Prefabricated shower floor liner for use with solid stone shower floor and method of construction
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A shower installation in which a monolithic stone slab serves as the floor, or pan, of the installation. A liner of plastic material seated beneath the stone slab, the liner in the stone slab each having an aperture therein for receipt of a drain assembly. The liner is formed with an array of channels in the upper surface thereof, all of which slope toward the drain opening in order that fugitive moisture and condensation accumulated beneath the stone slab be directed away from the stone slab and into the drain.

Goodson, Michael J. (Little Rock, AR, US)
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Primary Examiner:
Attorney, Agent or Firm:
Michael Goodson (Little Rock, AR, US)
1. In a shower facility, a monolithic stone floor, said stone floor having a drain opening therein; a liner; said liner having an upper flat surface, a drain opening therein, an array of channels formed in said liner, said groves sloping toward said drain opening; a subfloor, said subfloor having a surface adapted to receive said liner in mating engagement; and a drain assembly disposed in said drain openings such that fugitive moisture and condensation accumulated below said stone slab is directed to said drain through said channels.

2. The shower facility of claim 1, wherein said drain opening is centrally located and both said drain openings being aligned.

3. The shower facility of claim 1, wherein said stone floor slopes towards said drain opening.

4. The shower facility of claim 1, wherein said channels in said liner slope towards said drain opening in order that fugitive moisture is moved to said drain assembly and there disposed.

5. The shower facility of claim 1, wherein said channels define ribs disposed there between.

6. The shower facility of claim 1, wherein said channels are divided into groupings, said channels in each grouping sloping towards said drain opening.

7. The shower facility of claim 5, said ribs having a top edge and all of said top edges of said ribs defining a level surface.

8. The shower facility of claim 7, wherein said monolithic stone floor rests on said level surface.

9. The method of installing a stone slab as a floor in a shower comprising the steps of: a. providing a monolithic stone slab having an opening therein, a series of channels sloping towards said opening; b. providing a liner, said liner formed with an opening and an array of channels formed in the upper surface of said liner, said channels sloping towards said opening; c. forming a bed of initially softened material for receipt of said liner; d. pressing said liner into said softened material, leveling said liner, and allowing said bed to cure and harden with said liner in place; e. affixing said stone slab on the upper surface of said liner such that the openings in each are aligned; and, f. installing a drain in said openings to receive fugitive moisture and condensation accumulated beneath said slab.

10. The method of claim 9, wherein said liner is formed of a plastic material.

11. The method of claim 9, wherein said channels in said liner being in groupings.

12. The method of claim 9, wherein said channels defining ribs there between, said ribs having upper edges, said upper edges together defining a flat surface.


The present invention relates generally to shower floors and, more particularly, to a shower floor liner used in the construction of a shower floor utilizing solid slab stone, while meeting building plumbing code requirements.


1. Field of Invention

Bathroom showers were once viewed for the utilitarian purpose of bathing only. In recent years bathrooms have evolved into luxurious retreat locations designed for beauty, comfort and relaxation. This evolution has created demand for beautiful and durable materials for use in all areas of bathroom design. This is particularly true in the case of the shower. The shower, once viewed as simply an area in which to bathe, is now considered an integral part of an overall spa environment designed for comfort, beauty and durability.

Natural stone has become the designer's choice as the preferred material from which to construct long lasting, durable, yet beautiful showers. Natural stone, while having the desirable benefits of beauty and durability, has the inherent characteristic of being porous and having minimal flexural-strength causing stone to fracture when placed under bending loads. It is these two characteristics which must be dealt with when using natural stone as a material for construction of a shower floor.

Of critical concern when choosing materials and construction methods to build a shower is keeping areas adjacent to and below a shower from accumulating moisture. Building plumbing codes require that a waterproof membrane be installed below any shower floor constructed from porous material. It is the purpose of the waterproof membrane to capture any water which may pass through a porous floor preventing water contamination to surrounding areas. It is a further building code requirement that the waterproof membrane be installed over a pre-sloped floor and the membrane be attached to a drain allowing fugitive moisture to escape.

2. Overview of Prior Art

Until recently the construction method for a shower floor when using natural stone as the surface material involved the installation of stone tile [as distinguished from a slab of stone] over the pre-sloped floor. Pre-sloping of the floor to receive the tile can be accomplished by hand troweling thin-set mortar to the desired slope, or by installing a pre-manufactured sloped liner designed to receive tile on its surface. Gerber patent 5,913,777 is an example of this method.

In either of the above installation methods, an additional layer of hand laid drypack mortar must be applied on the surface of the waterproof membrane. It is this final drypack layer that provides the finished surface to which tile is glued. Once tile is glued into place, grout (a mixture of Portland cement, water and dye) must be applied to the tile surface, filling all voids remaining between each piece of tile.

Further descriptions of the common installation methods for stone tile can be reviewed in Stone World Magazine, July 2008 edition, page 266 entitled “Tips for Stone Shower Installations”.

Additional insight as to proper installation of stone tile shower floors can be obtained by a review of the Tile Council of North America (TCNA) illustration B-415. Schulter Systems L.P. of Plattsburg, N.Y. has published a CD demonstrating a method for installing a waterproof barrier in preparation for a tile shower floor.

Other techniques for building showers are found in Gerloff patent 6,571,406, which involves a prefabricated shower module. Also see Hansenkopf publication US 2001/0052148, and German patent publication DE 200 04764 U 1, which relates to the use of a stone shower floor.

It will be appreciated that all of the above methods and devices are labor intensive and unduly complex to install, while providing minimal protection. Finally, tile and the grout joints associated with tile installations have the disadvantages of being difficult to maintain (clean), fostering the growth of mold and are subject to cracking, allowing water to easily pass through the finished surface.


The focus of the present invention is on the provision of a shower floor liner, the principal objective of which is to permit the use of a solid slab stone in place of stone tile, thereby eliminating the problems attendant the use of stone tile, including the elimination of the need for grout.

A further objective of the present invention is to provide a monolithic waterproof barrier which complies, in every respect, with all applicable building codes. Another objective, related to the foregoing, is the elimination of a code requirement that a pre sloped floor be provided.

Yet another objective related to the foregoing, is to minimize excessive labor costs associated with typical stone tile installations.

Still another objective is to provide both material and method for creating a waterproof barrier, when using a solid stone slab as a shower floor, which will capture and evacuate any fugitive moisture passing through the stone.

The foregoing objectives and advantages will become apparent from a reading of the Detailed Description of a Preferred Embodiment, in conjunction with the drawings, wherein:


FIG. 1 is a sectional view of a typical stone tile shower floor with a pre-sloped floor and a waterproof membrane connected to the drain and is illustrative of the prior art stone shower using stone tile;

FIG. 2 is a top plan view of a monolithic stone pan, or floor, for use in constructing a stone shower floor in accordance with the present invention, illustrating the structure of a solid slab;

FIG. 3 is a sectional view taken through lines 3-3 of FIG. 2; a stone shower floor with the upper surface sloping to a drain opening;

FIG. 4 is a top plan view of a shower floor liner constructed in accordance with the present invention and which makes the use of a monolithic stone slab especially valuable as a shower floor;

FIG. 5 is a partial cut away sectional view illustrating the interrelationship of the various elements which make up a shower installation in which the floor is a solid slab stone installed over a pre-sloped floor with the novel liner of the present invention interposed immediately beneath the stone floor; and

FIG. 6 is a sectional view illustrating the structure of a solid slab stone shower floor installed in accordance with the present invention.


The present invention is the culmination of substantial study and experimentation aimed at exploiting the substantial benefits of using a solid stone slab as a shower pan or floor.

With the objectives in mind, reference is made to the drawings and, initially to FIG. 1, in which the current construction of a shower using stone is illustrated in some detail. The stone currently in use is in the form of tile, with all of its deficiencies, as distinguished from a monolithic stone slab, the employment of which is the focus of the present invention.

Still referring to FIG. 1, an array of stone tiles 10 is positioned over a pre-sloped floor 12 and along a side wall 14. The tiles are secured in any well known manner, such as by dry pack mortar and grout.

The procedure for installing a stone tile shower, such as shown in FIG. 1, is both tedious and time consuming. The installer must first build the pre-sloped floor, by building the floor with a thin set mortar to slope the floor to the drain 16. After allowing the mortar to cure for 24 hours, a waterproof member is applied over a pre-sloped floor. Next, the installer applies a layer of dry pack mortar above the waterproof membrane, and, once again, it must set for 24 additional hours. Next, the installer lays the stone tile using any suitable mastic material, and yes, allows it to cure for another 24 hours.

Grout is used to fill the voids between the stone tile, and the tile is washed down to remove excess grout.

In rather stark contrast, the use of a monolithic stone slab enhances the beauty of the installation while simplifying the process. The genesis of the installation of the present invention rests with a stone slab or pan 20, shown in FIG. 2. The face of the stone slab 20 is machined to slope toward the drain opening or aperture 24. It may be roughened slightly to make it non slip. The underside 26 of the slab 20 is flat. It will be appreciated that this stone floor 20 does not require the application of grout as the stone surface is one solid piece. This surface is also much easier to clean and will not foster the growth of mold. Beyond the practical advantages, it is exceptionally pleasing to the eye.

A key to using a monolithic slab of stone, while meeting all of the code requirements, is the novel liner 30 of the present invention as seen in FIG. 4. The liner 30 is a single unit, molded, or cast, preferably of a plastic material, in any of several well known methods, and the surface is formed with a series of channels 32 each of which slopes to the drain. Adjacent channels define upstanding ribs 33, the top edges of which collectively define a flat surface 34 which will eventually support a stone floor. All of the channels 32 slope toward a drain opening or aperture 36, where a drain assembly 40 is positioned for receipt of drain water from the stone slab 20, and, of course, the liner 30 during use.

For efficiency and simplicity in the molding process, the channels 32 are divided into four substantially identical groups 38. Each channel is designed to capture fugitive moisture and direct it to the drain where it is drained away from the installation. The groupings 38 of the channels 32 make it simple to capture moisture where ever it occurs, directing it straight to the drain where it is disposed of in a straight forward manner.

Addressing the completed installation as seen in FIGS. 5 and 6, the interrelationship of the various elements is clearly shown. The solid slab stone floor 20 is seated over the monolithic liner 30, where it is supported on the level surface 34, defined by the supporting ribs 33.

The present invention contemplates an adjunct to the liner 30 in the form of an upstanding splash guard 45. The splash guard 45 is a flexible liner comprising a single sheet of a flexible moisture impermeable material which is glued about the perimeter of the liner 30, where it is attached to conventional wall framing 51. Finish wall 53, and backer board 52 provide an initial barrier to moisture, and splash guard 45 provides a further barrier to moisture which might otherwise migrate, or condense, to promote mold and rot beneath the installation.

The installation thus described is efficiently assembled and integrated into existing conventional construction either as an original construction or as a remodel. With FIGS. 5 and 6 as a guide, a proper installation involves initial preparation of a bed of softened thin-set mortar, applied uniformly over the entire area to be covered by liner 30. Next, install monolithic liner 30 over the entire area of the mortar bed. It is important that liner 30 be installed level. This is accomplished by using a carpenter's level and applying pressure to the high areas of liner 30 while the mortar bed is still wet. The mortar bed is now allowed to cure (harden).

It is now time to install the solid slab stone floor 20 on the surface 34, defined by the ribs 33, of the monolithic liner such that the respective drain openings are aligned. Finally, the upstanding flexible liner 45 is attached to the adjacent wall framing 51, and the installation is complete and fully compliant with all codes relevant to the project.

It will be appreciated that those skilled in the art may perceive minor variations in the structure and the method of achieving it. It will be understood, however, that such variations are within the contemplation of the invention as defined by the claims wherein: