Note: Descriptions are shown in the official language in which they were submitted.
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SELF-VENTING MOISTURE BARRIER AND BREATHER MEMBRANE
FOR EXTERIOR WALL SYSTEMS
FIELD OF INVENTION
This invention relates to a corrugated, self venting moisture barrier and
breather membrane for exterior wall systems of a building.
BACKGROUND OF THE INVENTION
Water-resistant breather membranes commonly known as building
papers, or more recently as house-wraps, have been a component within wall
assemblies for many decades. The typical house wall assembly consists of wood
(or
metal) studs, fastened to top and bottom plates which are themselves fastened
to other
framing units such as a floor assembly and a roof assembly. On the inside wall
surface, a sheet material such as gypsum board is commonly fastened with nails
or
screws to the wall studs and beneath this finish a vapour barrier sheet, such
as
polyethylene, is placed. The space between studs is filled with insulation and
a rigid
sheathing material such as plywood, Oriented Strand Board (OSB) or shiplap
lumber
is usually fastened to the outer face of the studs. The above assembly forms
the
structural and thermal protective portions of a typical outside wall. As a
final
finishing, the weather protective components are installed, consisting of a
layer of
breathable, water-resistant sheathing membrane and then a layer of cladding.
The layer of breather membrane, commonly referred to as building
paper, is intended to function as a barrier against entry of wind-driven or
otherwise
motivated moisture which bypasses or penetrates the outer cladding. In
addition to
preventing the entry of outside moisture into the wall assembly, the breather
membrane must allow the release of water vapour from within the wall to
prevent
accumulation and condensation- of water within the wall. In this regard it
must be a
"breather" for water vapour.
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In recent years many problems have been encountered with the above
described wall assemblies in wet coastal climates. The problems generally
involve
the inability of the wall assembly to dry itself adequately between periods of
rain
induced wetting, leading to fungus growth, deterioration of the wood sheathing
and
rotting of structural members.
For the purpose of energy conservation, building codes have required
builders to install more insulation into walls, thus preventing inside source
heat from
aiding in wall drying, and also to install better, more effective vapour
barriers which,
however, also function as air barriers. These measures prevent air passage
through
the wall assembly and eliminate a further drying mechanism (namely, air
movement).
As a result all drying outside the insulation can only take place to the
exterior without
the aid of air movement. Further, if the cladding is placed tightly against
the wall
sheathing it too restricts the release of water vapour out of the wall.
However, if the cladding is spaced away from the wall sheathing
allowing entry of air to provide ventilation between sheathing and the
cladding, it
greatly improves the walls' drying ability. A further benefit of having a
space
between cladding and sheathing is to help prevent moisture ingress from the
cladding
by capillary forces. Spacing of cladding away from the wall can be achieved
using
various types of furring materials such as wood strapping, etc. This method
can be
laborious and costly.
However, by using a breather membrane manufactured as a corrugated
sheet having evenly spaced ridges, or corrugations, the corrugations perform
the
function of furring materials by spacing the cladding away from the wall
sheathing.
The corrugations permit entry of ventilating air behind the cladding and also
permit
easy drainage of any errant moisture which bypasses the cladding.
A number of patents disclose moisture and vapour barriers for
buildings, but none with a portion that is corrugated or that otherwise
provides a
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convenient means for physically separating the exterior cladding from the wall
sheathing for the purposes of preventing moisture ingress by capillary action
from
moist cladding, allowing entry of air between the wall sheathing and the
cladding to
assist in drying, and allowing downward flow of errant moisture between the
wall
sheathing and the cladding.
United States Patent No. 4,866,897 (Yount) describes a reinforced
composite sheathing paper for use in wall construction between interior
framing and
exterior materials such as stucco, to provide a single strengthened sheet
against which
stucco can be applied. No layer of the sheathing paper is corrugated, and the
sheathing paper lacks the advantages of a vertically corrugated moisture
barrier.
United States Patent No. 5,027,572 (Purcell et al.) discloses a wall
system, wherein a moisture and vapour barrier is positioned directly between
the
substrate and insulation layers of an exterior insulation finish system to
provide
thermal stability regardless of climatic variations. This moisture and vapour
barrier
comprises a two-part membrane of multiple cross-laminated layers of
polyethylene
film fully bonded to a layer of rubberized asphalt. None of the layers of the
moisture
and vapour barrier are corrugated, nor does Purcell et al. disclose any other
means
whereby the exterior wall cladding is physically separated from the sheathing.
Purcell et al. makes no attempt to permit air movement between the cladding
and the
wall sheathing to assist in the drying process, but, quite the opposite,
specifically
aims to add to the insulation value of the overall system by eliminating all
air
movement in the form of draft.
United States Patent No. 4,543,158 (Bonduc et al.) describes an
asphalt-saturated sheet-type felt material used as siding or roofing
underlayment. No
part of this underlayment is corrugated.
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SUMMARY OF THE INVENTION
The problems of the prior art have been overcome by this invention
which provides a corrugated self-venting moisture barrier and breather
membrane in
an exterior wall system. Specifically, this invention combines a number of new
functions beneath cladding: air ventilation, furring, and a moisture barrier
with a
mufti-layer corrugated, breather-type, asphalt-saturated building paper.
Corrugated
paper in general and asphalt-laminated building paper are well known. However,
the
corrugated product of this invention consists of laminating a layer of non-
corrugated,
asphalt-saturated breather paper to a layer of corrugated asphalt-saturated
breather
paper. The laminating is accomplished by applying intermittent strips of
adhesive to
the non-corrugated sheet just before it meets and joins up with the corrugated
sheet.
The finished product is then wound into rolls of convenient size. In a wall
assembly
the laminate is positioned between the outside of the sheathing and the
external finish
or cladding.
The corrugated building paper of this invention provides vertical
channels for moisture drainage and for air movement beneath the external
cladding.
The vertical drainage channels are provided by the space between the
corrugated layer
and the non-corrugated layer of the laminate. The vertical air channels are
provided
by the space between the corrugated layer of the laminate and the sheathing or
cladding of the exterior wall system. In each case, the corrugations are rigid
enough
to resist crushing when cladding is applied.
Another embodiment of the product consists of a layer of non-
corrugated, preferably non-coated, porous fibreglass mat laminated to the
corrugated
asphalt-saturated breather paper. The porous fibreglass mat functions as a
backing
sheet behind plaster or stucco-cement to prevent the plaster or stucco from
filling the
corrugation channels but it permits moisture to enter the drainage channels.
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The proper placement of the self-venting moisture barrier and breather
membrane in exterior wall systems is essential. It is typically held in place
in a wall
structure by fastening it to the outer sheathing beneath the exterior cladding
which
may, for example, be wood siding, plastic (vinyl) siding,, stucco, synthetic
stucco, an
exterior insulation finish system (E.I.F.S.), or the like. The corrugated
sheets are
installed horizontally preferably with the corrugated side facing out for use
with solid
cladding. For stucco cladding however, the corrugated sheet is preferably
placed
with corrugations facing in towards the wall cavity and the fibreglass mat
facing
outward so as to prevent intrusion of stucco into the corrugation channels.
The sheets
are positioned so that horizontal laps are shingle-style and the corrugated
channels are
vertically aligned. All moisture which bypasses the cladding should preferably
have
ready access to the vertical channels for unrestricted drainage. Each sheet
must direct
this moisture onto the sheet below it and thence to exit the wall assembly at
the
bottom by way of properly positioned metal flashing. Allowances are made for
air
entry at the bottom of a wall assembly and the air channels may be open to the
attic
or soffit space.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a perspective sectional view of the moisture barrier and
breather membrane according to the present invention, showing its layers.
Figure 2 is a perspective view of an embodiment of the moisture
barrier and breather membrane according to the present invention, in roll
form.
Figure 3 is a front elevation view of a partially installed exterior wall
system, comprising a wall sheathing, an embodiment of the moisture barrier and
breather membrane according.-to the present invention partially installed on
the wall
sheathing, and wall cladding partially installed on said moisture barrier and
breather
membrane.
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Figure 4 is a vertical sectional view of an exterior wall system
comprising a wall sheathing, an embodiment of the moisture barrier and
breather
membrane according to the present invention, and solid cladding.
Figure 5 is a vertical sectional view of an exterior wall system
comprising a wall sheathing, an embodiment of the moisture barrier and
breather
membrane according to the present invention, and plaster or stucco cladding.
DETAILED DESCRIPTION OF SPECIFIC
EMBODIMENTS OF THE INVENTION
Referring to Figure l , a moisture barrier and breather membrane 10
according to the present invention comprises a non-corrugated layer 12
laminated to
a corrugated layer 14. The corrugations should be between about 1/8 inch and
about
1/2 inch deep, preferably 1/4 inch deep. The centerlines of the corrugations
should
be between about 1/2 inch and about 2-1/2 inches apart, preferably 1-1/2
iliches. The
laminating is accomplished by applying intermittent strips of hot asphalt-
based
adhesive to layer 12 and then applying layer 14 thereon. Although hot asphalt
adhesive is the preferred laminating adhesive, other compatible adhesives may
be
used.
In one embodiment, a layer of non-corrugated, asphalt-saturated
breather paper is laminated to a layer of corrugated asphalt-saturated
breather paper.
In another embodiment, a layer of non-corrugated, preferably non-coated,
porous
fibreglass mat is laminated to the layer of corrugated asphalt-saturated
breather paper.
This second embodiment is especially appropriate for use with plaster or
stucco
cladding, in that the porous fibreglass mat functions as a backing sheet
behind the
plaster or stucco to prevent the plaster or stucco from filling the
corrugation channels
but permits moisture to pass through it. In each case, the corrugations are
rigid
enough to resist crushing when cladding is applied.
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Referring to Figure 2, moisture barrier and breather membrane 10 may
then be wound into rolls of convenient size, and may have an optional lap
guide
marking 16 for ease of installation.
Referring to Figure 3, moisture barrier and breather membrane 10 can
be installed into an exterior wall system 26 between a wall sheathing 18 and a
wall
cladding 24. Wall cladding 24 may, for example, be wood siding, plastic
(vinyl)
siding, stucco, synethetic stucco, E.I. F. S . , or the like. Prior to
applying wall
cladding 24, sheets of moisture barrier and breather membrane 10 can be
unrolled
horizontally and fastened to wall sheathing 18, such that the corrugations of
layer 14
are vertically oriented on wall sheathing 18. After moisture barrier and
breather
membrane 10 has been installed, wall cladding 24 can then be applied.
Referring to Figures 1, 4, and 5, the installation of moisture barrier
and breather membrane 10 will result in wall cladding 24 being spaced away
from the
wall sheathing 18 without the need for additional furring materials such as
wood
strapping. Further, the space between layer 12 and the corrugations of layer
14
provides vertical drainage channels 20 for drainage of moisture that has
bypassed
layer 14. Also, when installed, the space between the corrugations of layer 14
and
wall sheathing 18 or wall cladding 24, as the case may be, provides vertical
air
channels 22 for the movement of air (and possibly drainage of moisture as
well).
To achieve these results, proper installation of moisture barrier and
breather membrane 10 is essential. Referring back to Figure 3, the sheets of
moisture
barrier and breather membrane 10 should be installed in rows on wall sheathing
18
starting at the bottommost edge of wall sheathing 18 and continuing upwards
toward
the topmost edge of wall sheathing 18. The rows of moisture barrier and
breather
membrane 10 should be positioned so that horizontal laps are shingle-style, in
that
higher rows of moisture barrier and breather membrane 10 overlap lower rows of
same. The corrugations of each higher row should overlap corrugations of the
adjacent lower row preferably about 2 inches so that drainage channels 20 and
air
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channels 22 are continuous over the full height of wall sheathing 18. For ease
of
installation, optional lap guide marking 16 serves as a guide as to an
appropriate
amount of overlap.
Referring to Figure 4, in respect of solid cladding, moisture barrier and
breather membrane 10 should preferably be installed on wall sheathing 18 with
layer
14 facing away from wall sheathing 18. Referring to Figure 5, for plaster or
stucco
cladding, however, moisture barrier and breather membrane 10 should preferably
be
installed on wall sheathing with layer 14 facing toward wall sheathing 18 so
as to
prevent intrusion of stucco into the corrugation channels.
Referring to Figures 3, 4, and 5, all moisture which bypasses wall
cladding 24 should preferably have ready access to drainage channels 20 or air
channels 22 for unrestricted drainage. Each installed row of moisture barrier
and
breather membrane 10 should direct the moisture onto the row below it, and
thence
to exit the wall system at the bottom by way of properly positioned flashing.
Allowances should be made for air entry at the bottom of exterior wall system
26,
and air channels 22 may be open to the attic or soffit space above exterior
wall
system 26. Intermittent spacer strips 28, preferably of treated wood, may be
installed
at the bottom edge of wall sheathing 18 to allow for air entry into air
channels 22.
All vertical joints 30 between sheets of moisture barrier and breather
membrane 10
should be taped, and all tie-ins to windows and other terminations should
similarly
be taped. A metal strip stucco edge 32 should be affixed at the bottom of
exterior
wall system 26 prior to applying stucco wall cladding 24.
Although a particular embodiment of the present invention has been
described above, it will be understood by those skilled in the art that
various changes
and modifications may be made without departing from the spirit or essential
attributes of the present invention. Accordingly, the scope of the invention
is to be
construed in accordance with the substance defined by the following claims.
