U.S. patent application number 13/179583 was filed with the patent office on 2012-01-19 for high strength light-framed wall structure.
Invention is credited to Gregory S. Bergtold, Dean P. DeWildt.
Application Number | 20120011792 13/179583 |
Document ID | / |
Family ID | 45465799 |
Filed Date | 2012-01-19 |
United States Patent
Application |
20120011792 |
Kind Code |
A1 |
DeWildt; Dean P. ; et
al. |
January 19, 2012 |
HIGH STRENGTH LIGHT-FRAMED WALL STRUCTURE
Abstract
A light-framed wall structure contains a wall frame of studs, a
bottom plate and a single top plate that together define a stud
cavity; exterior sheathing attached to the wall frame and covering
the stud cavity; and a polyurethane foam within the stud cavity and
affixed to the exterior sheathing, studs, bottom plate and top
plate.
Inventors: |
DeWildt; Dean P.; (Midland,
MI) ; Bergtold; Gregory S.; (Midland, MI) |
Family ID: |
45465799 |
Appl. No.: |
13/179583 |
Filed: |
July 11, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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61364413 |
Jul 15, 2010 |
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Current U.S.
Class: |
52/309.4 ;
52/483.1; 52/745.09 |
Current CPC
Class: |
E04C 2/386 20130101 |
Class at
Publication: |
52/309.4 ;
52/483.1; 52/745.09 |
International
Class: |
E04B 2/48 20060101
E04B002/48; E04C 2/20 20060101 E04C002/20; E04B 2/02 20060101
E04B002/02 |
Claims
1. A light-framed wall structure comprising: (a) studs spaced apart
from one another in a range of nominally 16 to nominally 24 inches
on center; (b) a bottom plate and a single top plate spanning the
studs and attached to opposing ends of the studs such that the
studs, top plate and bottom plate define a wall frame having
opposing interior and exterior surfaces with the studs, top and
bottom plate further defining a stud cavity within the wall frame,
the stud cavity having a height extending from bottom plate to top
plate and a width extending from one stud to another stud; (c)
sheathing spanning the width and height of the stud cavity and
overlapping the studs and attached to at least one of the exterior
and interior surfaces of the wall frame; and (d) polyurethane foam
forming a seal around the inside perimeter of the stud cavity and
affixed to the sheathing material on at least one surface of the
wall frame, the stud, top plate and bottom plate where the
polyurethane foam extends at least 1.5 inches over the sheathing,
studs, top plate and bottom plate along the perimeter and further
is present at an average thickness of at least 3.5 inches over the
volume of the stud cavity within six inches of the top plate;
wherein the light-framed wall structure is free of metal corner
connectors or reinforcements comprising a box-shaped section
against which the studs, bottom plate and top plate abut.
2. The light-framed wall structure of claim 1, wherein the studs
are 2.times.4 dimensional building elements spaced apart from one
another a nominal 24 inches on center.
3. The light-framed wall structure of claim 1, wherein the
sheathing material is selected from structural insulated sheathing,
rigid insulated sheathing and gypsum board.
4. The light-framed wall structure of claim 1, wherein the
sheathing material is structural insulated sheathing.
5. The light-framed wall structure of claim 1, wherein the
polyurethane foam entirely covers any sheathing attached to at
least one of the interior and exterior surfaces of the wall frame
that would otherwise be exposed within the stud cavity.
6. The light-framed wall structure of claim 1, wherein the
polyurethane foam has a thickness anywhere in the stud cavity of at
least one and one half inches thick as measured perpendicularly
from the sheathing material to which the polyurethane foam is
affixed.
7. The light-framed wall structure of claim 1, wherein the
sheathing is exterior sheathing attached to the exterior surface of
the wall frame.
8. The light-framed wall structure of claim 7, further comprising
interior sheathing spanning the width and height of the stud cavity
and overlapping the studs and attached to the interior surface of
the wall frame.
9. A light-framed wall structure comprising: (a) studs nominally
spaced apart from one another 24 inches on center; (b) a bottom
plate and a single top plate spanning the studs and attached to
opposing ends of the studs such that the studs, top plate and
bottom plate define a wall frame having opposing interior and
exterior surfaces with the studs, top and bottom plate further
defining a stud cavity within the wall frame, the stud cavity
having a height extending from bottom plate to top plate and a
width extending from one stud to another stud; (c) exterior
sheathing spanning the width and height of the stud cavity and
overlapping the studs and attached to the exterior surface of the
wall frame; and (d) polyurethane foam within the stud cavity and
affixed to the exterior sheathing material, studs, top plate and
bottom plate defining the stud cavity, the polyurethane foam having
an average thickness of at least 0.5 inches within the stud cavity;
wherein the light-framed wall structure is free of metal corner
connectors or reinforcements comprising a box-shaped section
against which the studs, bottom plate and top plate abut.
10. A process for making the light-framed wall structure of claim
1, the process comprising the following steps: (a) assembling studs
spaced apart from one another in a range of nominally 16 to
nominally 24 inches on center between a single top plate and a
bottom plate so as to form a wall frame having opposing interior
and exterior surfaces and defining a stud cavity between the studs
and top and bottom plates and affixing the studs to the top and
bottom plates; (b) affixing sheathing to at least one of the
exterior and interior surfaces of the wall frame over the studs and
stud cavity; and (c) disposing a polyurethane foam into the stud
cavity so as to form a seal around the inside perimeter of the stud
cavity that is affixed to the sheathing material on at least one
surface of the wall frame, the studs, top plate and bottom plate
defining the stud cavity, the polyurethane foam being disposed in
such an amount so as to have an average thickness of at least 3.5
inches in the stud cavity within six inches of the top plate and
extending at least 1.5 inches over the studs, top plate, bottom
plate and sheathing around the inside perimeter of the stud cavity;
wherein the light-framed wall structure is free of metal corner
connectors or reinforcement comprising a box-shaped section against
which the studs, bottom plate and top plate abut.
11. The process of claim 10, wherein the studs are 2.times.4
dimensional building elements and they are assembled spaced apart
from one another nominally 24 inches on center.
12. The process of claim 10, wherein the sheathing is selected from
structural insulated sheathing material, rigid insulated sheathing
and gypsum board.
13. The process of claim 10, wherein the polyurethane foam is a
spray polyurethane foam and step (c) includes spraying the
polyurethane foam into place.
14. The process of claim 10, wherein polyurethane foam is disposed
so as to entirely cover any sheathing attached to at least one of
the interior and exterior surfaces of the wall frame that would
otherwise be exposed within the stud cavity.
15. The process of claim 10, wherein the polyurethane foam is
disposed so as to have an average expanded thickness of at least
1.5 inches within the stud cavity as measured perpendicularly from
the sheathing to which the polyurethane foam is affixed.
16. The process of claim 10, wherein the polyurethane foam is
disposed to a greater thickness proximate to the top plate than on
average within the stud cavity.
17. The process of claim 10, comprises affixing sheathing to both
the exterior and the interior surfaces of the wall frame over the
studs and stud cavities.
18. The process of claim 10, wherein the wall frame has multiple
stud cavities defined therein by the studs, top plate and bottom
plate and wherein step (b) includes affixing sheathing over
multiple stud cavities and step (c) includes disposing polyurethane
as described into multiple stud cavities.
19. A building structure comprising the light-framed wall structure
of claim 1.
Description
CROSS REFERENCE STATEMENT
[0001] This application claims the benefit of U.S. Provisional
Application No. 61/364,413, filed Jul. 15, 2010, the entire content
of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a light-framed wall
structure, a process for making the light-framed wall structure and
a building containing the light-framed wall structure.
[0004] 2. Description of Related Art
[0005] There is a continuous drive in the building industry to
decrease building costs while increasing thermal insulating
properties and maintaining structural integrity under building
codes. Wall framing members are one type of building element that
plays a role in all aspects of this drive. The large number of
framing members in a light-framed wall structure inherently makes
them a notable contributor to the building cost. Framing members
also have a relatively low insulation value and serve as a means
for thermal shorts through a wall structure since insulation is
often applied only between the framing members. From a cost and
insulation perspective, it would be desirable to reduce the number
of framing members in a light-framed wall structure.
[0006] However, building codes specify that wall structures must
meet certain structural integrity criteria. In particular, a wall
in a building structure must withstand lateral and transverse loads
resulting from wind and earthquakes as well as axial loads due to
structure weight, snow, and floor loads. The International
Residential Building Code (IRC) and International Building Code
(IBC) provide prescriptive solutions and minimum standards for
walls that meet code structural integrity criteria. The
prescriptive solutions commonly utilize 2.times.4 studs spaced
16-inch on center, or 2.times.6 studs spaced 24-inches on center,
with a double top plate over the studs to distribute axial point
loads. Additionally, the IRC and IBC allow for a single top plate
provided that roof rafters or floor joists align within one inch of
stud centerlines so as to directly transfer their load to a stud
below. While such a wall design reduces building elements by using
a single top plate, the necessary careful alignment of roof rafters
or floor joists reduces flexibility in building designs and
construction. The IRC and IBC allow for custom engineered wall
designs provided the wall has sufficient load bearing
properties.
[0007] It is desirable to develop a light-framed wall structure
that can support axial point, transverse and lateral loads
sufficiently to meet IRC and IBC requirements for structural
integrity but by using fewer framing members, especially if such a
wall structure requires only a single top plate and alignment of
second floor studs and/or roof rafters and trusses did not have to
align within one inch of the wall structure studs. Even more
desirable is such a light-framed wall structure that would
eliminate the problem of thermal shorts through the wall caused by
the studs by including an insulating layer that extends over the
studs.
BRIEF SUMMARY OF THE INVENTION
[0008] The present invention provides a solution to the desire for
a light-framed wall structure that can support axial point,
transverse and lateral loads sufficiently to meet IRC and IBC
requirements for structural integrity with fewer framing members
and in particular such a wall structure requiring only a single top
plate where alignment of second floor studs and/or roof rafters and
roof trusses do not have to align within one inch of the wall
structure studs. Even more, the present invention can provide a
light-framed wall structure that eliminates thermal shorts through
the wall caused by the framing elements by including an insulating
layer that extends over the studs.
[0009] Surprisingly, the objectives of the present invention are
achievable with a stud spacing in a range of nominally 16 inches to
nominally 24 inches on center, even when using a single top plate,
sheathing overlaying the studs and spanning the spacing between the
studs and the presence of polyurethane foam disposed in the stud
cavity adhering to the studs and the sheathing.
[0010] Light-framed wall structures of the present invention
surprisingly can concomitantly support (that is, withstand; resist
without failure) axial point loads of 2500 pounds or more, even
3500 pounds or more, and even 4000 pounds or more (and desirably
uplift loads of 1500 pounds or more even 2000 pounds or more)
according to ASTM method E72, Section 9 as modified in the Example
below (exclusion of the I-beam along the top plate); lateral loads
of 500 pounds per linear foot (plf) or more, even 750 plf or more,
and even 1000 plf or more according to ASTM method E72, Section 14;
and transverse loads of 150 pounds per square foot (psf) or more,
even 200 psf or more, and even 250 psf or more according to ASTM
method E72, Section 11.
[0011] In a first aspect, the present invention is a light-framed
wall structure comprising: (a) studs spaced apart from one another
in a range of nominally 16 to nominally 24 inches on center; (b) a
bottom plate and a single top plate spanning the studs and attached
to opposing ends of the studs such that the studs, top plate and
bottom plate define a wall frame having opposing interior and
exterior surfaces with the studs, top and bottom plate further
defining a stud cavity within the wall frame, the stud cavity
having a height extending from bottom plate to top plate and a
width extending from one stud to another stud; (c) sheathing
spanning the width and height of the stud cavity and overlapping
the studs and attached to at least one of the exterior and interior
surfaces of the wall frame; and (d) polyurethane foam forming a
seal around the inside perimeter of the stud cavity and affixed to
the sheathing material on at least one surface of the wall frame,
the stud, top plate and bottom plate where the polyurethane foam
extends at least 1.5 inches over the sheathing, studs, top plate
and bottom plate along the perimeter and further is present at an
average thickness of at least 3.5 inches over the volume of the
stud cavity within six inches of the top plate; wherein the
light-framed wall structure is free of metal corner connectors or
reinforcements comprising a box-shaped section against which the
studs, bottom plate and top plate abut.
[0012] In a second aspect, the present invention is a light-framed
wall structure comprising: (a) studs nominally spaced apart from
one another 24 inches on center; (b) a bottom plate and a single
top plate spanning the studs and attached to opposing ends of the
studs such that the studs, top plate and bottom plate define a wall
frame having opposing interior and exterior surfaces with the
studs, top and bottom plate further defining a stud cavity within
the wall frame, the stud cavity having a height extending from
bottom plate to top plate and a width extending from one stud to
another stud; (c) exterior sheathing spanning the width and height
of the stud cavity and overlapping the studs and attached to the
exterior surface of the wall frame; and (d) polyurethane foam
within the stud cavity and affixed to the exterior sheathing
material, studs, top plate and bottom plate defining the stud
cavity, the polyurethane foam having an average thickness of at
least 0.5 inches within the stud cavity; wherein the light-framed
wall structure is free of metal corner connectors or reinforcements
comprising a box-shaped section against which the studs, bottom
plate and top plate abut.
[0013] In a third aspect, the present invention is a process for
making the light-framed wall structure of the first aspect, the
process comprising the following steps: (a) assembling studs
nominally spaced 24 inches on center between a single top plate and
a bottom plate so as to form a wall frame having opposing interior
and exterior surfaces and defining a stud cavity between the studs
and top and bottom plates and affixing the studs to the top and
bottom plates; (b) affixing exterior sheathing to the exterior
surface of the wall frame over the studs and stud cavity; and (c)
disposing a polyurethane foam into the stud cavity onto the
exterior sheathing and against the studs and top and bottom plates
so as to have an average expanded thickness of at least 0.5 inches
within the stud cavity and so that the polyurethane foam attaches
to the exterior sheathing, studs and top and bottom plates of the
stud cavity.
[0014] In a fourth aspect, the present invention is a building
structure comprising the light-framed wall structure of the first
aspect.
[0015] The light-framed wall structure and process of the present
invention is useful in constructing buildings. The building of the
present invention is useful as a building structure for many types
of use including residential housing and light commercial
buildings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 illustrates an embodiment of the light-framed wall
structure of present invention with FIG. 1(A) illustrating a
cutaway view looking down from the top from under the top plate and
FIG. 1(B) illustrating a view from the interior surface side.
[0017] FIG. 2 illustrates an embodiment of the light-framed wall
structure of the present invention illustrating a view from the
interior surface side.
DETAILED DESCRIPTION OF THE INVENTION
[0018] "ASTM" refers to American Society for Testing and Materials
and is used to designate a test method by number as published by
ASTM. Test numbers refer to the most recent test published prior to
the priority date of this document unless otherwise specified by a
date using a hyphenated suffix after the test number.
[0019] "Multiple" means two or more. "And/or" means "and, or as an
alternative". All ranges include endpoints unless otherwise
indicated.
[0020] "Length", "width" and "thickness" are three mutually
perpendicular dimensions of an object. Length is a dimension having
a magnitude equivalent to the largest magnitude dimension of the
length, width and thickness. Thickness has a magnitude equal to the
smallest magnitude of the length, width and thickness. Width has a
magnitude equal to the length, thickness, both the length and
thickness, or a magnitude somewhere between that of the length and
thickness.
[0021] "Light-framed wall structure" refers to a wall structure
comprising studs spaced apart from one another and attached at
opposing ends to top plate and bottom plate members. The studs, top
plate and bottom plate define a wall frame that defines stud
cavities between studs and the top and bottom plates.
[0022] "Polyurethane foam" refers to a polymeric foam wherein the
polymeric matrix of the foam comprises polyurethane linkages formed
by reacting isocyanate functionalities with polyol and/or other
reactive additives. The polyurethane foam has an isocyanate index
in a range of 95 or higher, preferably 100 or higher, still more
preferably 120 or higher and yet more preferably 150 or higher. At
the same time the isocyanate index is desirably 350 or lower,
preferably 300 or lower, more preferably 250 or loser and yet more
preferably 200 or lower. Determine isocyanate index by multiplying
100 times the actual amount of isocyanate used divided by the
theoretical amount of isocyanate required to stoichiometrically
react with all of the polyol and other isocyanate-reactive
additives in the foam formulation.
[0023] In one aspect the present invention is a light-framed wall
structure. In the light-framed wall structure of the present
invention the studs are spaced apart nominally 16 to 24 inches on
center. Particularly common spacings suitable for use in the
present invention include nominally 16 inches on center, nominally
19.2 inches on center and nominally 24 inches on center. "Nominal"
values include tolerances from the specific value that are commonly
accepted in the construction industry. For example, actual spacing
can be off from a nominal value by as much as 0.125 inches or less,
preferably 0.0625 or less, more preferably 0.0312 inches or less
from being spaced exactly the nominal value. Spacing "on center"
refers to a measurement taken from the center of one stud to the
center of the next neighboring stud. Typically, studs are aligned
such that the surface of one stud faces the surface of another stud
and the distance on center is measured from the center of the
thickness (center of an edge) of one stud to the center of the
thickness (center of an edge) on a neighboring stud.
[0024] Studs can be any stud known or yet to be used in
constructing light-framed wall structures. Suitable studs include
what is commonly known as 2.times.4 and/or 2.times.6 dimensional
building elements, where the numbers designate the nominal
thickness and width of the building elements in inches rounded up
to the nearest inch. Typically, 2.times.4 elements are nominally
1.5 inches thick and nominally 3.5 inches wide and 2.times.6
elements are nominally 1.5 inches thick and nominally 5.5 inches
wide. Often studs are made from lumber (wood) or metal (typically,
thin gauge steel). Studs, as well as top and bottom plates, have
opposing surfaces, edges and ends. The width of a stud and bottom
plate separates opposing edges, thickness separates opposing
surfaces and length separates opposing ends.
[0025] The light-framed wall structure of the present invention is
further characterized by having a bottom plate and a single top
plate, each spanning multiple studs. Bottom plates and top plates
can be any currently known or yet to be developed material for
light-framed wall structures. As with the studs, the bottom plate
and top plate are often dimensional building elements such as
2.times.4 or 2.times.6 materials. It is common to use dimensional
building elements of the same thickness and width for the top
plate, bottom plate, or both top plate and bottom plate as is used
for the studs they span. It is also common to use top and bottom
plates made of the same material as the studs they span.
[0026] As the name suggests, bottom plates and top plates span the
bottom and top of the studs, respectively, to form the wall frame
of the light-framed wall structure. Studs have one of their ends
attached to a surface of a bottom plate and their opposing end
attached to a surface of a top plate. It is common to attach the
studs to the top and bottom plates using nails (for example, steel
nails) when the building elements are wood and screws or pins when
the building elements are metal. In such a configuration,
neighboring studs and the top and bottom plates spanning those
studs define a stud cavity having a height extending from the
bottom plate to the top plate (the length of the studs) and a width
extending from one stud to a neighboring stud. It is common for the
studs to have an orientation in the light-framed wall structure
such that the surface of one stud faces the surface of a
neighboring stud and the facing surfaces are both exposed within a
stud cavity. At the same time, one of the edges of each stud (the
inside edge) is on what shall be called the "interior" surface of
the wall frame and the opposing edge of the stud (the outside edge)
is on what shall be called the "exterior" surface of the wall
frame. Similarly, a surface of the top plate faces a surface of the
bottom plate and both of these facing surfaces are exposed within a
stud cavity while one of the edges of each of the top and bottom
plates is on the interior surface of the wall frame and the
opposing edge is on the exterior surface of the wall frame.
[0027] The wall frame achieves sufficient strength without
requiring metal corner connectors having box-shaped intermediate
sections as taught in U.S. Pat. No. 7,882,666 ('666). Reference
'666 discloses a prefabricated building component that comprises a
frame of lumber components in a rectangular orientation and joined
together with metal corner connectors. Each corner connector
comprises a metal box against which the lumber components abut.
These corner reinforcements are necessary components of the '666
structure. However, the present invention is free of metal corner
connector having box-shaped intermediate sections against which the
studs, top plate and bottom plate abut. Applicants have discovered
a method of achieving suitable strength, particularly racking
strength, with the wall structure of the present invention without
requiring such metal corner reinforcements.
[0028] As noted, the wall frame has a stud cavity defined therein.
While teachings, including descriptions and claims, herein
generally refer to "a" stud cavity defined within a wall frame by
studs, top and bottom plates, the wall frame can and typically does
have multiple stud cavities defined by the studs, top and bottom
plates of the wall frame. The wall frame of the light-framed wall
structure of the present invention can have defined therein one or
more than one stud cavity (that is, reference to "a" stud cavity
does not imply there is only a single stud cavity in the wall
frame). Teachings herein, when referring to "a" stud cavity, can
and desirably do apply to more than one and most desirably apply to
each stud cavity in a wall frame of the light-framed wall structure
when the light-framed wall structure has multiple stud cavities
defined therein. For example, teaching that exterior sheathing
fully covers the stud cavity should be understood as meaning
exterior sheathing preferably fully covers multiple stud cavities
if the wall frame contains more than one stud cavity, and more
preferably covers each stud cavity of the wall frame. Similarly,
teaching about polyurethane within a stud cavity should be
understood as desirably being applicable to multiple and preferably
each stud cavity of the wall frame when the wall frame contains
more than one stud cavity.
[0029] Wall frames can also have defined therein sub-cavities
within a stud cavity. A sub-cavity is a portion of a stud cavity
that does not extend from a base plate to a top plate. For example,
headers and sills extending from one stud to a neighboring stud
divide a stud cavity into multiple sub-cavities for framing a
window into a wall frame. One of the sub-cavities is sized to
accommodate the window and is not filled with polyurethane foam or
covered with exterior or interior sheathing. However, the
sub-cavities that are typically above and/or below the window are
desirably treated as described herein for a stud cavity in the
present invention--that is, the sub-cavities are covered with
sheathing and polyurethane foam disposed within the sub-cavity and,
generally, enclosed with both exterior and interior sheathing. In
like manner, framing for a door in a wall frame can result in
creation of separate sub-cavities of a stud cavity, one to fit the
door and the other to be desirably treated in like manner as a
cavity of the present invention. It is desirable to treat
sub-cavities as stud cavities according to the teachings herein in
order to achieve an optimally insulated and reinforced wall
structure of the present invention, except for those sub-cavities
that accommodate a functional component such as a door or
window.
[0030] The light-framed wall structure of present invention
comprises sheathing that spans the width and height of the stud
cavity thereby covering (typically, entirely covering) the stud
cavity and overlapping the studs of the wall frame. The sheathing
overlaps and attaches to edges of the studs on a surface of the
wall frame. The sheathing can be exterior sheathing attached to the
exterior surface of the wall frame, interior sheathing attached to
the interior surface of the wall frame, or the light-framed wall
structure can comprise both exterior and interior sheathing
attached to their corresponding surfaces of the light-framed wall.
It is desirable that the light-framed wall structure comprise at
least exterior sheathing. Exterior sheathing serves as a protective
barrier from outside elements and can further serves as thermal
insulation as well as structural reinforcement
[0031] Suitable sheathing includes panels of foam sheathing (for
example, polymeric foam board that can comprise facer material on
one or more than one surface or that is free of facer material),
wood sheathing (for example, oriented strand board or plywood),
fibrous structural board (for example, fiberboard), composite
structures such as structural insulated sheathing, gypsum board, or
paneling of any composition. Typically, exterior sheathing is
selected from foam sheathing, wood sheathing, fibrous structural
board, gypsum board and composition structures such as structural
insulated sheathing. Typically, interior sheathing is selected form
gypsum board and paneling. Gypsum board refers to what is also
known as drywall or plasterboard.
[0032] Desirably, the present invention includes exterior
sheathing. Even more desirably, the exterior sheathing
simultaneously increases structural integrity, barrier properties
and thermal insulation to the light-framed wall structure. In that
regard, particularly desirable exterior sheathing comprises an
insulating foam element and a structural sheathing element such as
wood sheathing or fibrous sheathing in a single product that can be
applied onto a wall frame in a single step. Such a product is
commonly referred to as structural insulated sheathing (SIS). A SIS
product provides a combination of thermal insulation, water and air
barrier properties and structural strength to the light-framed wall
structure of the present invention. An example of a particularly
desirable exterior sheathing that provides a combination of
structural integrity, barrier properties and thermal insulation in
a single sheathing material is STYROFOAM SIS.TM. Brand Structural
Insulating Sheathing (STYROFOAM SIS is a trademark of The Dow
Chemical Company). ZIP insulated system sheathing is also suitable
(available from Huber Engineered Woods LLC) that provides
structural integrity, barrier properties and thermal insulation
together in a single sheathing material.
[0033] Use of thermally insulating exterior sheathing, such as SIS
or insulating foam panels, in the present invention results in a
thermally insulating layer that completely covers studs by
overlaying the exterior surface of the wall frame. As a result, the
thermally insulating exterior sheathing precludes the studs from
efficiently acting as thermal shorts through the light-framed wall
structure. Reducing, even eliminating studs from acting as thermal
shorts through a wall provides a superior thermally insulated wall
structure over more common light-framed wall structures containing
thermal insulation only in stud cavities.
[0034] The sheathing is attached to a surface of the wall frame by
any means now known or yet to be discovered in the building
industry. Examples of suitable means include any one or any
combination of more than one of the following: mechanical fasteners
(such as screws, pins, nails and staples), liquid adhesives (such
as caulks and glues), and foam adhesives (such as thermoset foams
including polyurethane spray foam), and plasticized adhesives (such
as hot-melt glue). It is desirable to use an adhesive to adhere the
sheathing to the wall frame, either alone or in combination with
mechanical fasteners, with a continuous bead of adhesive along the
wall frame members. Maximizing the surface of the wall frame to
which the sheathing attaches maximizes the mechanical strength of
the resulting light-frame wall structure.
[0035] The stud cavity of the light-framed wall structure desirably
contains polyurethane foam around the inside perimeter of a stud
cavity and affixed to the studs, top plate, bottom plate and
sheathing (that is, affixed simultaneously to each of these wall
structural elements). The polyurethane foam adjoins the building
elements together around the inside perimeter of the stud cavity,
joining the sheathing to the studs, top plate and bottom plate much
like a fillet weld. The polyurethane foam desirably extends a
distance of at least 1.5-inches over the studs, top plate, bottom
plate and sheathing around the inside of the perimeter of the stud
cavity to ensure a good seal and strong structural reinforcement of
the wall structure. For optimal sealing performance and structural
integrity the polyurethane foam should be continuous around the
inside perimeter of the stud cavity. However, occasional breaks or
spaces in the foam around the perimeter can be acceptable.
[0036] The polyurethane foam desirably has a greater expanded
thickness proximate to the top plate than on average within a stud
cavity. Polyurethane foam proximate to the top plate can support
and stabilize the top plate from bending and twisting under load.
Stabilization of the top plate is achievable without requiring the
same thickness of polyurethane foam throughout the stud cavity.
Therefore, a cost effective way to stabilize the top plate is to
dispose polyurethane foam to a thicker expanded thickness proximate
to the top plate. The polyurethane foam is present at an average
thickness of 3.5-inches within the volume of the stud cavity within
six inches, preferably within eight inches, more preferably within
ten inches of the top plate. Measure polyurethane foam thickness
perpendicular to the sheathing to which it is affixed.
[0037] To further increase thermal insulating properties of the
wall it is desirable that the spray polyurethane foam has an
average expanded thickness of at least 0.5 inches within the stud
cavity and desirably has an expanded thickness of at least one
inch, preferably at least 1.5 inches and more preferably at least
two inches within the stud cavity. Measure the expanded thickness
of the polyurethane foam perpendicular to the sheathing to which
the polyurethane is affixed. The polyurethane foam provides thermal
insulation to the light-framed wall structure as well as additional
structural reinforcement. By binding to the wall structural
elements the polyurethane foam reinforces those elements from
moving with respect to one another and, as such, provides strength
to the light-framed wall structure. Desirably, the polyurethane
foam extends throughout the stud cavity and covers sheathing on at
least one surface of the wall frame that would otherwise be exposed
within the stud cavity in order to provide thermal insulation, air
and vapor barrier properties and structural reinforcement
throughout the entire stud cavity.
[0038] Polyurethane foam can, but does not necessarily, fill a stud
cavity. Commonly, the thickness of the polyurethane foam is less
than the width of the stud and so there is still void space within
a stud cavity. Moreover, electrical fixtures and wiring, plumbing
pipes and the like can exist within a stud cavity in combination
with the polyurethane foam. Polyurethane foam can be introduced
into stud cavities before or after installation of electrical
components (fixture, wiring, and the like) and/or plumbing
components. Beneficially, the polyurethane foam can expand within
the stud cavity around the electrical and/or plumbing
components.
[0039] The polyurethane foam is desirably a spray-in-place (or
simply "spray") polyurethane foam. Spray polyurethane foam
inherently attaches to wall structural elements (studs, plates and
sheathing) that it contacts as it cures. Application of spray
polyurethane foam to a light-framed wall structure can occur with
the light-framed wall structure in any orientation including a
vertical orientation, such as is typically the orientation in a
completed building structure. Spray polyurethane foam is becoming
common in the construction industry as an insulating material. A
desirable feature of spray polyurethane foam is that it can be
applied to a wall structure on the construction site or any time
prior to arriving at the construction site and to a wall structure
in any orientation. Another desirable feature of spray polyurethane
foam is that it can be applied at a constant or a variable
thickness within a stud cavity. For example, the polyurethane foam
can be applied thicker proximate to the top plate than on average
within a stud cavity in order to provide greater structural
integrity proximate to the top plate. Spray polyurethane foam can
be readily applied thicker proximate to the top plate in order to
achieve such a configuration. Measure polyurethane foam thickness
perpendicular to the sheathing material to which it is affixed.
[0040] Other than spray-in-place polyurethane foams, pour-in-place
polyurethane foams are also suitable, particularly for
prefabricated light-framed wall structures that are made remotely
from the construction site and delivered as a unitary structure to
the construction site. As with spray polyurethane foams,
pour-in-place polyurethane foams inherently tend to adhere to the
building elements they contact as they cure.
[0041] The polyurethane can have an open cell or closed cell
structure, though closed cell foam is generally preferred because
it is often a better thermal insulator and mechanically stronger
foam. Closed cell foam has an open cell content of 30% or less,
preferably 20% or less, more preferably 10% or less, still more
preferably 5% or less and most preferably 1% or less according to
ASTM method D-6226.
[0042] The polyurethane foam desirably has a density of 0.4 pounds
per cubic foot (pcf) or more, preferably 0.5 pcf or more or more
and can be one pcf or more. At the same time, the polyurethane foam
desirably has an expanded density of 2.8 pcf or less, preferably
2.2 pcf or less and can be 2.0 pcf of less. When the polyurethane
foam has an expanded density below 0.4 pcf it provides less than
optimal structural reinforcement to the light-framed wall
structure. When the polyurethane foam expanded density exceeds 2.8
pcf a higher cost and reduction in thermal insulation of the foam
tends to outweigh an enhanced mechanical strength. Generally, open
cell polyurethane foam is lower density foam than closed cell foam.
Open celled foam is commonly available as nominally 0.5 pcf foam
and closed cell foam is commonly available as nominally two pcf
foam.
[0043] Characteristic of the present invention is use of a single
top plate in combination with a stud spacing in a range that is
nominally 16-24 inches on center. Yet the light-framed wall
structure of the present invention surprisingly has the further
characteristics of concomitant unexpectedly high axial point,
lateral and transverse load bearing properties. Light-framed wall
structures of the present invention surprisingly can concomitantly
support: (1) axial point loads of 2500 pounds or more, even 3000
pounds or more according to ASTM method E72, Section 9 as modified
in the Example below (exclusion of the I-beam along the top plate);
(2) lateral loads of 500 pounds per linear foot (plf) or more, even
750 plf or more, and even 1000 plf or more according to ASTM method
E72, Section 14; and (3) transverse loads of 150 pounds per square
foot (psf) or more, even 200 psf or more, and even 250 psf or more
according to ASTM method E72, Section 11.
[0044] Even with a single top plate and stud spacing of a nominal
24 inches on center, and even when using 2.times.4 studs with a
single top plate and stud spacing of a nominal 24 inches on center,
wall structures of the present invention can achieve these
demanding axial point load bearing values without having to
position the axial point load within one inch of a stud, as the
building codes presently specify. Such an achievement is a valuable
advancement in the art by achieving prescribed structural integrity
while reducing the framing factor of a structure. Reducing the
framing factor corresponds to reducing the amount of a structure's
surface area that corresponds to framing (for example, studs, top
plates, and bottom plates). The framing can serve as thermal shorts
through the walls of a building so reducing the framing factor of a
structure allows for reduced thermal shorts through the wall of the
structure.
[0045] These surprising load bearing characteristics make the
light-framed wall structure of the present invention exceptionally
desirable in the building industry because the light-framed wall
structure offers desirably high mechanical integrity with
versatility in placing loads relative to stud positions all while
reducing the number of framing elements relative to common
light-framed wall structure designs. For example, 2.times.4 studs
with a nominal 24 inch spacing and with a single top plate can be
used without requiring roof rafters or floor joints to align within
one inch of the studs of the present invention. Moreover, use of
thermally insulating exterior sheathing provides efficient
thermally insulating properties and reduces or minimizes thermal
shorts through the light-framed wall structure caused by studs.
[0046] Another aspect of the present invention is a process for
making the light-framed wall structure of the present invention.
The process comprises assembling studs nominally spaced 24 inches
on center between a single top plate and a bottom plate so as to
form a wall frame that defines stud cavities between the studs and
the top and bottom plates and affixing the studs to the top and
bottom plates; affixing a sheathing onto a surface of the wall from
over the studs and stud cavities; and disposing a polyurethane foam
into the stud cavity onto the exterior sheathing and against the
studs and top and bottom plates so as to have an average expanded
thickness of at least two inches within the stud cavity and so that
the polyurethane foam attaches to the sheathing, studs and top and
bottom plates of the stud cavity. The process can include applying
and affixing sheathing to both the exterior and the interior
surfaces of the wall frame. Each of the building elements and
various embodiments of the elements and structures for use in the
process of the present invention are as described for the wall
structure of the present invention.
[0047] Yet another aspect of the present invention is a building
structure comprising the light-framed wall structure of the present
invention. The light-framed wall structure of the present invention
has utility as a wall for a building structure. A building
structure comprising the light-framed wall structure of the present
invention is not possible apart from the light-framed wall
structure of the present invention. Therefore, the building
structure comprising the light-framed wall structure of the present
invention is yet another embodiment of the present invention.
[0048] The following Example serves to illustrate an embodiment of
the present invention. Notably, transverse load values were not
actually measured but are expected to exceed 200 psf based on prior
testing of similar structures with fewer components.
EXAMPLE 1
Absent Interior Sheathing
[0049] FIG. 1 illustrates two different views of light-framed wall
structure 10 of the present invention and Example in order to
further facilitate understanding of the present invention.
[0050] Position two 2.times.4 dimensional lumber studs 20 that are
93 inches long between single 2.times.4 dimensional lumber top
plate 30 and single 2.times.4 dimensional lumber bottom plate 40
and spaced apart a nominal 24 inches on center. The 2.times.4
dimension lumber is 1.5 inches thick and 3.5 inches wide. Fasten
studs 20 to the both top plate 30 and bottom plate 40 by using two
3.5 inch long 0.162 inch diameter nails per stud to form an wall
frame defining a stud cavity with one 3.5 inch wide surface from
each of studs 20 and plates 30 and 40 facing the cavity. Attach to
the wall frame exterior sheathing 50, a sheet of 0.5-inch thick
STYROFOAM SIS.TM. Brand Structural Insulated Sheathing, so as to
cover the stud cavity from one side of the wall frame. Attach
sheathing 50 to the wall frame using 7/16-inch crown by two-inch
long 16 gauge staples.
[0051] Spray polyurethane foam 60 (for example, Dow Spray Foam
2045, available from The Dow Chemical Company) into the stud cavity
to an expanded thickness of at least two inches. Over the area
within 6 inches of top plate 30 spray polyurethane foam 60 to an
expanded thickness of 3.5 inches. Cover any of sheathing 50
otherwise exposed in the stud cavity with spray foam 60 and dispose
spray foam 60 against studs 20 and plates 30 and 40 around the
perimeter of the stud cavity. Spray foam 60 expands to an average
density of 2.2 pcf.
[0052] Test the resulting light-framed wall structure 10 to a
lateral load wall strength test (ASTM E72, Section 14) and a
modified axial point load wall strength test (ASTM E72, Section 9).
Modify the axial point load wall strength test by excluding the
I-beam spanning the stud cavity over top plate 30. In other words,
apply the axial point load directly onto top plate 30 centrally
between studs 20. This modification makes it more difficult for
light-framed wall structure 10 to support axial point loads because
the I-beam is not present to help distribute the load. Nonetheless,
light-framed wall structure 10 performs remarkably well in each of
the lateral load wall strength test, transverse load test and the
modified axial point load wall strength test.
[0053] The Example light-framed wall structure 10 withstands
lateral loads up to 1081 plf. For reference, a comparative code
compliant light-framed wall structure with 2.times.4 studs 16
inches on center and using a double top plate with fiberglass
insulation in the stud cavity and wood structural panel sheathing
fasten with 0.113 shank diameter nails and 6 inches on center at
the edges and 12 inches on center on non-edge studs, and covering
the exterior surface of the wall frame only bears up to 515 plf in
the lateral load test.
[0054] The Example wall structure 10 withstands axial point load up
to 3294 pounds in the modified axial point load wall strength
test.
[0055] This Example illustrates a light-framed wall structure of
the present invention that can support remarkably high lateral,
axial point and transverse loads despite having a single top plate
and 2.times.4 studs positioned a nominal 24 inches on center.
[0056] The performance of wall structure 10 would only improve
(that is, load values would stay the same or increase) with the
inclusion of interior sheathing. Hence, the surprising result of
the strength of this wall is independent of the type of interior
sheathing that one might include to bring this example within scope
of the present invention.
EXAMPLE 2
One-Inch SIS Exterior Sheathing
[0057] Prepare a wall structure similar to wall structure 10 of
Example 1 except use a one-inch thick SIS panel for the exterior
sheathing 50 and a spray polyurethane foam to a thickness of at
least one-and-one half inches in the stud cavity while having an
expanded thickness of 3.5 inches entirely within ten inches (which
inherently includes the first six inches) of top plate 30. Attach
an interior sheathing to the wall frame on an opposite side to the
SIS exterior sheathing so as to cover the stud cavity from the
inside of the wall frame. Use as interior sheathing 0.5-inch thick
gypsum wall board using number 6 screws every sixteen inches around
the perimeter and interior of the board.
[0058] Test the resulting light-framed wall structure in like
manner as the first example except use unrestrained ASTM E-2126 for
testing lateral load wall strength. The "unrestrained" test format
means that the wall is only anchored to a test base with 1/2-inch
anchor bolts every six feet and not restrained with other
hold-downs or tie down rods. The resulting wall structure has a
capacity of 759 pounds per lineal foot under the lateral load test
and 4031 pounds in the axial load wall test.
EXAMPLE 3
Wood Exterior Sheathing
[0059] Prepare a wall structure similar to wall structure 10 in
Example 1 except use as the exterior sheathing 7/16-inch thick
grade PS2 24/0 oriented strand board. Test the resulting
light-framed wall structure in like manner as wall structure 10 in
Example 1.
[0060] The resulting wall structure has a capacity of 1422 pounds
per lineal foot under the lateral load test; an excess of 200 psf
in the transverse load test and 7348 pounds in the axial load wall
test. As with Example 1, addition of interior sheathing would not
diminish these values and so including any interior sheathing to
the structure of this example would have at least these
surprisingly high capacity values.
EXAMPLE 4
Gypsum Board Sheathing
[0061] Prepare a wall structure similar to wall structure 10 in
Example 1 except use as the sheathing 1/2-inch thick standard
interior gypsum board. Test the resulting light-framed wall
structure in like manner as the wall structure in Example 2.
[0062] The resulting wall structure has a capacity of 678 pounds
per lineal foot under the lateral load test and 4262 pounds in the
axial load wall test. Test results are expected to stay the same or
increase if another sheathing was included on an opposing side of
the wall structure.
EXAMPLE 5
Extruded Polystyrene Foam Sheathing
[0063] Prepare a wall structure similar to wall structure in
Example 2 except use as the exterior sheathing one-inch thick
extruded polystyrene foam (STYROFOAM.TM. Residential Sheathing,
STYROFOAM is a trademark of The Dow Chemical Company). Test the
resulting wall structure in like manner as the wall structure in
Example 2.
[0064] The resulting wall structure has a capacity of 490 pounds
per lineal foot under the lateral load test; an excess of 200 psf
in the transverse load test and 3494 pounds in the axial load wall
test.
EXAMPLE 6
Structure with Polyurethane Fillet Picture Framing
[0065] Prepare a wall structure similar to the wall structure in
Example 2 except deposit the spray polyurethane foam as a
triangular shaped bead around the inside perimeter of the stud
cavity and in the top ten inches (as measured from the top plate)
of the stud cavity. The spray polyurethane triangular cross section
bead measures 1.5 inches by 1.5 inches at the legs of the triangle,
with one leg extending over the sheathing and the other leg
extending over a stud, top plate or bottom plate. The volume of the
stud cavity within ten inches of the top plate is filled to an
expanded depth of 3.5 inches of polyurethane foam.
[0066] FIG. 2 illustrates a view of the Example 7 wall structure
without the interior sheathing and viewing from the interior side
of the wall structure. Wall structure 10 comprises 2.times.4
dimensional lumber studs 20 that are 93 inches long between single
2.times.4 dimensional lumber top plate 30 and single 2.times.4
dimensional lumber bottom plate 40 and spaced apart a nominal 24
inches on center. The 2.times.4 dimensional lumber is 1.5 inches
thick and 3.5 inches wide. Exterior sheathing 50 is a sheet of
one-inch thick STYROFOAM SIS.TM. Brand Structural Insulated
Sheathing. Spray polyurethane foam 60 extends around the interior
perimeter of the cavity and fills the top ten inches within the
cavity.
[0067] Test the wall structure in like manner as Example 2. The
resulting wall structure has a capacity of 699 pounds per lineal
foot under the lateral load test, and (though not tested) is
expected to achieve at least 4031 pounds in the axial load wall
test due to the similarity of the structure to that in Example
2.
* * * * *