, the floor underlayment 20 may be formed to a thickness of about 12 mm. Even in such a case, the same effect as in embodiment 1 can be achieved.

[0108] Furthermore, the application of the underfloor material 20 and floor structure 1 according to the present invention is not limited to floor assemblies of wooden buildings. The underfloor material 20 and floor structure 1 according to the present invention can also be applied to floor assemblies of buildings made of reinforced concrete, steel frame, steel frame reinforced concrete, etc.

[0109] In addition, in the above embodiment 1, an example was described in which the intermediate layer 22 is constructed of a honeycomb panel in which holes 22a with a hexagonal cross-section are formed. However, the honeycomb panel may be any panel in which a plurality of holes 22a are arranged in a honeycomb pattern, and the cross-sectional shape of the holes 22a is not limited to a hexagonal shape.

[0110] In the above embodiment 1, an example in which the non-breathable layer 24 is provided between the upper layer 21 made of a medium density fiberboard containing a water repellent and the intermediate layer 22 made of a honeycomb panel has been described, but the location where the non-breathable layer 24 is provided is not limited to the above example. The non-breathable layer 24 may be provided between the lower layer 23 and the intermediate layer 22, or between both the upper layer 21 and the lower layer 23 and the intermediate layer 22, that is, above and below the intermediate layer 22. In either case, the same effect as in embodiment 1 can be achieved. In particular, when the non-breathable layer 24 is provided above and below the intermediate layer 22, the underfloor material 20 is configured symmetrically in the thickness direction (vertically symmetrical), so that the underfloor material 20 is less likely to warp. In addition, when the non-breathable layer 24 is provided above and below the intermediate layer 22, the underfloor material 20 becomes more difficult for air to pass through in the thickness direction, so that the composite boards for the underfloor material 20 can be easily sucked up by the suction pad one by one, and it becomes easier to suction and transport them to the pre-cut machine. [Industrial Applicability]

[0111] The present invention is useful for floor underlayment and floor construction. [Explanation of symbols]

[0112] 1 floor structure 10. Floor finishing materials 20 Floor Underlayment 21 Upper layer 22 Middle Class 22a hole 23 Lower layer 24 Non-breathable layer

Claims

1. A floor underlayment material comprising an upper layer, an intermediate layer, and a lower layer, which is applied below a floor finishing material, The upper layer and the lower layer are made of a medium density fiberboard containing a water repellent agent, The intermediate layer is composed of a honeycomb panel having a plurality of holes extending in a thickness direction formed in a honeycomb shape, At least one of between the intermediate layer and the upper layer and between the intermediate layer and the lower layer is provided with a non-air permeable layer having an air permeability lower than that of the medium density fiberboard at the same pressure difference. A floor underlayment characterized by:

2. The floor underlayment material according to claim 1, the upper layer and the lower layer are thinner than the middle layer; The non-breathable layer is thinner than the upper layer and the lower layer. A floor underlayment characterized by:

3. The floor underlayment material according to claim 1 or 2, The non-breathable layer is made of paper, a resin sheet or a nonwoven fabric. A floor underlayment characterized by:

4. The floor underlayment material according to claim 3, The middle layer is made of paper honeycomb panels. The non-breathable layer is made of paper, The non-breathable layer is adhered to the intermediate layer. A floor underlayment characterized by:

5. A floor structure comprising a floor underlayment and a floor finishing material applied on the floor underlayment, The floor underlayment is the floor underlayment according to claim 1. A floor structure characterized by:

Images