Construction membrane

Details Construction membrane Construction membrane

1999-06-09

2002-03-12

Copenheaver, Blaine (Department: 1772)

Stock material or miscellaneous articles

Structurally defined web or sheet

Nonplanar uniform thickness material

C428S182000, C428S219000, C428S913000, C052S169140, C052S408000, C052S630000

Reexamination Certificate

active

06355333

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to air and water infiltration barrier sheet materials useful in the construction of housing and other structures. More particularly, the invention relates to a sheet material that is permeable to moisture vapor, but is substantially impermeable to liquids and air, and that provides channels for drainage of liquids when the sheet material is incorporated in a wall construction. The invention further relates to wall constructions made with such sheet material, including stucco-faced wall constructions, brick-faced and stone-faced wall constructions, and wood and vinyl siding wall constructions.
BACKGROUND OF THE INVENTION
A number of different air and/or water infiltration barrier materials are currently used in the construction of the external walls of structures. Barrier materials are available in the form of sheets that can be incorporated into the walls of a structure under the outer facade of the wall. Such barrier sheet materials are designed to prevent the intrusion of incidental water, which passes through the primary facade, into the frame of the structure where water could cause mold, mildew, rotting, or other structural damage. Some barrier sheet materials also prevent the infiltration of air (and the moisture carried with such air) into the structure so as to make the structure more comfortable and energy efficient. While barrier sheet materials should be substantially impermeable to liquid water and air, they should not trap moisture vapor within walls where the vapor could condense as water and cause mildew or structural damage. It is also important that a barrier sheet material not trap water that enters walls through exterior cracks, around windows, doors and other joints, or around water taps or electric fixtures.
Barrier sheet material has been used in most kinds of exterior wall constructions including wall constructions with stucco, brick, stone, and siding facades. Barrier sheet materials used under siding include asphalt impregnated kraft papers and felts, perforated polymer films, spunbonded polymer sheets, and microporous film laminates. Barrier sheet materials that have been used under stucco include asphalt impregnated kraft papers and felts, spunbonded polymer sheets, and perforated polymer films.
One barrier sheet material that has been advantageously used in both siding and stucco wall constructions is TYVEK®) spunbonded polyethylene sheet sold by E.I. duPont de Nemours & Company of Wilmington, Del. (“DuPont”). Tyvek® is a registered trademark of DuPont. TYVEK® spunbonded polyethylene sheet is made from a consolidated web of flash-spun polyethylene plexifilamentary film-fibrils made as disclosed in U.S. Pat. No. 3,169,899 to Steuber and bonded as disclosed in U.S. Pat. No. 3,532,589 to David or PCT Publication No. WO 97/40224 (all assigned to DuPont). As used herein, the term “plexifilamentary” means a three-dimensional integral network of a multitude of thin, ribbon-like, film-fibril elements of random length and with a mean film thickness of less than about 10 microns and a median fibril width of less than about 25 microns. In plexifilamentary structures, the film-fibril elements are generally coextensively aligned with the longitudinal axis of the plexifilamentary structure and they intermittently unite and separate at irregular intervals in various places throughout the length, width and thickness of the plexifilamentary structure to form a continuous three-dimensional network. A TYVEK® spunbonded polyethylene sheet designed for use as a barrier sheet material for construction applications has been sold by DuPont under the names TYVEK® Housewrap and TYVEK® HOMEWRAP®.
In structures made using frame construction, the frame of the structure is generally made from metal or wood studs covered with an exterior sheathing such as plywood, oriented strand board (“OSB”), composite particle board, gypsum board, or foam board. This exterior sheathing is covered with a barrier sheet material, which is then covered with an exterior facade material such as wood siding, hardboard or vinyl siding, brick or stone, or stucco. In some cases, the barrier sheet material is applied directly to the frame studs without an exterior sheathing (“open frame construction”).
Siding is generally applied directly over the barrier sheet material by pounding nails through the siding, the barrier sheet material, and into the sheathing or the studs. The nail holes through the barrier sheet material can provide an avenue through which air, moisture vapor, or water can get through the barrier sheet material. Water intrusion behind barrier sheet material applied under siding can also occur around windows, doors, and electrical fixtures that have been poorly flashed or caulked, or at other joints and penetrations. If water finds its way behind the barrier sheet material, whether through nail holes or through poorly sealed joints, this bulk water can build up behind the barrier sheet where the water is likely to damage the structure's sheathing, insulation or frame.
Where a barrier sheet material is used in frame construction faced with brick or stone, water can find its way into walls through cracks and pores in the pointing, the brick, or the stone. Water incursion through the brick or stone facade is most likely to occur around windows, doors, and electrical fixtures, and along the roof line, especially if joints have been improperly flashed or caulked. Water that penetrates the exterior facade can then penetrate the barrier sheet material if it is difficult for the water to drain down the exterior side of the barrier sheet. Water that finds its way behind barrier sheet material applied under brick or stone may damage the structure's sheathing, insulation or frame.
In frame construction faced with traditional three coat Portland cement plaster, known as stucco, the barrier sheet material is incorporated into the stucco-faced wall construction
10
, as shown in FIG.
1
. In the stucco-faced wall construction
10
, the studs
12
of the structure are covered with either line wires
14
(open frame construction) or with one of the sheathing materials (not shown) discussed above. The wires
14
or the sheathing are covered with a barrier sheet
16
. In stucco-faced wall constructions, the barrier sheet materials that have traditionally been used are asphalt impregnated rag felts and water resistant papers such as asphalt saturated kraft paper. Another barrier sheet that has more recently been used in stucco-faced frame construction is TYVEK® spunbonded polyethylene sheet. The barrier sheet material can be stapled, nailed or glued to the studs or sheathing material. A metal lath
18
, such as a self-furred hexagonal woven wire lath (“chicken wire”), is applied over the barrier sheet
16
and attached to the studs
12
and/or the sheathing with staples or furring nails (not shown). A scratch coat
22
of stucco is applied over the wire lath
18
so that the stucco passes through the lath and contacts the barrier sheet. After the scratch coat has had an opportunity to dry, an intermediate brown coat
24
of stucco is applied over the scratch coat
22
. Once the brown coat has had an opportunity to dry, a finish coat
26
of stucco is applied over the brown coat
24
. Finish coat
26
may be pigmented or the finish coat may be painted.
Cracking of stucco frequently occurs while the stucco is drying and curing, or during subsequent thermal expansion and contraction of the sheathing, wood studs, or stucco. Water can pass through cracks in the stucco, through improperly sealed joints, or even through the porous stucco itself. Water that finds its way between the stucco and the barrier sheet, and water absorbed into an absorbent barrier sheet material (such as kraft paper), can generate additional breakdown of the stucco. Water passing through an absorbent barrier material can wet wooden studs so as to cause crack inducing expansion and contraction of the wall. Water absorbed into the barrier material and water present on the front or back

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