Abstract:
A barrier to fluid passage is embedded within, instead of atop, porous material to retain the durability of the surface of the porous material. In one embodiment, a thin set mortar is applied to a concrete slab. A pleated metal foil is pressed into the wet mortar and a bond is established. The mortar is allowed to set and a top, or finish, section of concrete is then poured over the foil and finished conventionally. Provisions are made for sealing expansion joints in concrete slab floors and at the juncture of floor and wall. The foil may be provided in multiple layers to provide a mechanical bond via mortar oozing through perforations or along pleats in each of the top and bottoms layers, while providing a solid layer through which a fluid will not pass, at least in one direction.

Description:
RELATED APPLICATIONS 
       [0001]    This application is a division of U.S. patent application Ser. No. 11/368,473,  Method of Implementing Waterproofing under a Concrete Surface Coat of a Concrete Floor,  by McInerney et al., filed Mar. 7, 2006 which is, in turn, a division of U.S. patent application Ser. No. 10/715,430 , Embedded Barrier to Fluid Flow,  by McInerney et al., filed Nov. 19, 2003, both of which are incorporated herein by reference. 
     
    
     STATEMENT OF GOVERNMENT INTEREST 
       [0002]    Under paragraph 1(a) of Executive Order 10096, the conditions under which this invention was made entitle the Government of the United States, as represented by the Secretary of the Army, to the entire right, title and interest therein of any patent granted thereon by the United States. This patent and related ones are available for licensing. Contact Bea Shahin at 217 373-7234 or Phillip Stewart at 610 634-4113. 
     
    
     BACKGROUND 
       [0003]    U.S. Pat. No. 6,286,279,  Method for Attaching Fabric and Floor Covering Materials to Concrete , to Bean et al., Sep. 11, 2001, and incorporated herein by reference, teaches bonding a thin metal plate or metal foil to a concrete surface to effect a barrier to water vapor transfer. The configuration of the &#39;279 patent improves the maintenance of the bond between a concrete surface and various types of floor coverings. The &#39;279 patent teaches two systems for implementing the barrier: one uses a single-layered thin metal plate or metal foil that is folded to produce recesses much like corrugated sheet metal. One side of the foil is attached to the concrete surface using a Portland cement-based thin set grout. A second embodiment employs a two-part thin metal plate or foil. A first lower part is perforated (or slit and expanded) and attached to a second solid upper part. The lower perforated part is embedded in a layer of thin set mortar on the concrete to anchor it to the concrete. The thin set mortar that oozes through the perforations also serves as a mechanical bond, a “cementitious rivet,” supplementing the chemical bond made along the contact surface. 
         [0004]    A preferred embodiment of the present invention is an improvement on the &#39;279 patent in that it allows the thin metal plate or metal foil to be embedded just below the surface of the underlayment, concrete in the case of a “poured slab,” so that there is a layer, e.g., concrete, both above and below the thin metal plate or metal foil. That is, a robust “finish” surface, e.g., concrete, is placed above the thin metal plate or metal foil, thus presenting a durable surface of conventional appearance. One advantage of this design is the ability of the surface to resist moisture flow from without while accommodating typical use, e.g., that of hard-wheeled vehicles that would otherwise damage vinyl or carpet floor coverings. 
       SUMMARY 
       [0005]    A fluid, or vapor, barrier is encapsulated within a durable structure to preclude passage of fluid in at least one direction while retaining the durability of a surface of a structure that conventionally does not contain such a barrier. 
         [0006]    A first preferred embodiment of the present invention employs a two-part folded thin metal (or composite) plate or metal (or composite) solid (un-perforated) foil such as provided in the &#39;279 patent, but embedded just below the top surface of a durable surface such as an underlayment, typically a concrete “slab” or floor. 
         [0007]    Alternatively, a second preferred embodiment of the present invention employs a two-part thin metal plate or metal foil differing from that of the &#39;279 patent in that the second or top layer of metal is a perforated thin plate or metal foil. The perforations on the top side of the second (top) layer serve to facilitate the formation of a mechanical bond via the concrete oozing through the perforations and acting as a “cementitious rivet” between the top side of the second layer and the bottom side of the surface of the underlayment above this second (top) layer. This mechanical bond acts in addition to any chemical bond formed between the bottom side of the underlayment surface and the remainder of the upper surface of this second (top) perforated layer. This second preferred embodiment must employ a solid thin metal plate or metal foil as a first (bottom) layer to block passage of moisture through the path provided by the underlayment material, typically concrete, that, upon installation, oozed through the perforations in the second (top) layer of perforated thin metal plate or metal foil. That is, if a perforated second (top) layer of a two-part thin metal plate or metal foil is used to achieve a better bond, then the first (bottom) layer must be solid, and conversely, if a perforated first (bottom) layer is used, then the second (top) layer must be solid. 
         [0008]    Alternatively, a third preferred embodiment of the present invention employs a three-part thin metal plate or metal foil differing from that of the &#39;279 patent in that a solid center foil or thin metal plate has an expanded metal foil or thin metal plate, e.g., pleated foil, applied to both sides. Application of the top and bottom pleated foils or thin pleated metal plates may be by way of spot welding in one embodiment. This results in a three-layered system that provides opportunity for the adhesive, e.g., thin-set mortar, to infiltrate slots in the lower foil (or thin metal plate) positioned over the adhesive immediately applied to an existing slab, while the expanded foil (or thin metal plate) attached to the top of this three-layer version establishes a similar mechanical and chemical bond to the overlaid concrete that forms a surface, e.g., concrete flooring. This particular embodiment also aids in resisting “curling” of an overlaid concrete layer that provides a durable surface for use by hard-wheeled vehicles. 
         [0009]    A preferred method of applying a first preferred embodiment of the present invention to an existing porous surface, such as cured concrete, comprises:
       applying a layer of adhesive, such as thin set mortar, to the existing surface;   placing a folded or pleated thin metal plate or folded or pleated metal foil on the layer of adhesive, e.g., thin set mortar;   embedding the bottom of the thin metal plate or metal foil into the adhesive, e.g., thin set mortar;   covering the top of the folded or pleated thin metal plate or folded or pleated metal foil with a thin layer of durable material, such as concrete;   permitting the adhesive to cure; and   finishing and curing the thin layer of durable material, e.g., concrete, as needed.       
 
         [0016]    Note that if concrete is used as a finish layer, consolidation of this covering concrete must be done with care to avoid loosening the foil bonded to the adhesive, e.g., thin set mortar. 
         [0017]    As an alternative, seams between the pieces (sheets) of the folded or pleated thin metal plate or folded or pleated metal foil may be sealed with flexible commercially available room temperature vulcanizing (RTV) products appropriate for use in alkaline environments. As a further alternative, employing accordion-style pleats at edges of the thin metal plate or metal foil accommodates panel movement while avoiding tearing or breaking the folded thin metal plate or folded metal foil should the installed surface move under load. Of course, this method is not limited to existing installations but may be employed upon initial installation of an underlayment or wall. 
         [0018]    In installing a second preferred embodiment, the above method of installation may be applied using a two-part thin metal plate or metal foil having a first (bottom) layer and a second (top) layer, instead of a single folded thin metal plate or folded metal foil. 
         [0019]    In another method of installing the second preferred embodiment a two-part thin metal plate or two-part metal foil is used in which the second (top) layer incorporates perforations and the first (bottom) layer is solid. 
         [0020]    In yet another method of installing the second preferred embodiment, the immediately above method of installation may be applied using a two-part thin metal plate or two-part metal foil in which the first (bottom) layer incorporates perforations and the second (top) layer is solid. 
         [0021]    Finally, the above method of installation may be applied using the third preferred embodiment, a three-layer sandwich comprising top and bottom layers of perforated, folded or pleated foil or thin metal covering a solid middle layer of foil or thin metal. The top and bottom layers may be joined to the solid center layer by any of a number of suitable processes, e.g., tack welding. 
         [0022]    Embodiments of the present invention are not limited to underlayments but may be used on vertical or slanted surfaces where protection from fluid intrusion is desired. Further, a “one-way” vapor barrier may be installed to prevent intrusion of fluids while permitting expulsion of the same fluids or vapors. Instead of a metal foil or thin metal plate, a special “breathing” material such as those marketed under the trademark GORETEX® (liquid impermeable, moisture vapor transmissive material) may be used in place of metal. This would have particular application in below grade applications such as basement floors or walls and in environments of high humidity such as kitchens or bathroom floors or walls that otherwise “sweat.” In addition to embedding the GORETEX® (liquid impermeable, moisture vapor transmissive material) lining in concrete on a slab, it could be embedded just beneath a porous outer stucco or similar coating to achieve the same effect as the metal barrier does in the underlayment while also permitting “out gassing” of vapors from within the room. 
         [0023]    Embodiments of the present invention may be used in any application where it is necessary to prevent the movement of fluids (liquid or gas) through porous material, such as concrete. Specifically, embodiments may be used to block the movement of water vapor and will be equally effective in preventing the movement of stable gases, such as radon, through porous material, such as concrete. 
         [0024]    The “embedded barrier” of the present invention, in all of its preferred embodiments, is unique in its implementation. For example, conventionally, a concrete slab has been “sealed” by pre-placing a polymer membrane under the slab prior to placing the new concrete. Once the concrete slab had been installed, the slab could be further sealed only at its top surface. This sealing of the top surface has been accomplished conventionally by using epoxy, fiberglass or combinations of fiberglass and epoxy, leaving a surface that was less durable than a concrete surface. 
         [0025]    To summarize some of the salient advantages of preferred embodiments of the present invention:
       it permits modifying existing installations, e.g., addition of concrete above the metal barrier on existing slabs;   it allows a trafficked surface above a vapor barrier to be made of durable castable material such as concrete or asphalt concrete;   it provides a continuous sheet of metal foil that also serves to reinforce an underlayment, such as a concrete slab;   it reduces the opportunity for cracking that occurs on one side of a structure to propagate to the other side;   it reduces the opportunity for fractures that exist in the lower part of an underlayment, e.g., a concrete slab, to widen or propagate laterally;   in a preferred embodiment it prevents curling of a top surface of concrete that has been applied to an existing concrete slab; and   in an alternative embodiment, it accommodates joints between panels of structure, such as an underlayment, by employing a pleated barrier joining section thus permitting movement without compromising the integrity of the barrier.       
 
         [0033]    Further advantages of the present invention will be apparent from the description below with reference to the accompanying drawings, in which like numbers indicate like elements. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0034]      FIG. 1  is a top view of a single piece thin metal plate or metal foil that may be used in a preferred embodiment of the present invention. 
           [0035]      FIG. 2A  is a top view of the perforated piece of a two-piece thin metal plate or metal foil used in a preferred embodiment of the present invention. 
           [0036]      FIG. 2B  is a top view of the solid piece of a two-piece thin metal plate or metal foil used in a preferred embodiment of the present invention. 
           [0037]      FIG. 3A  is a perspective view of the single piece thin metal plate or metal foil of  FIG. 1  as installed in a typical installation. 
           [0038]      FIG. 3B  is a perspective view of the two-piece thin metal plate or metal foil of  FIGS. 2A and 2B  as installed in a typical installation. 
           [0039]      FIG. 4  depicts an alternative installation of a preferred embodiment of the present invention in which an expansion joint is used between flooring panels. 
           [0040]      FIG. 5  depicts an alternative installation of a preferred embodiment of the present invention in which an expansion joint is used between a flooring panel and an adjoining vertical wall. 
           [0041]      FIG. 6A  depicts a single layer thin metal plate or foil that has been pleated to be used with a preferred embodiment of the present invention. 
           [0042]      FIG. 6B  depicts a three-layer barrier, two of which layers are that configuration shown in  FIG. 6A  as may be used with a preferred embodiment of the present invention. 
           [0043]      FIG. 7  depicts an alternative means of joining two sections of barrier that may be used in a preferred embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION  
       [0044]    Refer to  FIGS. 1 ,  3 A,  3 B, and  6 A. Provided is a configuration creating a fluid barrier within porous material such as concrete. In a preferred embodiment, a barrier panel  100 , in one embodiment including pleats  101  and having pleated edges  102 , is placed between a “base”  311  of porous material, such as a concrete slab, and an emplaced topmost section  313  of durable material, such as concrete, thus creating a topmost surface suitable for use by wheeled traffic. A single layer  600  plate or foil with pleats  101  and related spacings  601  between the pleats  101  may be used as an embedded fluid barrier such as shown at  310 . Also shown at  310  are depictions  315  of the adhesive  312  as it forms in the valleys between pleats  101  and the formation of anchoring portions  314  of the initially “flowable” top layer  313  as it is placed on the surface  103  of a pleated single layer panel  100  of the configuration at  310 . 
         [0045]    Refer to  FIGS. 3A ,  3 B and  7 . Also provided in a preferred embodiment of the present invention is a configuration  310  such as shown in  FIG. 3A  or the configuration  320  shown in  FIG. 3B  implementing a barrier to fluid flow in at least one direction and enclosed within porous material. Either configuration  310 ,  320  uses a durable top section  313  applied over the barrier panel  100  placed upon adhesive  312  coated on a first section  311  of the porous material. Either configuration  310 ,  320  is thus made suitable for routine use by wheeled traffic. Both configurations  310 ,  320  comprise:
       at least one layer of adhesive  312  applied to a top surface of the porous material comprising a base  311 , e.g., thin set mortar applied to a concrete slab;   panels  100  of non-porous material having edges  102  suitable for overlapping, e.g., pleated edges, as shown at  701  of  FIG. 7 , affixed to a topmost layer of adhesive  312  so as to completely cover the adhesive  312 , a flexible sealant as shown at  702  of  FIG. 7  applied between the overlapping edges as shown at  701  of  FIG. 7 ; and   the topmost section  313  emplaced upon the panels  100  so as to completely cover all said panels  100 , the topmost section  313  incorporating the top surface suitable for routine use by wheeled traffic.       
 
         [0049]    In a preferred embodiment of the configuration, the barrier is a vapor barrier embedded, i.e., completely enclosed, in porous material. The non-porous material used for the panels  100  may be selected from: a metal, a metal alloy, a steel alloy, a stainless steel, a composite material, a composite material containing at least some metal, and combinations thereof. 
         [0050]    In a preferred embodiment of the configuration, the non-porous material comprises at least one metal and the porous material comprises at least some concrete. Further, the adhesive  312  may be a thin set mortar applied to a thickness of about 6 mm (¼ inch). In a preferred embodiment of the configuration in which the porous material at least partially comprises concrete, the topmost section may comprise concrete applied to a thickness of about 2.5 cm (1 inch) or more. 
         [0051]    Refer to  FIG. 7 . In a preferred embodiment of the configuration, a seal  702  comprises a continuous bead of a flexible sealant applied along the entire length between all overlapped edges  701  of the panels  100 . A preferred embodiment of flexible sealant is a RTV sealant. 
         [0052]    Refer to  FIGS. 2A ,  2 B, and  3 B. In a preferred embodiment of the configuration, the panels  100  are plates of a total thickness less than about 6 mm (¼ inch). In an alternate preferred embodiment, the panel  100  comprises a first perforated plate  210  in contact with a second solid plate  220 , i.e., a two-layer panel  100 , each of the first  210  and second  220  plates being of a total thickness of less than about 3 mm (⅛ inch). A preferred configuration places a first perforated plate  210  “layer” immediately adjacent the bottom side of the topmost section  313 , e.g., the finish layer of concrete. A generic two-layer configuration  321 ,  322  representing this preferred configuration is shown in  FIG. 3B . The first perforated plate  210  would be placed at  321  in  FIG. 3B  and the second solid plate  220  at  322  in  FIG. 3B . 
         [0053]    Refer to  FIGS. 2A ,  2 B, and  3 B. In an alternate preferred embodiment of the configuration, the panels  100  comprise a multi-layer foil of a thickness less than about 2 mm (0.008 inch) and preferably in the range of about 0.5-1.5 mm (20-60 mils), and may be represented as in  FIG. 3B  as a perforated foil (such as depicted in  FIG. 2A  at  210 ) at  321  and a solid foil (such as depicted in  FIG. 2B  at  220 ) at  322 . Each of the foil layers  210 ,  220  in a two-layer foil  321 ,  322  used in a preferred embodiment of the present invention has a total thickness of less than about 1 mm (0.04 inch) and preferably in the range of about 0.25-0.76 mm (10-30 mils). 
         [0054]    Refer to  FIGS. 1 ,  3 A,  6 A and  6 B. In yet another preferred embodiment, the configuration employs panels  100  comprising three-layers, two identical configurations as shown at  600 , and a single flat configuration as shown at  610 . In  FIG. 6A , the adhesive  602  is shown as it oozes into the folds of the foil or thin metal from the layers of porous material (not shown separately in  FIG. 6A ) above and below the foil or thin metal configuration  600 . In  FIG. 6B , by contrast, the adhesive  620  is emplaced to adhere to the portion of the thin foil or thin metal configuration  600  in direct contact with a separate middle layer  610  as described immediately below. These configurations  600 ,  610  may be metal (or composite) foil or thin metal (or composite) sheets or plates. The top  600  and bottom  600  layers of the three-layer panel  600 ,  610  may be perforated, a solid that is folded or pleated, and combinations thereof, while the middle layer  610  must be solid if both the top and bottom layers  600  are perforated. As foils, the layers  600 ,  610  each may be of a thickness less than 1.0 mm (40 mils) and more preferably less than about 0.76 mm (30 mils) and most preferably in a range of thickness from about 0.25-0.76 mm (10-30 mils). 
         [0055]    A preferred method of implementing an embedded barrier comprises:
       applying at least one layer  312  of adhesive, such as a thin set mortar, to an entire first surface of the porous material of the base  311 , e.g., a concrete slab, prior to emplacing the topmost section  313 , e.g., a finish layer of concrete;   placing panels  100  of non-porous material, such as a metal or composite plate or metal or composite foil, upon a topmost layer  312  of adhesive (if more than one layer of adhesive is used), overlapping edges  102  of each panel  100  with edges of any panels  100  placed adjacent thereto in the same plane along the topmost layer  312  of adhesive such as shown at  701  in  FIG. 7 , and completely covering the topmost adhesive layer  312  with the overlapping panels  100 ;   establishing a seal  702  as shown in  FIG. 7  between all the overlapped panel edges  701 ; and   emplacing at least one layer of material comprising a topmost section  313  upon the panels  100  such that each panel  100  is confined below the topmost section  313  and above a topmost layer  312  of adhesive.       
 
         [0060]    Employing this method, i.e., providing one or more adhesive layers  312  upon a surface of a base  311  of porous material, placing “barrier” panels  100  of one or more layers such as layers depicted at  210 ,  220 ,  600 ,  610  upon the topmost layer  312  of adhesive, establishing a seal  702  between the overlapped edges  701  of the panels  100  and emplacing a topmost section  313  to encapsulate the panels  100 , implements a fluid barrier within porous material, preferably durable porous material such as concrete. 
         [0061]    Refer to  FIG. 3A . In one preferred method, the adhesive  312  may then be allowed to “set” or cure prior to installing a finish layer  313  over the plate (or foil)  100 . Not all methods may require curing of the adhesive  312  prior to the finish step, however. The finish layer  313  may be a poured fluid, such as concrete, such that the concrete oozes into the spaces between the channels  101  as shown at  314 , thus facilitating a strong bond between the plate (or foil)  100  and the finish layer  313 . For those underlayments  311  that are exposed to heavy traffic, including hard-wheeled vehicles, for example, the finish layer  313  may be relatively thick concrete. In one preferred embodiment, the result is a multi-layered configuration  310  that achieves an effective moisture and vapor barrier to fluid ingress from beneath the underlayment  311 , while permitting heavy traffic on its concrete finished surface  313 . 
         [0062]    The method of emplacing a fluid barrier within porous material extends to establishing a vapor barrier in porous material. The vapor barrier may be a one-way barrier such that the configuration is permitted to “breathe” or “outgas” in one direction while establishing and maintaining a fluid barrier in the opposite direction. 
         [0063]    In a preferred embodiment of a method of implementation of the present invention, the method employs non-porous material comprising at least one metal and the porous material comprises at least some concrete. Further, the topmost adhesive layer  312  may be a thin set mortar applied to a thickness of about 6 mm (0.25 inch). In a preferred embodiment in which the porous material at least partially comprises concrete, the topmost section may comprise concrete applied to a thickness of about 2.5 cm (1.0 inch) or more. 
         [0064]    Refer to  FIGS. 3A ,  3 B, and  7 . In a preferred embodiment of the present invention, a seal  702  may be established, at least in part, by applying a continuous bead of a flexible sealant along the entire length between all overlapped edges  701  of the panels  100 . A preferred embodiment of flexible sealant is a RTV sealant. In applications where concrete is to be applied as a finishing layer  313 , the RTV sealant should be suitable for use in alkaline environments. 
         [0065]    Refer to  FIGS. 1 ,  2 A,  2 B and  3 B. In a preferred configuration of the present invention, the panels  100  comprise multiple layers  321 ,  322  of plates of a total thickness less than about 6 mm (0.25 inch). In an alternate configuration, the panels  100  comprise a perforated plate  210  as a first layer  321 , the perforated plate  210  having evenly spaced perforations  212  on its interior surface  211  and abutted about its entire surface area to a second solid plate  220  as a second layer  322 , the solid plate having a solid interior surface  221 , and each of the first  210  and second  220  plates being of a total thickness of less than about 3 mm (0.125 inch). A preferred method is to place the first perforated plate  220  immediately adjacent the bottom side of the topmost section  313  as shown at  321  in the configuration  320  of  FIG. 3B . 
         [0066]    Refer to  FIGS. 2A ,  2 B, and  3 B. An alternate preferred configuration employs panels  100  comprising multi-layer foil of a thickness less than about 4 mm (0.16 inch), and more preferably less than about 2.5 mm (100 mils), and most preferably about 0.5 mm to 1.5 mm (20-60 mils). 
         [0067]    In yet another alternate preferred configuration, the panels  100  comprise a first perforated foil  210  as a first layer  321  of a two-layer foil  321 ,  322 , the second layer  322  being a solid foil  220 . Each of the first and second foil layers  321 ,  322  has a total thickness of less than about 2 mm (80 mils), and more preferably less than about 0.76 mm (30 mils), and most preferably about 0.25 mm to 0.76 mm (10-30 mils). In a preferred embodiment, the first perforated foil  210  is placed immediately adjacent the bottom side of the topmost section  313  as shown at  321 . 
         [0068]    Refer to  FIGS. 1 ,  3 A,  6 A and  6 B. In yet another preferred embodiment, the configuration employs panels  100  comprising three-layers, two identical configurations as shown at  600 , and a single flat configuration as shown at  610 . These may be metal (or composite) foil or thin metal (or composite) sheets or plates. The three layers  600 ,  610  are bonded together by any of a number of suitable means, such as by gluing, heating, applying pressure, soldering, tack welding, or combinations of the above. The top  600  and bottom  600  layers of the three-layer panel  600 ,  610  may be perforated, a solid that is folded or pleated, and combinations thereof, while the middle layer  610  must be solid if both the top and bottom layers  600  are perforated. As foils, the layers  600 ,  610  each may be provided in a thickness less than 1.0 mm (40 mils) and more preferably less than about 0.76 mm (30 mils) and most preferably in a range in thickness from about 0.25-0.76 mm (10-30 mils). 
         [0069]    Refer to  FIG. 4 . Some installations  400  of underlayments  311 , such as a concrete slab, applied over a prepared base  404 , such as an aggregate, incorporate embedded expansion joints. A preferred embodiment of the present invention incorporates a sealed expansion joint  401  between each of the overlaid top sections  313  and a corresponding portion of the underlayment  311 . This sealed expansion joint  401  comprises a pleated non-porous strip  402  that is placed over the adhesive  312  at the expansion joint  401  to overlap the entire length of each side of the expansion joint  401  below the installed panels  100  (that may be thin metal or composite plates or foil layers), each overlap of a width less than about 5.0 cm (2.0 inches). The strip  402  is then sealed with an appropriate sealant as shown at  403  along each longitudinal edge of the strip  402  between the top surface of the edge of the strip  402  and the bottom of each panel  100  abutting the expansion joint  401 . A preferred embodiment employs a continuous bead  403  of flexible sealant, such as an RTV, applied along the entire length of the expansion joint  401 . 
         [0070]    Refer to  FIGS. 2A ,  2 B and  3 B.  FIG. 2A  depicts the perforated piece  210  of a two-piece thin metal plate (or foil) structure shown installed in  FIG. 3B  at  321 ,  322 . The perforations  212  in the main part  211  of this perforated piece  210  facilitate bonding of the metal plate (or foil) structure to either the adhesive layer  312  or the overlaying finish layer  313  as shown in the resultant multi-layered structure  320  of  FIG. 3B . The solid piece  220  of the two-piece thin metal plate (or foil) is shown installed as one of the layers in  FIG. 3B  at  321 ,  322 . The configuration  320  of  FIG. 3B  facilitates additional mechanical bonding of the two-piece plate  321 ,  322 , to either the adhesive layer  312  or the finish layer  313 , but not both, while providing a solid interface to prevent moisture or vapor flow from beneath the underlayment  311 . A preferred method of installation is to mount the perforated piece  210  against the finish layer  313  and the solid piece  220  against the adhesive layer  312 . In the case of a concrete finish layer  313 , this provides protection for the mechanical bond developed by the concrete as it oozes into the perforations  212  in the perforated piece  210  since no moisture or vapor passes through the solid piece  220  mounted next to the adhesive layer  312 , for example, thin set mortar in the case of a concrete underlayment  311 . Although the perforations  212  are shown as circular holes in  FIG. 2A , other means of perforation may be used. For example, the perforated piece  210  may comprise metal screen material very similar to that used in screening windows to prevent insect ingress, a wire mesh, or combinations of types of perforations. Also shown in  FIGS. 2A and 2B  are alternative edges  102  that facilitate flexion of the installed two-piece plate (or foil)  210 ,  220  in much the same manner as described above for the one-piece configuration  100  of  FIG. 1 . The two pieces  210 ,  220  may be joined together prior to installation by any of a number of means such as application of adhesive to parts of their adjoining surfaces, mechanically pressing edges together, soldering, welding, and combinations of these means. Further, the two pieces  210 ,  220  may be installed separately and either joined as would be done in methods described above for joining prior to installation or simply placed one above the other as part of the installation with the weight of the finish layer  313  and the adhesion of the adhesive layer  312  serving to maintain proper alignment. Adjacent two-piece plates (or foils)  210 ,  220  may be connected in the same manner as for the one-piece plates (or foils)  100  as described above. 
         [0071]    Refer to  FIG. 4 . Expansion joints  401  provide for movement of underlayment  311  in many cases. A preferred embodiment  400  of the present invention provides for bridging these joints  401  while sealing the joint  401  from moisture or vapor and avoiding tearing the underlying metal plate (or foil)  100 ,  210 ,  220 ,  321 ,  322 . In a preferred embodiment of the present invention, a separate flexible and expandable “bridge”  402  is provided for bridging expansion joints in underlayments  311  above a sub-grade  404 . This bridge  402  may be a long narrow section of thin metal plate (or foil) similar to that used as the moisture and vapor barrier. The longitudinal edges are flat while the center section is accordion-shaped or pleated to permit movement. These bridges  402  are installed over, and bond to, the adhesive layer  312  at the expansion joint  401  prior to installation of the thin metal plate (or foil)  100 ,  210 ,  220 ,  321 ,  322 . The bridges  402  are then bonded to the thin metal plate (or foil)  100 ,  210 ,  220 ,  321 ,  322  via any of a number of suitable means such as the application of a continuous bead  403  of a flexible sealant, e.g., any of various commercial RTV sealants suited to the application. 
         [0072]    Refer to  FIG. 5 . In much the same way as expansion joints  401  are provided for in underlayments  311 , the joint  501  between a floor and a wall  504  is also subject to movement and a preferred embodiment  500  of the present invention provides for addressing this joint  501  also. The bridge  502  used in this application is affixed at one end to the underlayment in the same manner as for the in-floor expansion joint  401 . The bridge  502  is bent at a right angle to permit installation along the adjoining wall  504  to a point just above the top of the finish layer  313 . A bead  503  of suitable flexible sealant, such as any of a number of commercial RTV sealants, is applied along the entire length of the bridge  502  at the wall  504 . 
         [0073]    The abstract of the disclosure is provided to comply with the rules requiring an abstract that will allow a searcher to quickly ascertain the subject matter of the technical disclosure of any patent issued from this disclosure. 37 CFR § 1.72(b). Any advantages and benefits described may not apply to all embodiments of the invention. 
         [0074]    While the invention has been described in terms of its preferred embodiments, those skilled in the art will recognize that the invention can be practiced with modifications within the spirit and scope of the appended claims. For example, although the configuration is described in specific examples related to concrete structure, it may be adapted to other porous construction materials, such as drywall, chipboard, wood, tile, composites, and combinations thereof. Thus, it is intended that all matter contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative rather than limiting, and the invention should be defined only in accordance with the following claims and their equivalents.