US 3549471 A
Description (OCR text may contain errors)
Dec. 22, 1970 c. "r. BENTON LAMINATED MATERIALS FOR COVERING SU RFACES OF BUILDINGS Filed Se t; 14, 1967 2 Sheets-Sheet 1 V/V 4/ ///l I,
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9 c. T. DENTON 3,549,471
LAMINATED MATERIALS FUR COVERING SURFACES 0F BUILDINGS Filed Sept. 14, 1967 2 Sheets-Shoot 2 11. .8 157 Ifi 4%; J/WEA/YQR United States Patent 3,549,471 LAMINATED MATERIALS FOR COVERING SURFACES OF BUILDINGS Clyde T. Denton, Los Angeles, Calif., assignor to Resilient Services Incorporated, Los Angeles, Calif., 21 corporation of California Filed Sept. 14, 1967, Ser. No. 667,705 Int. Cl. B32b 3/00 US. Cl. 161-86 Claims ABSTRACT OF THE DISCLOSURE An underlayer for floor or wall coverings is prepared by permanently bonding upper and lower continuous layers, typically of impregnated muslin, to a membrane that is slotted to accommodate dimensional changes due to moisture, heat, cold and the like, the cover layers preventing filling of the slots with adhesive during application.
Tile units are made up with such a composite underlayer on one face. After laying, such tiles are unified by an overcoat of fully compatible material that fills cracks between tiles.
Base and border assemblies utilize a similar underlayer, and may include a flexibly joined tack bar for securing a carpet. Flexible cove structures may be lifted to insert a carpet edge. Improved fit between the base and border assembly and the field covering is secured by means of tapered shim stock that extends from the border under the field covering.
Fit between sections of base is facilitated by an overlap with the front flange longer than the back flange.
This invention has to do with materials and methods for covering surfaces of buildings. The invention is concerned particularly, but not exclusively, with covering floors and the adjoining base areas of walls.
A primary object of the invention is to obtain smooth and reliable bonding between the building surfaces and the covering materials despite unevenness of the building surfaces and despite expansion and contraction of any portion of the covering materials due to dampness, heat, cold and similar causes.
An important aspect of the invention relates to the accommodation of the expansion and contraction of the protective membrane that is customarily installed between the building surface and the main elements of the covering. Such a membrane is often formed of felt or other fibrous material that tends to swell in presence of moisture or heat. Normal impregnation of such a membrane with water resistant materials such as asphalt, for example, does not entirely eliminate the variable diffusion of moisture when the covering is laid on surfaces such as concrete, for example. I have previously described a method of preventing the resulting expansion and contraction of the membrane from producing buckling of the floor covering by providing the membrane with a plurality of mutually spaced, multi-directional slots that accommodate lateral movements of local areas of the membrane. My Pat. 2,556,071 describes a particularly effective slot structure for that purpose. The present invention provides more convenient and economical materials and methods for utilizing such slotted membranes, leading to greater ease of installation and longer life of the resulting covering assemblies.
One aspect of this invention provides a laminated subassembly comprising a slotted membrane with upper and lower layers of muslin or like material so bonded to its opposite faces that the membrane slots remain reliably hollow and unfilled by the bonding agent. Such a sub- Patented Dec. 22, 1970 'ice assembly can be applied to a building surface, and a covering layer then adhered to its outer face, by rapid and economical conventional procedures, since precautions are not required to prevent filling of the membrane slots with adhesive.
A further aspect of the invention provides tile units of interfitting geometrical shape having a membrane of the described type integrated with them, preferably in a manner that provides overlap between adjacent units. Such tile units are conveniently assembled to form an effectively continuous covering for a fioor or other building surface with the additional advantage of accommodating expansion and contraction that may be caused by moisture, heat, cold and the like.
The invention further provides improved types of integrated base and border for a floor area, which are economical to apply, adhere reliably to the building surfaces and provide accurate and reliable fit and alinement with the field covering. Such base and border assemblies may be designed to receive any desired type of field covering, including, in particular, individual tile units, vinyl carpet materials, and conventional carpets, as well as field coverings produced by wet pouring on the job.
In laying a carpet, for example, in conventional practice the edge portion of the carpet is ordinarily secured by engaging hook formations of a tack strip which is fastened directly to the floor. A plain base strip may be cemented to the wall either before or after the carpet is installed, but generally leaves an unsightly and unsanitary crevice. That difficulty may be largely overcome by employing a cove base with curved lower portion adapted to overlie the edge portion of the carpet. However, if such a base is applied before installation of the carpet, the carpet edge must be tucked under the cove base, tending to pry the base away from the wall; while later application of the cove base risks damaging the carpet with adhesive.
One aspect of the present invention overcomes those difiiculties by providing a combined base strip and tack bar which is readily installed as a single operation, permits convenient placement or removal of the carpet, and provides a stronger and more reliable fastening than was normally obtainable with previously available structures.
The invention further provides improved base and border assemblies with integrated coving. One form of such assembly permits particularly convenient and secure installation of carpet floor covering in the field area. Other forms are particularly adapted for field covering employing tile units, and can be cut after installation to fit varying field dimensions.
A further important feature of the invention provides a tapered shim-like flange that extends along the fioor from the edge of the border and underlies the periphery of the field covering material, whatever the nature of the latter. Such shim structure insures level fit between the border and field despite irregularities of the floor surface, greatly facilitating installation and improving the quality and durability of the job.
A further aspect of the invention provides an especially smooth and uniform and essentially unitary surface particularly well suited for floors. That is accomplished by applying over the main floor covering a coat of liquid polymerizable resin, preferably of the same type that is embodied in the main floor covering, and allowing it to polymerize in position. Such an overlayer is especially useful in connection with a fioor covering of assembled units, such as the tile units of the present invention, for example. When so applied, the overlayer is preferably caused to penetrate the cracks between the covering units, essentially unifying them into a continuous, completely seamless and water impervious covering.
A full understanding of the invention, and of its further objects and advantages, will be had from the following description of certain illustrative manners in which it can be carried out. The particulars of that description, as of the accompanying drawings which form a part of it, are intended only as illustration, and not as a limitation upon the scope of the invention, which is defined in the appended claims.
In the drawings.
FIG. 1 is a schematic perspective illustrating one aspect of the invention;
FIG. 2 is a schematic perspective representing a tile unit in accordance with the invention;
FIG. 3 is a section at enlarged scale, taken as indicated by the line 3-3 of FIG. 2 and representing a modification;
FIG. 4 is a fragmentary section at further enlarged scale, representing a completed floor covering utilizing tile units in accordance with the invention;
FIG. 5 is a schematic perspective representing a base structure in accordance with the invention;
FIG. 6 is a fragmentary section illustrating typical installation of a modified base structure;
FIG. 7 is a fragmentary section representing a further,
modified base structure;
FIG. 8 is a section illustrating typical installation of the base structure of FIG. 7;
FIG. 9 is a schematic perspective representing a base strip and tack bar assembly in accordance with the invention;
FIG. 10 is a section at enlarged scale on line 10-10 of FIG. 9; and
FIG. 11 is a schematic perspective representing a modified base strip and tack bar assembly.
FIG. 1 represents schematically one embodiment of the present invention, comprising an integrated sandwich structure of three layers. The middle layer 32 is a flexible membrane, typically of fibrous material such as felt, for example, made water-resistant by saturation with a non-fibrous water-impervious material such as a polymerized epoxy or vinyl resin having suitable flexibility. For some purposes membrane 30 may comprise a synthetic resinous material without any fibrous component. Membrane 30 is pierced by a plurality of narrow, mutually spaced, vari-directional slots 34, which may be grouped to form the zig-zag patterns indicated at 36.
The upper and lower layers 38 and 39 of assembly 30 comprise continuous sheet material, typically conventional muslin impregnated with polymerized epoxy or vinyl resin, which is firmly bonded to the respective faces of membrane 32. That bond is typically produced by wetting the opposing surfaces of the two muslin layers 38 and 39 with adhesive in the form of liquid polymerizable resin of the same type as that impregnating the muslin and membrane 32, rolling the three layers together, and allowing polymerization of the liquid to essentially integrate the three layers into a single unified sheet. The amount of such liquid applied is carefully limited to prevent filling the slots 34 of the membrane, so that after integration the slots form sealed hollow chambers unfilled by resin or any other adhesive material that is used. The membrane assembly of FIG. 1 may be fabricated and sold in large sheets, or preferably as long strips supplied in rolls, as indicated at 35.
Slots 34 are made narrow enough to insure effectively continuous support for the covering sheets of muslin or the like at 38 and 39. However, even very narrow slots, particularly when formed in zig-zag patterns as illustrated, are capable of accommodating any expansion or contraction of the flexible membrane that normally results from diffusion of moisture or from heat, cold or other causes.
The present membrane assembly 30 has the great advantage that it can be adhered to a wall or floor surface as an underlayer for any desired covering material Without requiring care during such assembly to avoid filling the slots 34 with adhesive. The muslin layers 38 and 39 protect the slots and also provide a good bond with any normally used adhesives, which can therefore be handled in conventional manner without special precautions.
FIGS. 2 and 3 illustrate schematically a tile unit 40 in accordance with the present invention. The numeral 42 designates a tile element of any desired kind, typically a conventional resilient covering material such as polymerized resin, or a vinyl carpet, for example. Element 42 is of such geometrical shape that tile elements can be assembled together to form a continuous covering layer for a floor or other building surface. That shape may, for example, be rectangular, triangular, diamond-shaped or hexagonal, being shown rectangular for illustration. Tile element 42 is firmly bonded to a support assembly 44 comprising a membrane layer 45 sandwiched between upper and lower protective layers 46 and 47. Membrane layer 45 is like membrane 32 already described in connection with FIG. 1, and is preferably similarly slotted. Layers 46 and 47 are typically of muslin, impregnated as described in connection with layers 37 and 38 of FIG. 1. Support assembly 44 is typically of the same shape and size as tile element 42, but is offset diagonally with respect to the latter to provide flanges 50 and 51 adapted to overlap between adjacent tile units on assembly. The upper faces of the support flanges 50 and the lower faces of the tile element flanges 51 are preferably provided with pressure sensitive adhesive to facilitate binding the adjacent tile units togther on assembly. Such adhesive is indicated in FIG. 3 as comprising an adhesive layer 52 and a smooth protective strip 53 that is peelable from layer 52 in conventional manner just prior to assembly of the units.
In the manufacture of tile units of the type shown in FIGS. 2 and 3, it is convenient to prepare the support assembly 44 initially in the form of large sheets or rolls of sandwich structure, as described in connection with FIG. 1, and to cut support units of the desired size and shape from that sheet material for assembly with the tile units 42. The latter may be cut from sheet material, cast to shape from polymerizable material, or formed in any other suitable manner. The tile unit and support assembly may be joined with any suitable adhesive material, preferably resin cement of the same type employed in base 44. When the building surface to be covered is subject to heavy wear it is often desirable to employ a tile 42 of composite structure, as indicated in FIG. 3, comprising a main layer 48 of conventional resilient covering material with a surface layer 49 of polymerized epoxy or vinyl resin, which may be precast and combined with the main layer by means of a film of polymerizable liquid resin.
The tile units of FIGS. 2 and 3 can be installed on the building surface to be covered by means of any suitable adhesive, the lower layer 47 providing a satisfactory tooth for bonding with the adhesive. After placing of each unit, the pressure sensitive adhesive layer 52 on the flange 50 is exposed by removal of cover layer 53. Before placing the adjoining tile unit, the pressure sensitive adhesive layer on the lower face of flange 51 is similarly exposed. Upon contact of the two exposed adhesive layers, they form a strong bond, effectively unifying the several units. After all the tile units have been placed, the surface is preferably coated with a layer of liquid polymerizable resin of the same type that was employed in fabricating the tile units. That layer is shown illustratively at 56 in FIG. 4. It should be thick enough to provide ample liquid to penetrate any remaining crevices between tile units, as indicated at 58 and 58a. Upon polymerization of that liquid, there results continuous, impermeable and highly integrated covering structure.
FIG. 5 represents a coved base structure 60 which is provided with a shim stock extension in accordance with the present invention. The base strip 62 is typically molded of a Water impervious, slightly flexible material such as rubber, linoleum, a conventional polymerized epoxy or vinyl resin, or similar material. It has a smooth front face curving back at the top to a sharp top edge 61 that is resiliently prestressed in a rearward direction to fit tightly against a wall surface and accommodate slight irregularities in that surface. Conventional grooves 61a are provided in the rear face of the base strip near the top edge to trap excess adhesive. The base strip is provided with the coved region 63 terminating in the short toe region 64 with edge 65. Beyond the toe edge 65 the shim stock 66 extends adjacent the floor surface. The thickness of shim stock 66 where it first emerges from base edge 65 is only sufficient to give it the required strength, and that thickness tapers gradually essentially to zero at the shim edge 67. The shim stock is preferably integral with the backing layer 68, which covers essentially the entire contact face of base 62 and may be of conventional type. If backing layer 68 is muslin, for example, impregnated with water impervious material such as polymerized resin, the main body of shim stock 66 may comprise an extension of that impregnated muslin. The tapered edge portion of the shim stock can then be formed of polymerized resin of the same type as that impregnating thei, muslin, of which it constitutes an integral extension.
FIG. 6 illustrates typical installation of the base assembly of FIG. at the corner between a typical building floor 70 and wall 72, and further illustrates modified toe structure. The floor surface is shown with a local depression at 73, exaggerated for clarity of illustration, the normal floor level being represented by the dashed line 74. The base assembly is installed with conventional adhesive and/or filler materials, represented by the numeral 76. That adhesive and/or filler fills the corner area 7611 back of the cove region 64 of the base and also fills floor depression 73. Aside from those regions, the adhesive layer is, of course, very thin, but is exaggerated in the figure for clarity of illustration.
As used herein, the expression field is intended to include floors, walls and other interior surfaces of buildings.
The field area of the floor is covered by a typical floor covering, represented at 78. That covering o'verlies shim stock 66 of the base assembly, and abuts base edge 65. Due to the inherent stiffness of base 60, caused in large part by the curve of the cove region, the toe area of the base tends to bridge the floor depression 73, as illustrated. On the other hand, the edge portion of the field covering, if it were not supported by the shim stock, would sag into floor depression 73. That would cause misalinement between the field and the toe region of the base, exposing an unsightly and unsanitary corner at edge 65. However, with shim stock 66, as illustrated, the edge of the field covering is reliably held in proper alinement with the base toe despite irregularities in the floor surface.
Field covering 78 is shown in FIG. 6 as a carpet 77 laid on the padding layer 79. The toe of base 60 is recessed to form the lower edge face 65a, of suitable height to about padding layer 79, and the upper edge faces 65b which receives the edge of the carpet proper. The carpet is anchored to the shelf 80 of base 60 by means of the pins 81, set obliquely in the base at the time of manufacture. The metal trim strip 82 may be added if desired, and is typically fastened to shelf 80 by the screws 83, covering the pin ends and retaining the carpet more securely on the pins.
The base structure shown in FIG. 6 is also well adapted for receiving field covering material that is wet poured on the job. Shelf 80 provides a convenient guide surface for the major fill, which adjoins edge 65a, while the topping layer of the fill covers the shelf and adjoins edge 65b. The resulting ship-lap effect insures accurate and desrable alinement of the field and base surfaces. Pins 81 may be omitted, or may provide further reinforcement of the joint between field and base.
FIG. 7 represents a modified base structure in which a slotted membrane 84 has been integrated. Such a membrane may be included also in the structures of FIGS. 5
and 6. As illustratively shown in FIG. 7, membrane 84 is adhered directly to the back surface of base 62, typically by employing as adhesive a liquid polymerizable material of the same type of which the base is formed. Base strip 62 is preferably recessed to receive the membrane, as indicated at 86, with the membrane limited to the base and cove portions of the base strip, where the accommodation of expansion and contraction is most often required. Membrane 84 is covered by a suitable protective and bonding layer 68, typically of muslin or the like. That layer preferably leads directly into the shim stock extension 66 in the manner already described in connection with FIG. 5. In cementing layer 68 to membrane 84, as in assembling the membrane to the base strip, care is taken to avoid filling the membrane slots 85 with adhesive, as already described.
A further aspect of the invention relates to a base assembly structure that is particularly adapted for use with a field covering that has an inherent dimensional limitation, so that the toe region of the base must conform to the field dimension. For that purpose the toe region 88.of the base strip is formed of relatively flexible material. Moreover, though directly overlying shim stock 66, the base toe region is separable from the shim stock for an appreciable distance back from the toe edge, as indicated in FIG. 7 by the dashed lines 88a. The toe edge is preferably rounded, as indicated at 89. That manner of construction permits the following highly convenient and effective procedure for installation. The base assembly is first secured in place essentially in conventional manner, typically by application of suitable adhesive between muslin layer 68 and the wall surface and between shim stock 66 and the floor surface. During that installation, toe region 88 of the base strip is allowed to overlie the shim stock directly, tending to hold the latter accurately fiat so that any irregularities in the floor surface will be filled by adhesive, essentially as illustrated in FIG. 6-. The rounded toe edge 89 tends to prevent damage to the base after such installation and before installation of the field covering material. For installation of the field, toe region 88 of the base strip is lifted, as in FIG. 8, permitting the field covering 90 to be inserted under it but above shim stock 66. The field covering edge 92 is therefore supported on an accurately flat surface, independently of minor variations of the floor surface. The exact position of the field edge 92 is assumed to be determined by the field structure. For example, the field covering may be conventional resilient sheet material having a pattern that limits the edge position; or the field may comprise tile units that are preferably not broken at the edge. Such a variable position of edge 92 is accommodated, after installation of the field covering as in FIG. 8, by cutting the toe of the base to fit the laid field. That may conveniently be done by scribing the upper face of the base strip at 94 with a conventional instrument guided by edge 92 and then hand cutting the base at 95 to the scribed line. Toe region 88 is then cemented down to shim stock 66, giving an accurate fit with the field covering as indicated at '96. Adhesive layers are omitted in FIG. 8 for clarity of illustration.
A combined base strip and tack bar in accordance with a further aspect of the invention is represented at in FIG. 9. The base strip proper is indicated at with the main body 111 of molded water-impervious material, the membrane 112 slotted at 113 (see FIG. 11), and the protective and mounting layer of muslin or the like 114, formed and structurally integrated in a manner similar to that described in connection with FIG. 7, for example. Base strip 100 is preferably formed with readwardly prestressed top edge 116 and adhesive retaining channels 118. The bottom edge of the base strip is not coved, but is beveled as indicated at 120 to permit a snug fit to the floor and wall surfaces despite roughness or irregularity of the corner between them. Backing layer 114 extends forwardly from the bottom edge of the base strip, as shown at 122.
The tack bar 130 may be of conventional wood construction or other suitable material with prongs 134 extending obliquely from its upper face. The tack bar has its lower surface firmly bonded to the muslin extension 122 in parallel relation to the base strip but spaced therefrom by a narrow gap indicated at 132. The free strip of muslin at 123 between the tack bar and base strip forms a flexible hinge structure that accommodates slight irregularities in the floor and wall surfaces, and permits folding of the assembly for more convenient storage and handling prior to use.
The combined base strip and tack bar is installed prior to laying the carpet or similar floor covering. Base strip 110 is adhered to the wall surface by any suitable adhesive, which may be applied in conventional manner without danger of filling the slots 113 of membrane 112. Tack bar 130 may also be adhered to the floor, though for some installations the tack bar is retained in position sufiiciently firmly by muslin hinge 123. Conventional carpet padding is typically laid on the floor up to the tack bar, and the carpet installed in normal manner, firmly abutting the front face of base strip 110. The carpet edge may be bent downward into the channel 132 between the tack bar and base, giving a neat and finished appearance.
FIGS. 9 and 10 illustrate further aspect of the invention, whereby improved fit is obtained at the vertical junctions 140 between adjacent sections of base strip. The ends of the sections are flanged, as shown best in FIG. 10, in a manner providing an overlap at the joint. The flat contact faces at 142 tend to define the front faces of both sections, permanently retaining them in accurate and smooth alinement despite slight wall irregularities. Furthermore, front flange 143 is made appreciably longer than rear flange 144. Under normal installation, with completely true wall and floor surfaces, that merely produces a vertical open channel 146 at the back of the base strip, causing no difficulty. On the other hand, unevenness in the floor surface sometimes requires that adjoining sections of base depart slightly from strict parallelism in a vertical plane. With the present construction such departure from parallelism can be accommodated by suitable slightly oblique trimmings of the end face 148 of front flange 143 of one base section. Rear flange 144 of the adjacent base section does not require corresponding trimming, except in the rare case in which more material must be removed than the width of rear channel 146.
The structure shown in FIG. 11 differs from that of FIG. 9 mainly in providing a cove strip 150, which is mounted on base strip 110a at 152 and is preferably essentially integral therewith. Cove strip 150 is joined to the base strip at an area 152 of the latter intermediate its upper and lower edges, curving downward and outward therefrom in a tangential manner. The free edge 154 of cove strip 150 is tapered and curved downwardly in a manner to abut directly against the upper surface of an installed carpet or other field covering material. A typical carpet is shown at 160, with underlying carpet pad at 166. The cove strip is constructed in such a way that it is resiliently flexible with respect to transverse bending, so that the free edge 154 can be lifted an inch or two above the carpet surface, as indicated in dot-dash lines at 150a, and will return resiliently when released to the position shown in solid lines. Such resilience is obtainable by selection of a suitable type of polymerized resin material, typically different in composition from the main body of base strip 110a, but compatible with it and capable of forming an eflectively unitary structure. However, I prefer to enhance the resilience and strength of cove strip 150 by embedding in it a metallic resilient core 156. That core is typically of relatively thin sheet material, as indicated at 157, and preferably has deeply serrated edges, as indicated at 158, giving the core a Zig-Zag pattern as seen in plan. With that composite. structure of resilient metal core embedded in a homogeneous body of suitable polymerized resin, the cove strip may be light in weight, effectively flexible to facilitate installation of the carpet, and yet strongly resilient to insure a firm and tight contact with the carpet after installation.
A combination base strip and tack bar with cove strip as shown in FIG. 11 is typically installed as already described with reference to FIGS. 9 and 10. Carpet pad 166 is then laid on the floor, and the carpet is installed over it. The carpet edge is preferably cut somewhat oversize. By lifting the cove strip as indicated at 150a, the carpet edge is readily inserted beneath it and secured to the prongs 134 of the tack bar. The surplus carpet is folded back, as shown at 162, within the chamber 164 of generally triangular section formed by the cove strip, tack bar and base strip. The resilience of that folded carpet tends to enlarge the chamber, thus pressing the lower part of the base strip toward the wall, supporting the intermediate portion of the cove strip, and retaining the carpet securely on prongs 134.
1. An integrated assembly applicable as a unit to a surface of a building as at least a partial covering therefor, comprising in combination a membrane of material that tends to swell when exposed to heat or dampness, pierced by a plurality of narrow, mutually spaced, variously directed slots to accommodate lateral movement of local membrane areas relative to each other,
a substantially dimensionally stable, water impervious layer adhered permanently to the upper face of the membrane,
and a muslin sealing layer impregnated with water impervious synthetic resinous material to form a continuous sheet, adhered permanently to the under face of said membrane and adapted to be bonded to a building surface by a conventional adhesive,
the membrane slots forming hollow chambers unfilled by bonding material and sealed by said layers.
2. An assembly as defined in claim 1 and in which said dimensionally stable layer comprises muslin impregnated with substantially the same synthetic resinous material as that impregnating the first said muslin layer.
3. An assembly as defined in claim 1 and in which said dimensionally stable layer comprises an interlayer of muslin impregnated with water impervious synthetic resinous material and an overlayer of resilient covering material.
4. An assembly as defined in claim 1 and in which said dimensionally stable layer consists essentially of a resilient covering material adapted to be applied to a wall along the base thereof, whereby said assembly forms a base strip.
5. An assembly as defined in claim 4 and including also a tack bar in spaced parallel relation to the base strip, and a flexible hinge structure bridging the space between the tack bar and base strip and flexibly connecting the same, said tack bar comprising an elongated strip of solid material carrying anchor formations for attaching the edge of a carpet.
6. An assembly as defined in claim 5 and in which said flexible hinge structureconsists essentially of an integral extension of said muslin layer.
7. An assembly as defined in claim 1, and in which said dimensionally stable layer has the shape of a right dihedral angle with a fillet between the sides of said dihedral angle, whereby said assembly is adapted to be applied to a wall at the base thereof and to the floor immediately adjacent to said wall.
8. An assembly as defined in claim 7, wherein said dimensionally stable layer is gradually reduced in thickness to a sharp edge along the portion adapted to be applied to the surface of a floor.
9. An assembly according to claim 7, and in which the side of said dihedral angle adapted to be applied to the surface of a floor is cut back from its edge for only a portion of its thickness to form a shelf and a secondary edge, the leading edge of said side being adapted to abut a pad for a field covering and the secondary edge being adapted to abut a field of covering layer.
10. A generally fiat covering unit for covering a unit area of a surface of a building, comprising in combination a membrane of material that tends to swell when exposed to heat or dampness, pierced by a plurality of narrow, mutualy spaced, variously directed slots to accommodate lateral movement of local membrane areas relative to each other, an upper muslin layer and a lower muslin layer impregnated and bonded to the respective membrane faces with water impervious synthetic resinous material, the memberane slots forming closed chambers unfillled by the resinous material, a tile of solid, slightly flexible, wear-resistant covering material bonded to the upper muslin layer, the membrane, muslin layers and tile all having essentially the same geometrical shape such that like units interfit to form a continuous covering. the membrane directly overlying the lower muslin layer,
and at least the tile being offset diagonally with respect to the membrane and lower muslin layer to form laterally extending flanges providing overlap between all adjoining edges of adjacent units.
References Cited UNITED STATES PATENTS JOHN T. GOOLKASIAN, Primary Examiner W. E. HOAG, Assistant Examiner U.S. C1. X.R.