Multiple sheet building wrap for use in external wall assemblies having wet-applied facades

Abstract: A multiple sheet building wrap for wrapping the structural components of a building in order to protect the underlying structural components and optional building sheathing from moisture is provided. The building wrap is particularly useful under facades such as wet applied stucco or engineered stone, demonstrating good drainage of liquid water and moisture vapor permeability. The building wrap is a composite of a water resistive barrier, a three-dimensional mesh layer and a porous intervening layer which acts to filter the stucco as it is applied. An exterior wall construction incorporating such building wrap is also provided. (end of abstract)

Multiple sheet building wrap for use in external wall assemblies having wet-applied facades description/claims

Brief Patent Description

Full Patent Description

Patent Application Claims

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a building wrap for wrapping the structural components of a building in order to protect the structural components and optional building sheathing from moisture.

2. Description of the Related Art

Two sheets of a water resistive barrier (“WRB,” also commonly referred to as “weather-resistive barrier” or “house wrap”) material are known for use as a building wrap under facade materials such as three-coat stucco or traditional Portland cement which are applied wet, e.g., using a trowel or by spraying. For instance, such building wraps can include two layers of Grade D building paper, two layers of asphalt-saturated kraft paper, two layers of building felt, two layers of a conventional polymeric house wrap, or one layer of building paper combined with one layer of polymeric house wrap. Known polymeric house wraps for use as WRBs include, for example, spunbond polyethylene sheet available under the trade name Tyvek® from E. I. du Pont de Nemours & Co., Wilmington, Del. (“DuPont”); polyolefin nonwoven sheet available under the trade name Styrofoam™ Weathermate™ Plus from The Dow Chemical Company, Midland, Mich.; spunbonded polypropylene-microporous film laminate available under the trade name Typar® Weather Protection Membrane from Fiberweb, London, UK; woven polypropylene sheet with a perforated coating available under the trade name Pinkwrap® from Owens Corning, Corning, N.Y.; and coated nonwoven sheet available under the trade name WeatherSmart™ from Fortifiber Building Systems Group, Reno, Nev. The space between the two layers provides a drainage space for any liquid water that penetrates the outer layer.

Also known is the use of a layer of water resistive barrier combined with a layer of a three-dimensional mesh through which water may drain. The mesh layer of these systems allows the wet-applied stucco to penetrate the mesh, thereby interfering with the drainage of liquid water through the mesh and inhibiting the transport of moisture vapor through the water resistive barrier.

Currently, the International Building Code®, published by International Code Council, requires the use of “weather-resistant barriers” behind stucco facades as follows:

- 2510.6 Weather-resistant barriers. Weather-resistant barriers shall be installed as required in Section 1404.2 and, where applied over wood-based sheathing, shall include a weather-resistant vapor-permeable barrier with a performance at least equivalent to two layers of Grade D paper.
- Exception: Where the weather resistant barrier that is applied over wood-based sheathing has a water resistance equal to or greater than that of 60 minute Grade D paper and is separated from the stucco by an intervening, substantially non-water-absorbing layer or drainage space.

It would be desirable to have an alternative multiple sheet building wrap available for use under wet-applied stucco that would retain good drainage of liquid water, moisture vapor permeability and that would protect the underlying building structure from the penetration of liquid water, and an economical process for installing such a building wrap.

BRIEF SUMMARY OF THE INVENTION

The present invention is directed to a multiple sheet building wrap for wrapping the structural components and optional sheathing of a building in order to protect the structural components and optional sheathing from moisture, the sheet comprising:

- a. a moisture vapor permeable water-resistive barrier selected from the group consisting of asphalt-saturated papers, felts, woven fabrics, flash-spun plexifilamentary sheets, spunbond nonwoven sheets, spunbond-meltblown nonwoven sheets, spunbond-meltblown-spunbond nonwoven sheets, microperforated coated sheets comprising woven tapes, laminates thereof, and laminates comprising a nonwoven or woven fabric and a porous moisture vapor permeable film;