Note: Descriptions are shown in the official language in which they were submitted.
CA 02241920 2002-08-20
Title: SINGLE WYTHE WALL SYSTEM
TECHNICAL FIELD
The invention is directed to a single wythe masonry rain screen wall system
with
interior finish support clips for supporting interior sheathing such as
drywall and rigid
insulation board a distance from the interior surface of the masonry wall,
wherein the
wall system has the capacity to contain and redirect any water permeating
through the
masonry structure within a wet air cavity preferably behind a vapour barrier
or water
to resistant rigid insulation and drywall sheathing.
BACKGROUND OF THE ART
A rain screen wall system is conventionally used in climates where rain water
permeates through a vertical wall. This condition is generally due to
excessive
precipitation in wet climates and the air pressure differential across an
exterior wall
surface due to the effect of wind impacting a building structure.
A conventional rain screen wall system is constructed of a veneer exterior
masonry
wall an adjacent air cavity, insulation, vapour barner, a structural masonry
support
2o wall or other type of structural support wall and the interior finish such
as dry wall.
This conventional rain screen wall system is known as a "double wythe" wall
and
simply stated represents two parallel masonry walls jointed across an air
filled cavity
usually with wire or sheet metal ties, or with masonry units laid across the
air cavity at
regular intervals.
A double wythe wall is relatively expensive to build since the double wall
itself is
material and labour intensive, and since electrical services, plumbing
services etc.
must be embedded within the masonry structure during masonry construction. Due
to
the cost and complexity, such a wall system is not feasible for many low cost
projects.
3o The double wythe wall requires that two walls be constructed separately
with an
CA 02241920 1999-06-24
interior and exterior wall joined with ties or masonry units at intervals
across the air
cavity.
The air cavity serves to prevent moisture penetrating to the second parallel
interior
wall. Moisture passes through the exterior first wall and trickles down the
air cavity to
the base of the air cavity where it is allowed to flow out to the exterior of
the building
through weep holes. When electrical work and plumbing are installed hidden
within
the walls, a significant disadvantage of the double wythe wall results from
the practical
difizculties in coordinatvzg electrical work and plumbing throughout the
duration of the
to wall construction. The electricians, plumbers and masons must work side by
side and
together in a coordinated fashion. Often the result is that one trade works on
a wall
section while the other trade waits or relocates to a different work area. The
constant
relocation and waiting for work to be completed interferes with the natural
flow of
construction and significantly reduces efficiency.
1s
The need to coordinate the work of different trades in a single area reduces
the speed
of installation and increases its complexity since neither trade can work
independently
of the other. Conventional construction methods usually involve the
construction of
exterior walls to provide a weather proof or protected enclosure within which
2o electricians and plumbers can then work completely independently. However,
when a
double wythe wall is used and hidden electrical and plumbing services are
desired, the
coordination of masonry and electrical and plumbing works must proceed
simultaneously. The installation of electrical and plumbing services on the
interior .
surface of a masonry wall is considered unsightly for most non-industrial
buildings, and
25 therefore embedded or hidden services are usually specified by the owner or
architect.
The simplest wall system involves a single wythe masonry wall. A single wythe
wall is
considered to be low cost, however, it is very ineffcient in respect of energy
cost. The
capital cost of constructing a single wythe masonry wall construction over
time is
3o somewhat set off against the higher heating and cooling cost due to the low
insulating
value of the single wythe; wall. The single wythe wall suffers from a
significant
2
CA 02241920 1999-06-24
disadvantage since moisture from rain and wind. can permeate through the wall
resulting in dampness on the interior of the building and efflorescence. The
permeation
of low volumes of water through the wall is generally not a matter for concern
structurally, however, adjacent electrical services or other metal building
elements can
be short-circuited or corroded over time. The perception of such wall system
is that
the building is low quality and is usually appropriate for industrial or
warehousing use.
In general, when constnrcting a building envelope, a weather tight and
insulated the
enclosure must be maintained. The building envelope must also be structurally
and
1o chemically compatible v~rith adjoining components of the building.
Construction costs
and scheduling are highly dependent on the simplicity of construction methods
and the'
nature of materials used. Briefly stated, the simpler the building systems,
the more
separate individual trades are, and the more traditional the methods used, the
better.
Introducing seams or holes in a wall system significantly increases the labour
content
15 and opportunity for errors, moisture penetration or loss of insulating
properties. A
highly desirable feature of wall systems is in its adaptability different
typical building
environments and configurations without specialized components or materials.
In particular, the installation of electrical and plumbing services can
present several
2o problems in maintaining the building envelope. For example, cutting into
foam
insulation to embed electrical wires significantly degrades the building
envelope,
increases the likelihood of errors, involves extra labour and delay, all of
which are
highly undesirable.
25 Therefore, it is an object of the present invention to provide a simply
constructed rain
screen wall system which incorporates a wet air cavity to capture and redirect
any
moisture permeating through the exterior wall portion in a simple economic and
quickly built system.
3o It is a further object of the invention to completely separate the
construction of single
wythe masonry wall from the installation of electrical or other building
services.
CA 02241920 1999-06-24
It is a further object of t:he invention to provide a rain screen wall system
incorporating
insulation and interior sheathing in a manner which enables installation of
electrical
services without requiring significant intrusion into the insulation itself.
Further objects of the invention will be apparent from review of the
disclosure and
description of the invention below.
DISCLOSURE OF THI: INVENTION
1o The invention provides a rain screen wall system and a sheet metal interior
finish
support clip for constructing the rain screen building wall system with a
single wythe
structural masonry wall having an exterior surface and an interior surface and
a
plurality of hollow masonry units laid in a single wythe with mortar joints.
15 The clips permit construction of a single wythe masonry wall that has the
capacity to
contain any water permeating through the otherwise traditional masonry wall
within a
wet air cavity immediately adjacent the interior surface of the single wythe
masonry
wall and preferably behind a vapour barner or water resistant rigid
insulation. The wet
air cavity serves to redirect the permeating water outward through
conventional weep
2o holes at the base of the masonry wall.
The interior finish support clips extend perpendicular to the interior surface
of the
structural wall and are disposed in a spaced apart two dimensional array over
the
interior masonry wall surface, for example: in a two foot by two foot grid
pattern.
25 Each clip has a base for securing the clip in the mortar joints of the
structural wall
interior surface, a shank extending from the base and an interior finish
support head
disposed a distance from the base for supporting interior finish sheathing
mounted to
the head.
3o To locate the clip quickly and securely the clip includes block abutments
on the clip
shank for engaging the interior surface of the structural wall and for
longitudinally
4
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positioning the clip relative to the interior surface of the structural wall,
lateral
abutments on the clip base for engaging an interior surface of an adjacent
peripheral
wall within a hollow chamber of one said masonry block and for positioning the
clip
laterally relative to the interior surface of the structural wall, and an
anchor on the base
for resisting tensile pull-out forces on the clip from within the hollow
chamber.
Preferably the anchor is a mortar filled pocket on the base of the clip. When
the wall is
to be insulated, the clip shanks include insulation support abutments for
securing rigid
insulation between the structural wall and the interior sheathing. To aid in
the
installation and sealing c>f insulation, and to remove obstacles during
installation of
to electrical or plumbing services, the clips can be made in two portions with
a field
connection between the portions. A first portion is embedded in the masonry
wall
mortar joints and includes insulation support tabs. A second portion is field
connected
with self tapping screws for example and includes the drywall sheathing
support head.
The single wythe masonry wall system according to the invention is much less
expensive than a traditional two-wythe rain screen wall. Mason and electrician
labour
costs as well as construction material costs are reduced through use of clips
to support
and space apart insulation and drywall. A wet air cavity bounded by the
interior
surface of the masonry wall and either a vapour burner or water resistant
rigid
2o insulation contains watex permeating through the wall and redirects the
water through
weep holes at the base of the masonry wall.
Due to the uniform spacing of masonry units, the spacing of clips is
automatic. For
example, if an 8 high inch masonry block is used, the width is a standard 16
inches.
Drywall is provided in 4 foot wide boards of length a multiple of 2 feet,
namely 8 foot,
10 foot, 12 foot and 14 iFoot lengths. Rigid insulation is usually provided in
two foot
wide boards. Therefore if clips are positioned in a 2 foot by 2 foot grid
pattern,
drywall and insulation can be simply applied without modification of
traditional
installation techniques. 'The positioning of clips every third course of
masonry units
3o automatically positions clips in rows spaced vertically 2 feet apart. As
well the 16 inch
length of masonry blocks with interior hollow chambers permits simple lateral
spacing
CA 02241920 1999-06-24
by engaging the base of the clips inside the hollow cavities. A clip in every
third block
results in four foot spacing automatically. An additional clip midway between
results
in two foot spacing automatically. Therefore, the mason need not expend much
ei~ort
in quickly installing the clips in a 2 foot by 2 foot grid pattern appropriate
for
traditional insulation and drywall boards.
Preferably a dry air cavity is included bounded by the interior surface of the
drywall
sheathing and the insulation. The dry air cavity can conveniently house
electrical and
plumbing services in a manner which permits ease of installation and more
efficient
1o separation of the constnzction trades. The dry air cavity also protects the
services from
corrosion and exposure to moisture. Conventional systems require services to
be
installed within hollow masonry significantly reducing the speed and
efficiency of
construction.
~5 Further details of the invention and its advantages will be apparent from
the detailed
description and drawings included below.
BRIEF DESCRIPTION OF THE DRAWINGS
In order that the invention may be readily understood, two preferred
embodiments of
2o the invention will be described by way of example, with reference to the
accompanying
drawings wherein:
Figure 1 is a side perspective view of a typical middle wall clip with a
horizontal shank as drawn, and starting at the left, having a base with a
vertical tab for
25 embedding in a masonry wall mortar joint, a tab for engaging the interior
surface of the
masonry wall to locate the clip longitudinally, a pair of opposing insulation
board
support tabs and a hat section drywall supporting head having an outer flat
surface for
mounting drywall sheathing and an inner tab for retaining the rigid insulation
board;
Figure 2 is a like side perspective view of a typical floor clip for securing
the
3o insulation and drywall to a single wythe masonry wall at the base of the
wall;
CA 02241920 1999-06-24
Figure 3 is a variation of the floor clip shown in Figure 2 with a modified
outer
tab adapted to support a. wooden backing board for receiving nails to attach
baseboards or other trim to the drywall;
Figures 4, 5, and 6 show alternative variations to the clips shown
respectively
in Figs. 1, 2, and 3 where no insulation is to be supported and hence the
insulation
support tabs have been removed;
Figure 7 is an elevation sectional view through a typical wall and floor with
clips embedded in masonry mortar joints with rigid insulation installation
complete in
the lower section and drywall sheathing and drywall screws with baseboard
exploded
1o away to the right;
Figure 8 is a perspective view illustrating the installation of a floor clip
below
the bottom course of the masonry wall in the bottom mortar joint;
Figure 9 is a like perspective view illustrating the installation of a top
wall clip;
and
15 Figure 10 is an elevation view of a progressively installed wall system, at
the
left progressing to the right, showing clips installed in a masonry block
wall, insulation
boards and backing boards installed, and then drywall installed covering the
insulation.
2o DETAILED DESCRIPTION OF PREFERRED EMBODIIVVIENTS
With reference to Figures 7 and 10 in particular, the present invention
provides a rain
screen wall system with a single wythe masonry wall. The rain screen wall
system
provides and maintains a building envelope using conventional constructional
25 techniques and enables the separation of the construction of masonry from
the
installation of electrical ;>ervices. Insulation and dry wall are also
installed in a manner
which enables construction scheduling to follow a more flexible and convenient
progression.
3o The key component of this system is the provision of an array of interior
finish support
clips extending perpendicular to the interior surface of the structural wall
and disposed
CA 02241920 2004-07-13
in a two-dimensional spaced apart array. The detailed construction and method
of
installation will be described below.
With reference to Figure 7, the masonry wall ( 1 ) is constructed of a
plurality of
masonry units laid up in a single wythe joined with mortar joints (2). As
drawn, the
structural masonry wall ( 1 ) has an exterior surface (3) to the left and an
interior
surface (4) to the right. As indicated in Figures 7 and 10, a plurality of
interior finish
support clips (5,6,7) have a base (8) secured to the masonry wall (1)
extending
perpendicular to the interior surface (4) of the structural wall ( 1 ). Figure
10 shows the
l0 clips (5,6,7) disposed in a 2 foot by 2 foot spaced apart two-dimensional
array.
Figures 8 and 9 respectively show the installation and detailed construction
of the
bottom clip (7) and top clip (5). Each clip whatever its construction (5,6,7)
has a base
(8) secured to the structural wall interior surface, a shank (9) extending
from the base
(8) and an interior finish support head (10) disposed a distance from the base
(8).
As shown in Figures 7 and 8, interior finish sheathing (11) such as drywall,
for
example, is mounted to the heads (10) of each clip (5,6,7) with drywall screws
(12),
for example. As a result, an enclosed wet air cavity (13) is defined
immediately
adj acent the interior surface (4) of the structural wall ( 1 ) and external
the finish
interior sheathing ( 11 ).
As indicated in the alternative clips (6, 7) shown in Figures 4, 5 and 6, the
installation
of rigid insulation board ( 14) is optional. In Figure 7, rigid insulation
boards ( 14) are
disposed between the structural wall ( 1 ) and the interior finish sheathing (
11 ). The rigid
insulation boards ( 14) are supported by insulation support abutments
preferably formed
as sheet metal tabs (15, best seen in Figs 1-3) extending from the clip shanks
(9). When
no insulation (14) is used, the wet air cavity (13) is defined between
interior surface of
the structural wall (4) and the sheathing ( 11 ). When insulation ( 14) is
used, a wet air
cavity (13) is defined and further a dry air cavity (16) is defined between
the insulation
(14) and the interior finish sheathing (11). As shown in Figure 7, the
electrical service
conductors (17) and electrical enclosure housing (18) are conveniently
disposed within
CA 02241920 2002-10-15
the dry air cavity (16) such that they remain easily accessible for
installation and are not
exposed to the moisture contained within the wet air cavity (13). To maintain
the
insulating value, electrical housings (18) are surrounded by insulation (14).
Conveniently a small patch (19) of insulation is placed behind the cut out
insulation
board (14) to accommodate the housing (18). A permeable moisture backing (20)
alternatively can be positioned behind the insulation patch (19) to allow
moisture flow
between the patch (19) and masonry wall surface (4).
Also preferably a continuous vapour barrier is provided by flexible membrane
(21 )
1 o and flashing (22) positioned underneath the membrane (21 ) and masonry
wall ( 1 ).
Weep holes are provided at the base of the masonry wall as it is conventional
to
permit moisture to escape to the external wall surface (3). Therefore, the
insulation
can be completed prior to electrical installation. The vapour barner membrane
(21 )
can be then completed and interior sheathing (11) placed on the support heads
(10).
Referring to Figure 10, if necessary to support plumbing fixtures or other
structures
which hang on the interior of the finished wall, a wooden backing board (23)
can be
secured to the clips (5,6,7) with self tapping screws, for example, within the
dry air
cavity ( 16) as indicated in dashed outline in Figure 2. It can be seen from
Figure 7
2o that the flexible Sheet metal strips which comprise the clips (5,6,7)
enable insertion of
the rigid insulation board ( 14) by flexibly prying up the clips (5,6,7) when
necessary.
Once the insulation board (14) is in place, the clips (5,6,7) are retained by
their
resilience and are locked in place when the sheathing (11) is secured.
With reference to Figures 7, 8 and 9, preferably masonry units are hollow
blocks of
substantially uniform horizontal section with vertically extending peripheral
walls (24)
and hollow chambers (25). The base (8) of each clip (5,6,7) extends into these
hollow
chambers (25) in the embodiment illustrated in the drawings. Since the clips
(5,6,7,)
comprise a thin metal strip, the shank (9) of the clips (5,6,7) can be secured
within the
3o mortar joint (2) without substantially effecting the bonding action of the
mortar joint.
In general, the thickness of the mortar (2) is approximately 3/8tns of an inch
and
9
CA 02241920 1999-06-24
therefore a thin metal strip inserted in the mortar joint (2) is of little
consequence. In
order to longitudinally position the clip (5,6,7) relative to the interior
surface (4) of the
structural wall, the shank (9) of the clips each include a block abutment tab
(26). In
the embodiment , the block abutment tab (26) is a simple transverse sheet
metal
member which abuts the interior surface (4) of the adjacent masonry unit. By
this
simple means, the precise alignment of all clips (5,6,7) is ensured.
In order to laterally position the clip relative to the interior surface (4)
of the structural
wall (1), the base (8) of each clip (5,6,7) includes lateral abutment side
edges (27)
1o engaging an interior surivace of an adjacent peripheral wall (24) within
the hollow
chamber of the masonry blocks as best illustrated in Figure 9. Due to the
uniform
configuration of each masonry, as shown in Figure 10, the lateral spacing of
the clips
(5,6,7) is automatically accomplished by positioning a clip (5,6,7) in every
third block
and mid-way between the blocks in order to provide a two-foot horizontal
spacing. It
15 is a simple matter to adapt the width of the clip shank (9) to ensure a two-
foot
horizontal centre distance or any other desired distance depending on the
particular
configuration of blocks utilized in a wall.
As best indicated in Figure 7, the base (8) of each clip includes means to
anchor it
2o within the hollow chambers (25) of the masonry units to resist tensile pull
out forces
on the clip (5,6,7). A simple anchoring means is illustrated where the base
(8) includes
an upstanding vertical tab to form a pocket for filling with mortar (28) as
shown in
Figure 7. Therefore, tension on the clips (5,6,7) is resisted by the hardened
mortar
(28) held within the pocket of the base {8) and compression on the clips
(5,6,7) is
25 resisted by the block abutment tabs (26) as well as anchoring of the clip
shanks (9)
within the mortar joints (2).
In order to provide an alternative clip which enables easy insertion and
sealing of the
rigid insulation board (14), an alternative embodiment includes clips which
have a field
3o connection joining a first clip portion which includes the base and shank
to a second
clip portion including the; interior finish support head ( 10). As indicated
in Figures 1
CA 02241920 1999-06-24
through 6, the first and second clip portions can be joined simply with a
field
connection formed by an overlapping shank plate (9) and a self tapping screw
(29).
Therefore conveniently the base (8) and shank (9) can be inserted in the
mortar joint
(2) while constructing the masonry wall. Insulation can be installed between
the
insulation support tab (15) and thereafter the field connection can be
completed with
installation of the second clip portion and securing with field connection
self tapping
screw (29).
Depending upon the type of baseboard or floor finishing material that are
used, as
1o shown in Figure 7, the base board (30) can merely be attached with
adhesives to the
interior surface of the drywall sheathing (11). If mechanical fasteners such
as nails or
screws are required to fasten the baseboard, a floor level backing board (31)
as shown
in Figures 3 and 6 can be attached with self tapping screws or adhesives to
the interior
finish support head (10). As well, it will apparent to those skilled in the
art that
15 framing around the windows and doors is generally necessary. Conventional
wooden
or sheet metal studs can be used to supplement the above system to adequately
frame
doors and windows, inside and outside corners as required in conjunction with
the clips
(5,6,7).
2o In accordance with the above description, the system for constructing a
rain screen
wall is less complex than the conventional method of constructing a double
wythe
masonry wall with air cavity between the two parallel masonry walls. The
separation
of electrical and plumbing services from the masonry construction is a
significant
advantage in that more efficient scheduling of construction and organization
of
25 different trades results.
To recap, the masonry support wall is built being exterior to the building
with hollow
core chambers (25) filled with insulation if desired. During construction of
the
masonry wall, the clips (5,6,7) or merely their first portions including the
base and
3o shank are installed extending from the interior face (4) of the masonry
wall. Once the
m
CA 02241920 1999-06-24
mortar (2) is cured, rigid insulation boards ( 14) can be installed and
secured in place
abutting the insulation support tabs (15). A wet air cavity (13) is
automatically formed
to the required width by the positioning of the insulation support tabs (15).
The rigid
insulation boards ( 14) require no mechanical fasteners to hold them in place
since the
tabs ( 15) serve adequately for this function. If required, caulking or other
sealant can
be applied to provide a water tight seal between joints in the insulation
boards (14). A
vapour burner membrane (21) and flashing (22) trap and redirect permeating
water
within the wet air cavity (13) and the water to flows out weep holes at the
base of the
masonry wall. Electrical housings (18) and conductors (17) can therefore be
placed
to within the insulation board (14) and run without obstacle in the dry air
gap (16) formed
between the insulation board (14) and the drywall sheathing (11). If required,
backing
support boards (23) can also be provided within the dry air cavity to support
sinks,
handrails, or other building elements that hang on the finished drywall (11)
surface. As
shown in Figure 2, the backing board (23) is secured in place with screws (12)
to a
flange (32) which serves the dual function of clamping the adjacent insulation
board
(14) in place and providing means to screw the backing board (23) securely in
place.
The rain screen wall system results in a reduction in materials and labour
required as
compared to the building of a conventional doubt wythe wall. Construction
duration is
2o reduced and interior dampness and efflorescence eliminated. The wet air
cavity traps
permeating water whereas the dry air cavity provides a dry, accessible, and
convenient
area for installation of plumbing, wiring, and backing boards. The advantages
and
integrity of a traditional cavity wall rain screen system are retained while
significant
reduction in costs and construction labour results.
Although the above description and accompanying drawings relate to a specific
preferred embodiment as presently contemplated by the inventors, it will be
understood
that the invention in its broad aspect includes mechanical and fixnctional
equivalents of
the elements described and illustrated.
12
