Note: Descriptions are shown in the official language in which they were submitted.
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COMPOSITIONS AND METHODS FOR COATING SURFACES
FIELD OF THE INVENTION
[0001] An exterior building cladding system and methods of applying the
building
cladding system are described. The system is a weather resistive barrier and
decorative
system that is particularly effective as a covering system for buildings
having an exterior
wood substrate. The system includes a flexible waterproof base layer of
acrylic and
rubber that is adhered directly to a wood substrate, a mesh embedded in the
flexible
waterproof base layer and an acrylic stucco outer layer adhering directly to
the flexible
waterproof base layer. The system eliminates the need for building wrap while
providing
a moisture resistant and vapour permeable layer.
BACKGROUND OF THE INVENTION
[0002] The use of stucco as a construction material for exterior cladding on
commercial
and residential buildings is well known in the prior art. Stucco cladding
generally
consists of a mixture of Portland cement, sand, water, and sometimes small
quantities of
lime. Stucco is applied to a building exterior in a wet plastic state and
allowed to dry to
form a rough, durable exterior cladding. Generally, two or more coats of
stucco are
applied to a building exterior, including a base coat and a top coat. Stucco
can be
applied directly to various surfaces including brick or stone surfaces.
[0003] As is well known, wood frame construction is common for residential and
commercial buildings in North America. Wood frame construction generally
incorporates
exterior sheathing over the wood frame including Oriented Strand Board (OSB),
plywood, or particle board. As stucco does not readily adhere directly to wood
substrates, a mesh or lath is generally attached to the exterior sheathing
beneath the
stucco layers to give the stucco an anchor to attach to. As such, the mesh
layer creates
an additional layer that must be applied as part of the exterior cladding
process.
[0004] As stucco cladding is quite rigid and brittle, it is susceptible to
cracking due to
shifts in a building frame and/or foundation due to natural settling, and/or
due to
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expansion or contraction of building components caused by temperature and
humidity
changes. Being made from cement and sand, stucco cladding is quite porous and
is
easily penetrated by water, especially if cracks are present in the stucco.
[0005] Modern stucco has addressed some of the problems of traditional stucco
by
various means including incorporating acrylic-based finish coats over a
cementitious
base coat that are provided to reduce the risk of exterior surface cracking.
However,
surface cracking in acrylic-based finish coats is not completely eliminated
and water
penetration is still possible.
[0006] As water penetration can lead to costly water damage to the building
cavity,
modern buildings also include a vapour-permeable, water-resistant barrier
wrapped
around the entire exterior building surface beneath the stucco layer.
Traditionally,
asphalt-saturated paper was used as the weather barrier, but today there are
numerous
manufactured plastic-based sheets in the market for this use, generally
referred to as
"building wraps" or "building membranes". Such building wraps are described in
U.S.
Patent No. 7,148,160 and U.S. Patent No. 6,355,333.
[0007] As with wood surfaces, stucco does not readily adhere to building
wraps, with the
result being that a mesh or lath is generally required to be fastened to the
exterior of the
building wrap by means of fastening devices such as nails or staples. The use
of
fastening devices creates small puncture holes in the building wrap that
increases the
susceptibility of the building wrap to water leakage, defeating the purpose of
the building
wrap. If water does get underneath the building wrap, it often becomes trapped
between
the building wrap and the underlying substrate, which can lead to mold and
mildew
problems that can damage the building structure and lead to other problems. As
such,
drainage mats are sometimes used between the building wrap and the underlying
substrate to create space and a drainage path for trapped moisture to exit the
wall. This
creates yet another layer that must be applied in an exterior cladding
process.
[0008] As a result, the application of stucco as an exterior cladding on wood
substrate
structures can be a time-consuming, labor-intensive process due to the myriad
of layers
that are required to prevent moisture penetration into the building structure.
In some
constructions, there may be as many as five layers applied individually,
including a
building wrap, mesh or lath, drainage mat, stucco base coat, and stucco top
coat.
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[0009] Certain approaches to decrease time and labor costs for the application
of
exterior cladding systems involve the use of pre-fabricated composite material
products
that combine one or more necessary layers into one product that can be
installed as a
unit. U.S. Patent Application No. 2007/0051069 describes a composite building
material
that includes a building membrane, a spacer material for drainage, and a lath
bonded
into one unit. U.S. Patent No. 6,131,353 discloses a composite drainage mat
with a
weather barrier attached. U.S. Patent Application No. 2006/0101758 describes a
corrosion-resistant non-metal lath attached to a weather barrier. Pre-
fabricated
cementitious fiber wallboard panels coated with a water based acrylic are
described in
U.S. Patent No. 6,516,580.
[0010] As pre-fabricated composite systems still consist of the typical
exterior cladding
layers, there is still the same amount of material in the composite products
as there
would be if the layers came as individual units. This generally results in pre-
fabricated
rolls or sheets of composite products that are bulky, heavy, and awkward to
install,
requiring a large labor component for their installation. Once they are
installed, the
numerous joints between the sections must be sealed and/or the product must be
installed with sufficient overlap between the sections to decrease the chance
of water
penetration at the joint, however this increases the amount of product that
must be used.
As well, the pre-fabricated products are susceptible to damage during the
transportation
and handling of the products prior to installation.
[0011] Regardless of the shortcomings of stucco, it is still a very popular
exterior
cladding material due to its attractiveness, wide variety of color options,
durability, and
low price. A variety of products are available to decrease the susceptibility
of stucco
cladding to water penetration, however a review of the prior art shows there
is still a
need for an exterior stucco cladding system for wood substrate buildings that
is simple
and quick to install and prevents water penetration into the underlying wood
substrate
while still allowing water vapor to escape from the building structure.
SUMMARY OF THE INVENTION
[0012] In accordance with the invention, there is provided an exterior
building cladding
system and method for cladding a building having an exterior surface.
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[0013] More specifically, there is provided an exterior building cladding
system for
application to a building substrate comprising:
a flexible waterproof and water vapor permeable base layer composition of
acrylic and rubber for adhering directly to the building substrate;
a reinforcement mesh for embedding in the flexible waterproof and water vapor
permeable base layer composition prior to curing of the flexible waterproof
and
water vapor permeable base layer composition; and
an acrylic stucco outer composition for adhering directly to the flexible
waterproof
and water vapor permeable base layer composition.
[0014] In one embodiment of the invention, the system includes a joint sealing
system
for sealing joints in the building substrate, the joint sealing system
comprising:
a curable acrylic and cementitious joint sealing composition for adhering
directly
to joints within the building substrate; and
a joint reinforcement mesh for embedding in the joint sealing layer prior to
curing.
[0015] Preferably, the reinforcement mesh and joint reinforcement mesh are
made of
fiberglass.
[0016] In another embodiment, the flexible waterproof and water vapor
permeable base
layer includes rubber crumb from recycled tires of about size 40 mesh.
[0017] Preferably, the flexible waterproof and water vapor permeable base
layer
composition includes 55-65% solids by weight, including by weight: 18-23%
rubber
crumb; 1-2% TiO2; 2-3% hard resin acrylic solids; 12-13% soft resin acrylic
solids; and
25-30% CaCO3.
[0018] In further embodiments, the flexible waterproof and water vapor
permeable base
layer will have any or all of the following characteristics: a water vapor
permeability rate
of greater than 60 ng/Pa.s.m2; impermeability to liquid water for up to 1.75
hr exposure
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to liquid water; a density of 1.25-1.35 kg/Litre; a viscosity of 350-600 KcP
before curing;
a bond strength to plywood and oriented strand board (OSB) of greater than 5
psi after
2000 hours of weathering; a tensile strength of greater than 20 lbs/inch; fire
resistance;
and/or a smoke developed classification of less than 20.
[0019] In yet another embodiment, the flexible waterproof and water vapor
permeable
base layer composition includes 35-45% by weight volatile compounds.
[0020] In another embodiment, the flexible waterproof and water vapor
permeable base
layer composition includes about 17.1 g/Litre of volatile organic compounds
before
curing.
[0021] In a preferred embodiment, the flexible waterproof and water vapor
permeable
base layer composition is applied to a building substrate with about a film
thickness of 2
millimeters.
[0022] In one embodiment, the joint sealing layer composition includes acrylic
and
Portland cement at about a 1:1 by weight ratio.
[0023] In further embodiments, the cured joint sealing layer composition will
have any
one of or a combination of the following characteristics: an air leakage value
of less than
0.01 L/sec/m2; a coefficient of water absorption of 0.0009 or less; and/or a
bond strength
to concrete or OSB of greater than 0.1 MPa after 2 hours and greater than 0.3
MPa after
7 hours.
[0024] In another aspect of the invention, there is provided a method of
cladding a
building having an exterior surface comprising the steps of: applying a
flexible
waterproof and water vapor permeable base layer to the exterior surface;
embedding a
reinforcement mesh in the flexible waterproof and water vapor permeable base
layer;
allowing the flexible waterproof and water vapor permeable base layer to cure
to form a
cured base layer; and applying an acrylic stucco outer layer to the cured base
layer.
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[0025] In another embodiment, the method further comprises applying a joint
sealing
layer embedded with a joint reinforcement mesh to joints in the exterior
surface prior to
step a).
[0026] In accordance with the method, the reinforcement mesh and joint
reinforcement
mesh may be fiberglass.
[0027] In accordance with the method, the flexible waterproof and water vapor
permeable base layer and the joint sealing layer may have a composition
as.described
above.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] The invention is described with reference to the accompanying figures
in which:
Figure 1 is a perspective view of a layered exterior cladding system in
accordance with one embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
Overview
[0029] With reference to the figure, a layered exterior cladding system (ECS)
10 is
described.
[0030] As shown in Figure 1, the ECS 10 is preferably applied directly to a
frame
constructed wall with a wood-based substrate. As shown, the typical wood frame
wall
includes evenly spaced structural members 12 and exterior panels or sheathing
14. The
ECS can also be applied to non-wood substrates, such as cementitious-based
substrates and insulated concrete forms (ICF's) made of expanded polystyrene
foam
(EPS), with additional surface preparation. Importantly, the subject system
does not
require the use of metal fasteners and, as explained in greater detail below,
creates a
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watertight surface in which the underlying sheathing is not compromised by
penetrating
fasteners. In addition, the system eliminates the need for house wrap and wire
meshes.
[0031] In accordance with the invention, the ECS includes a joint sealing
system 16 that
is comprised of a first mesh layer 18, a joint compound 20, and a wall coating
system 22
that includes a second mesh layer 24, a flexible rubber basecoat 26, and an
acrylic
stucco finish coat 28.
Joint Sealing System
[0032] The joint sealing system 16 is designed to seal all the joints, seams,
holes, and
cracks in the frame constructed wall from moisture penetration.
[0033] First Mesh Layer
[0034] The first mesh layer 18 is preferably made of fiberglass and is
designed to
provide increased surface strength, flexibility, as well as impact and crack
resistance in
the ECS. The first mesh layer is typically manufactured in 8 inch (20.3 cm)
wide rolls and
cut to the required length at the job site. Table 1 shows desired properties
and test
values for the first mesh layer 18 and second mesh layer 24.
Table 1- Properties and Test Values for Reinforcing Mesh Layers 18, 24.
Property Test Method Units Test Value
Construction ASTM D3775 Warp (/in) 6.0
Weft /in 5.0
Weight ASTM D3776 Oz/yd' 4.3
Thickness ASTM D1777 /in 0.017
Weave - - Leno
Finish - - Alkali Resistant
Nominal Tensile ASTM D5035 Warp (lb/in) 185
Weft (lb/in) 220
Joint Compound
[0035] The joint compound 20 is a specially formulated acrylic-based compound
that is
flexible and can expand and contract with changes in the frame constructed
wall while
still retaining a seal between the joints. The joint compound is preferably
manufactured
as a plastic acrylic compound that is mixed on the job site with clean type 10
Portland
cement in a 1:1 ratio by weight, together with small amounts of water (if any)
to provide a
desired workability. Preferably, an approximately 2 mm (5/64 inch) thick layer
of the
mixed joint compound is applied within 2-3 hours to the joints and seams of
the wall by
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means of a trowel, with the joints and seams preferably no larger than 6.35 mm
(% inch)
wide. The first mesh layer 18 is pressed into the wet joint compound and the
joint
compound is feathered out smoothly over the first mesh layer and allowed to
set. The
initial setting time of the acrylic resin in the joint compound is generally
24 hours and the
cement in the compound generally fully cures in about 28 days. Generally, the
ambient
temperature must be 5 C (41 F) or greater during the application and curing
process.
Typically, only one coat of joint compound is needed. However, if a second
coat of joint
compound is needed to completely cover the first layer of mesh 10, the second
coat can
be applied after the initial setting time of approximately 24 hours. Desired
properties and
test data for the joint compound is provided in Table 2.
Table 2 - Performance Properties of Joint Compound 20
Property Test Method Test Criteria Test Result
Air Leakage ASTM E283 < 0.02 Usec/m <0.01 Usec/m
Coefficient of Water CEN-TC89 < 0.004 0.0009
Absorption
Bond Strength to UEAct Directive 2-hour > 0.1 MPa Pass
Concrete Section 3.2.1.3 7-hour > 0.3 MPa Pass
Bond Strength to UEAct Directive 2-hour > 0.1 MPa Pass
OSB Section 3.2.1.3 7-hour > 0.3 MPa Pass
Bond Strength to UEAct Directive 2-hour > 0.1 MPa Pass
Basecoat Section 3.2.1.3 7-hour > 0.3 MPa Pass
Wall Coating System
Second Mesh Layer
[0036] The second mesh layer 24 is normally the same material (fiberglass) as
the first
mesh layer 10 and serves the same function: to increase the surface strength,
flexibility,
and impact and crack resistance of the ECS. Table 1 outlines the technical
data for the
mesh layers. The second mesh layer is preferably manufactured in rolls 38
inches wide
(96.5 cm) and cut to length at the job site. When applied, as described below,
the edges
of adjacent mesh layers preferably overlap a minimum of 2 inches (5.1 cm).
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Flexible Basecoat
[0037] The flexible rubber basecoat 26 is made of an acrylic polymer
impregnated with
rubber crumb granules, preferably of about size 40 mesh, and preferably from
recycled
tires. Technical data and testing data for the basecoat is outlined in Table 3
and Table 4
below. The basecoat adheres directly to the wood substrate exterior panels of
the
building and provides a flexible waterproof coating in the building envelope.
The
basecoat is formulated to allow for the transmission of water vapor at a rate
greater than
60 ng/Pa.s.m2 at the recommended thickness (dry) of 1 - 1.4 mm (1/32 - 3/64
inch)
such that the basecoat when cured is permeable to vapor water molecules yet
impermeable to liquid water molecules. This allows for the building frame to
be protected
from water damage, yet prevents moisture from being trapped in the building.
As the
basecoat is an elastic polymer, it is flexible and is less susceptible to
cracking as the
building shifts or expands and contracts from thermal stresses.
Table 3 - Properties of Flexible Rubber Basecoat
Property Value
Solids by weight (wt%) 55 - 65
TiO2 wt% 1 -2
Rubber Crumb by weight (wt%) 18 - 23
Acrylic Solids (wt%)
Hard Resin (Minimum Film 2-3
Forming Temperature (MFFT)
15 - 20 C)
Soft Resin (MFFT <1 C) 12 - 13
CaCO3 wt% 25 - 30
Volatile Compounds (wt%) 35 - 45
Volatile Organic Compounds (g/Litre) 17.1
pH 8.0-9.0
Density (kg/Litre) 1.25-1.35
Required Viscosity (KcP) 350 - 600
Required Application Film Thickness (mm) 2
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Table 4 - Performance Properties of Flexible Rubber Basecoat
Property Test Method Test Criteria Test Result
Water Vapour ASTM E96 > 60 ng/Pa.s.m Pass
Transmission
Accelerated ASTM G23-81 2000 hours of No deleterious
Weathering exposure effects
Bond Strength after ICBO ES AC59 V.E > 5 psi Pass
Weathering to OSB
& Plywood
Freeze-Thaw ICBO ES AC59 V.D 10 freeze-thaw No deleterious
cycles effects
Salt-Spray ASTM B117-85 300 hours of No deleterious
Resistance exposure effects
Pliability CAN/CGSB 51-32- No cracking @ - Pass
M77 para. 5.10 C
Tensile Strength CAN/CGSB 51-32- > 20 lbs/inch Pass
M77 para. 5.
Water Resistance ASTM D 779-94 Recorded No permeance after
1 hr.45 min.
Flamespread CAN/ULC S102-07 Recorded 0
Flamespread Value
(FSV)
Smoke CAN/ULC S102-07 Recorded Smoke < 20
Development Developed
Classification (SDC)
[0038] The flexible rubber basecoat is applied in a plastic state, tinted or
untinted, over
the entire clean building surface and over the set joint compound in a layer
thick enough
to completely embed the second mesh layer 24 that is pressed into the basecoat
immediately after the application of the basecoat. The basecoat is troweled
smooth over
the second mesh layer and allowed to cure. Upon exposure to the atmosphere,
the
basecoat dries in approximately 24 hours in ideal conditions (21 C / 70 F at
50% R.H.)
by water evaporation and cures by the coalescence of the acrylic polymer in
the
basecoat to form a continuous film. During the application and curing of the
basecoat the
ambient temperature should be > 5 C (41 F) and the basecoat should be
protected from
rain. Only one layer of basecoat is necessary, however a second layer can be
applied
after the first layer has dried (approximately 24 hours) if needed.
[0039] Upon setting, the basecoat creates a continuous seamless waterproof
surface
over the coated surface and with minimal maintenance will generally last the
life of the
building. The second mesh layer in the basecoat acts as a support structure
for the
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rubber basecoat, much like the steel belt in a rubber tire supports a rubber
tire tread. As
known to those skilled in the art appropriate flashing, termination strips,
corner beads
and/or other detailing structures can be incorporated in and around window and
door
openings and corners.
Acrylic Stucco Finish Coat
The acrylic stucco finish coat 28 is a typical stucco containing acrylic that
is well known
to those versed in the art. In the preferred embodiment, the finish coat is
tinted to any
color and is of fine, medium, or coarse texture. The finish coat is troweled
directly on top
of the rubber basecoat 26 (after the basecoat has cured) in a thickness just
greater than
the larger aggregate in the finish coat. The finish coat generally dries in 24
hours and
with minimal maintenance will generally last the life of the building.
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