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BACKGROUND OF THE INVENTION
This invention relates generally to a method for constructing a house or
similar building using tilt-wall concrete panels, more particularly, it
relates to a method of creating a high-strength, thin, thermally efficient
concrete/foam panel by use of a reduced number of auxiliary devices,
frames or molding elements.
It is well known to construct buildings for use as offices, warehouses,
factories, stores and the like by the use of tilt-wall concrete
construction techniques which are exemplified in the teachings of patents
such as US Pat. No. 4,104,356 to Deutsch and Jones entitled "Tilt-Up Panel
Bracket" and U.S. Pat. No. 3,555,763 to Bloxom entitled "Method of Forming
Walls with Prefabricated Panels." However, the concrete walls created by
these conventional building techniques have their greatest utility in what
may best be described as commercial buildings, for the reason that the
interior surfaces of such concrete walls are not considered suitable for
sophisticated buyers of residential properties. That is, builders of
residential properties recognize that conventional wood studs need to be
added to the insides of concrete walls in order to provide space for
insulation and utility conduits, as well as to provide an anchor into
which nails may be driven when installing conventional interior paneling
materials such as gypsum board (or sheet rock) or wood paneling. The
expense and time of installing wood or metal studs to an existing concrete
wall has meant that traditional tilt-wall construction techniques have
generally not been considered economically feasible for residential
construction.
In an attempt to obviate the economic disadvantage of attaching studs to a
standing concrete wall, US Pat. No. 4,059,939 to Eilliott entitled
"Prefabricated Building Unit" teaches the concept of casting concrete on
top of a completed wooden frame of traditional size and strength, and
ensuring a mechanical connection between the wooden panel and the hardened
concrete by virtue of providing numerous long nails that protrude upwardly
from the wooden studs into the cavity that is to be filled with wet
concrete. Additionally, Elliott teaches the inclusion of prefabricated
insulation boards between the concrete and the wooden studs, such that a
three-quarter inch insulation board (for example) is captured between the
hardened concrete and the interior wooden frame. While the teachings of
Elliott might seem to go a long way toward meeting some of the objections
of tradition tilt-wall techniques as they are applied to commercial
buildings, there are still certain difficulties in adapting tilt-wall
concepts to residential construction. For example, Elliott teaches that
his concrete and wooden panels are best fabricated in a factory and then
lifted by a crane onto a truck for transportation to a construction site.
A crane would then be employed to remove a panel from the truck and lower
it onto a prepared foundation. Such a process has several disadvantages,
including the fact that a crane must be employed to first load the panel
on a truck at the site where the panel is fabricated, and a crane is also
required at the construction site where the house is to be built. This
either requires the use of two cranes or the movement of one crane (a
large and sometimes awkward piece of mechanical equipment) from a factory
and along public streets to a residential building area. Furthermore, the
Elliott process appears to offer no savings in materials as compared with
previously known techniques for attaching wooden frames to the interior of
a tilt-wall building. There has therefore remained a need for an
economical and efficient technique for constructing houses and similar
buildings in which the advantages of tilt-wall construction can be
exploited in the fabrication of residential buildings asnd the like. It is
an object of this invention to provide such a technique.
Another object is to provide a construction technique for standardizing the
installation of utility conduits and the like by positioning them in a
highly controlled environment such as a factory, rather than leaving their
installation to the discretion or judgment of workers at a remote
construction site.
Still another object is to provide an improved building panel for
residential construction techniques in which a relatively thin wall panel
thickness is achieved without any degradation of thermal efficiency.
A further object is to provide a relatively strong but economical and
attractive building, using materials that are likely to be readily
available in most developed areas.
These and other objects will be apparent from a reading of the
specification and the claims appended thereto, with reference to the
accompanying drawings forming a part hereof.
DESCRIPTION OF THE FIGURES OF THE DRAWING
FIG. 1 is a perspective view of a frame positioned horizontally on top of a
work surface, showing certain components of the panel prior to the time
that an insulating plastic foam is generated.
FIG. 2 is a perspective view of the same panel that is shown in FIG. 1,
which now has been rotated approximately 90 degrees clockwise, with a
fragmentary portion of the plastic foam being shown where it has been
generated on top of the frame and its stud-like members.
FIG. 3 is a fragmentary cross-sectional view taken in the plane represented
by lines 3--3 in FIG. 1.
FIG. 4 is a fragmentary cross-sectional view taken in the the plane
represented by lines 4--4 in FIG. 2.
FIG. 5 is a fragmentary, cross-sectional view of a left-hand corner of a
peripheral form, just prior to the time that concrete is poured into the
form and on top of the plastic foam.
FIG. 6 is a fragmentary view of the top right-hand corner of a completed
concrete/foam panel, with the top board (or header board) being removed to
show the relative positions of the main constituents of a panel.
FIG. 7 is a fragmentary, cross-sectional view of the bottom of a completed
panel, showing the relative position of the horizontal foot and a
representative vertical stud-like member.
FIG. 8 is a perspective view of a completed concrete/foam panel after it
has been tilted upward and is ready for installation as a part of a
building.
FIG. 9 is perspective view of a concrete form having two planar segments
(or "plates") positioned therein, prior to the time that concrete is
poured over the segments.
FIG. 10 is a perspective view of a multi-story panel in accordance with
this invention, wherein two planar segments are exposed on the interior
face of the panel at two different elevations.
BRIEF DESCRIPTION OF THE INVENTION
In brief, the invention encompasses a method of fabricating a tiltwall
concrete/foam panel; one embodiment is particularly adapted for
constructing a building such as a single-family residence. Each panel has
an exterior of cementitious material and a smooth interior with readily
accessible studs of wood or the like. Initially, a generally horizontal
and flat work surface is established in a factory or some other convenient
working area. The size of the work surface must be somewhat larger than
the size of the largest panel that is to be fabricated, so that a
peripheral frame of wooden members (e.g., 2.times.4 inch boards) may be
laid on top of the work surface. The work surface is covered with a
barrier film of non-adherent plastic such as 4 mil polyethylene, and the
peripheral frame is laid on top of the film. A plurality of wood-like
studs are then positioned within the frame and secured thereto in such a
way that they lie on top of the polyethylene film (which will define the
interior face of the concrete/ foam panel when it is completed). Next, any
desired utility cables, boxes, conduits, wires and the like are placed
within the boundary defined by the frame and secured typically with
light-duty fasteners, so that they are fixed in position and will not be
accidentally moved during a subsequent step. An insulating foam cover is
then generated in situ within the frame to a depth so as to at least cover
the wood-like studs--and usually any utility cables, etc. High density
polyurethane foam (in the range of 11/2 to 4 pounds per cubic foot) is the
preferred material for this part of the panel. A foam thickness of about
11/2 inches will usually be adequate for a concrete/foam panel which is
intended to serve as the exterior wall for a typical single-family
residence; but the foam will generally be only about 1/2inch thich over
the wood-like studs, in order to leave adequate room for the concrete is
to be cast on top of the foam. After the foam has cured, the frame is
ready to be transported to a site where the building is to be erected and
where a foundation has already been prepared or is being prepared.
The frame and foam "plate" (or planar segment) is positioned "face down" on
top of the smooth foundation, and a concrete form is created by placing
boards (typically 2.times.6 inch boards) around said "plate". Wet concrete
is then poured into the 2.times.6 frame, usually to the full depth
thereof-- which is actually about 5 1/2 inches. After the concrete has
set, the resulting structure--which may now be properly described as a
concrete/foam composite panel-- is tilted upright at an appropriate
location on the foundation, typically at one edge thereof. Any unwanted
members of the concrete frame are removed from the composite panel, and
the polyethylene film is pulled away from its face. When the panel is
being used in a single-story building, the top of the concrete form will
usually be left with the composite panel to form a permanent part thereof;
the roof structure is then nailed to the top piece. For some multi-story
buildings, the top as well as the sides and the bottom of the form may be
removed after the concrete has cured. Other composite panels, each with
its own quantity and arrangement of windows, doors, utility outlets, etc.,
are similarly built. Adjacent concrete and foam plastic panels are
connected to one another at their respective edges (sides), and the bases
of the panels are anchored to the foundation--with bolts or other
fasteners, or with welding. Gypsum board (or sheet rock) or other interior
paneling is then readily nailed to the wood-like studs, and the protruding
ends of the electrical cables at the tops of the composite panels are then
connected to appropriate fixtures, switches, and utility outlets in the
same way that electrical wiring is routinely connected in a custom-built
building, etc. Any gaps between adjacent panels are caulked or otherwise
filled with a resilient material, and the exterior concrete surface is
finished in a customery manner.
DETAILED DESCRIPTION OF ONE EMBODIMENT OF THE INVENTION FOR BUILDING
SINGLE-FAMILY RESIDENCES AND THE THE LIKE
Turning first to FIGS. 1 and 2, a generally horizontal work surface 10 is
established at a convenient location which is preferably dry, clean and
well illuminated. Such a surface 10 is preferably prepared in a factory,
workshop or other secure location where careful and measured work may be
safely performed with automatic and semi-automatic tools and equipment,
including air-powered nailers, staplers, etc. One reason for selecting a
factory-type work area for this early step in the process of fabricating a
panel is to avoid the interruptions which can be caused by inclement
weather (including rain, snow, high winds, etc.) as well as avoiding the
risk of loss or theft of building materials at a remote construction site.
Additionally, completing the early phases of panel construction in a
factory environment makes it possible to more nearly ensure quality
control in implementing the design decisions that have been made with
regard to the number and location of utility outlets and service conduits,
etc. In other words, it is easier to supervise the construction of a
variety of panels when they are at least partially pre-fabricated in a
concentrated work area instead of being individually created at varied and
remote locations. Also, construction materials may be kept cleaner and
protected from accidental damage when they are stored in a covered
environment until such time as an individual panel is to be built.
A typical flat and smooth work surface 10 is advantageously a large frame
of steel that is covered with plywood, approximately 25 feet long and 9
feet wide. A work surface this size will usually provide sufficient space
and clearance for pre-fabricating a planar segment of almost the same
size, which should be adequate to take care of essentially all
requirements for building panels for single-family residences and similar
small buildings. A plywood work surface 10 does not constitute a heat sink
for the warm foaming plastic, and it can also provide a base to which
clamps may be easily attached for temporarily holding framing boards in
place.
On top of the work surface 10 is temporarily placed a non-adherent film 12,
which may advantageously be a sheet of polyethylene plastic approximately
4 mils thick. The purpose of the film is to serve as a barrier between the
work surface 10 and the plastic foam which will be generated in situ and
which will constitute most of the interior face of the finished plate. The
integrity of the film 12 is important but not critical, because it can be
patched with simple patching techniques (including something as simple as
duct tape) if a small tear is discovered. This is advantageous because of
its simplicity and, indeed, the entire process disclosed herein is
characterized by simplicty, economy and reliability. Expressed in other
words, there are no parts of this construction method which employ
unusually precise tolerances or exotic materials that might dictate the
use of highly skilled and/or expensive labor. In fact, if polyethylene
film or its equivalent is not available, the work surface 10 may even be
coated with an ordinary releasing agent, so that the foamed plastic that
is generated on top of the work surface will not adhere thereto.
The next step in the process involves creating a peripheral frame 14 for
the panel--on top of the work surface. Typically the peripheral frame 14
is formed by nailing together four members: a top 16, a right side 18, a
left side 20 and a bottom 22. Ideal frame members are boards having a
nominal size of 2.times.3 inches, 2.times.4 inches and 2.times.6 inches,
or similarly sized aluminum channels, which are widely available and have
the requisite strength to function as an open frame for building a large
panel. The frame 14 is laid out on the work surface 10 and all angles are
carefully checked to make sure that they are 90 degrees, etc; temporary
clamps are advantageously affixed to the work surface to ensure that the
frame remains true during this phase of the fabrication process.
Next, a plurality of wood-like studs 24 are positioned interiorly of the
open frame 14 and arranged, side to side, using distances that will
usually be larger than the spacing for conventional wall studs in what
some persons refer to as "stick and brick" residences. Thus, the wood-like
studs 24 will usually be about 24 inches apart, but they need not be of
the same material or size as conventional wood studs (which are typically
2.times.4 inch white pine or fir). This is because the rib-like members 24
in accordance with this construction do not need to have an inherent
strength and rigidity in order to remain vertical and transfer loads in
the way that conventional wall studs do. Instead, the members 24 in this
construction serve primarily as anchoring spots for the nails, screws,
staples or other fasteners that will be subsequently utilized to affix an
interior covering to the inner face of a completed panel. Additionally,
the materials from which stud members 24 are fabricated will likely be
wood; but other materials-such as metal or closed-cell foamed
plastics--are known to be appropraite substitutes for wood when either
price or environmental conditions might make a substitute desirable. So,
in an area where wood is scarce or expensive, or is subject to rapid
attack by termites, etc., a wood-like material (including its equivalent
in metal) could be readily substituted for the normally preferred wooden
studs 24. These studs 24 are usually anchored at their ends to the open
frame 14 by driving one or more nails transversely through the top 16 and
the bottom 22 of the frame.
Edge members 18, 20 are also nailed to the top and bottom pieces of the
frame 14. These edge members 18, 20 are typically 2.times.4 inch boards,
oriented with their long sides flat against the film 12, which means that
they will subsequently provide a significant surface area into which a
connector for two adjacent panels might be anchored.
The next step involves placing within the peripheral frame 14 may utility
devices, wires, vent pipes and the like which will be desired in the
eventual panel. For example, if an electrical outlet or a light switch is
wanted in a given panel, provision for it must be made at this time. For
an electrical service outlet, an electrical box 26 will be tacked to the
side of one of the stud members 24 at the appropriate location and with
its open face toward the film 12. Appropriate conduits or wires 28 (of a
size and nature to satisfy any pertinent building codes) would then be
placed inside the frame 14, so that one end of the conduit extends into
the box 26; the other end of the conduit passes through a prepared
aperture in the top member 16 and extends outside the frame. Any other
electrical, telephone, television, water or gas service which is desired
in an exterior wall would be accomplished by positioning the appropriate
pipes, conduits, wires, etc., in accordance with plans that had been
established by the builder.
After all utility connections and the like have been established within the
frame 14, usually adjacent the film-side thereof, a foamed plastic 30 is
next produced within the frame by placing therein a foaming plastic in
liquid form; said liquid is caused to foam until it produces a foamed body
having a depth which is at least adequate to cover the plurality of
woodlike studs 24 and probably most of the peripheral members 18, 20, 22,
as well as many of the utility elements (e.g., any Romex cables, etc.). If
the foam body 30 is made of inherently closed-cell foaming material, then
waiting a few seconds for the foam to set will produce a water-impervious
top skin that will automatically complete this face-producing step. On the
other hand, if the plastic foam is initially open-celled, it will be
necessary to subsequently seal its top in order to produce a body that can
function as the bottom of a mold for eventually receiving wet concrete.
The preferred material for this insulating body 30 is a polyurethane foam
having an integral skin and a minimum density of 1 pound per cubic foot;
to further ensure the requisite holding strength, a density of 11/2 pounds
per cubic foot is preferred as the "low side" value. A density in excess
of 4 pounds per cubic foot is probably not cost effective, for the reason
that any extra strength is probably not worth the extra expense.
Therefore, the preferred range of densities can be said to be between 11/2
and 4 pounds per cubic foot. A suitable foaming material is sold by
Carpenter Insulating and Coatings Company (having an office in Dallas,
Texas) under their notation 275-B class II polyurethane resin. In general,
it is expected that foam body 30 will be approximately 11/2 inches thick
in regions between any two adjacent studs 24, and about 1/2 inch thick in
regions immediately over the studs, as represented in FIG. 4. In other
words, it is believed desirable to have at least 1/2 inch of polyurethane
insulating material between any interior studs and the exterior concrete.
In a very short time the preferred urethane foam will have cured so that it
creates a rigid side-to-side and top-to-bottom structural component which
secures the studs 24 in an immovable position in the frame 14; the foam
also supports any utility devices in the exact location they were in
before the foam was generated. If the selected foam is high-density
polyurethane, the excellent adhesion between the foamed plastic and the
frame members 16, 18, 20, 22 as well as the adhesion between the plastic
and studs 24, will produce an exceedingly strong "plate" 32 for the bottom
of a mold or form into which concrete may be subsequently poured at will.
Indeed, the combined strength of the frame 14 and the integrally foamed
plastic 30 is sufficient that the plate 32 can be readily transported for
substantial distances to a building construction site without any concern
that the plate will warp or become skewed during normal handling.
While the plate or planar segment 32 is very strong, it is not exceedingly
heavy; and it is common to simply utilize a few strong laborers to
manually lift the plate off the work surface 10 and place it on the bed of
an adjacent truck or trailer. A typical plate 32 about 20 feet long and
slightly more than 8 feet high, with the preferred 2.times.2 inch studs 24
and polyurethane foam at about three pounds per cubic foot, will weight
about 150 pounds, which can be manually handled without too much trouble
by three or four workers. The plate 32 is also relatively thin; and even
if a 2.times.6 inch header board is attached to the top of the frame 14 in
the factory, two such plates can be placed face to face (with the header
boards sticking out over the edge of the truck bed) and take up very
little vertical space.
Before the plate 32 is removed from the preferred (i.e., clean, dry,
factory-type) fabrication site, it will probably be appropriate to take
advantage of the powered equipment that is normally available in such a
facility. For example, it is advantageous to drill at least one hole (and
usually two) transversely through the top member 16, and then slightly
elongate the hole to create a generally slot-like opening 40 almost 1 inch
long. At the building construction site, a piece of steel cable (about
.cuberoot. inch in diameter) is advantageously formed into a loop 42, and
the two ends of the cable are passed through the slot 40 (from the outside
to the inside). The two ends of the cable are then positioned so that they
will be securely imbedded within the concrete that is poured on top of the
plastic foam 30. When the concrete has cured, the externally protruding
loop 42, either alone or in combination with another loop, can be
connected through a cable to a crane, so that the composite panel can be
easily tilted upward at one edge of the foundation.
After all of the plates 32 have been transported to the prepared foundation
site for the building, they are laid "face down" on top of the foundation.
A concrete form is then created by affixing a peripheral frame of wooden
members, typically 2.times.6 inch boards, around the plate 32; aluminum
forms are also useful for this function, and they are relatively easy to
keep clean and are re-usable. Before wet concrete is poured into the form
33 (represented by the two wooden members 37, 38) shown in FIG. 5, it is
advantageous to drive a few nails transversly through the top member 16
into the space immediately above foam member 30. Other nails 35 may be
driven from the back side of the plast 32 into the frame members 18, 20
and the wood-like studs 24; at least part of their length is left
protruding upwardly into open space. These protruding nails will then be
firmly anchored in the concrete that subsequently fills the wide, shallow
cavity that is defined by the peripheral form 33 and the plate 32. As with
any substantial concrete structure, it will likely be advantageous to
provide reinforcing rods or wire mesh (represented by members 34 in FIG.
5) in the space that is to be filled with concrete. Plastic chairs,
indicated by the device 36, can be used at this time to hold the wire mesh
34 in an elevated position so that it will eventually be completely
surrounded by concrete.
After concrete 44 has been poured into the form 33 and allowed to set--to
produce a plurality of concrete/foam composite panels 50, the sides and
bottom of the form are removed by prying them away from the panel. Any
window or door framing members that are not necessary for anchoring their
respective windows or doors are also removed at this time. A crane or
similar piece of lifting equipment is then utilized to tilt the panels 50
upward until they are vertical. Usually a first panel 50 will be
permanently connectd to the foundation, and adjacent panels will then be
serially connected, first to the foundation and then to each other, so as
to completely enclose what is to become the interior of the building. Any
existing gaps between adjacent panels 50 are filled with caulking and/or a
resiliant joint material. A roof is then added to the building in a
traditional manner, and the building is then ready to have its windows and
doors installed so that it is completely "in the dry". (It is relatively
easy to install roof trusses without causing interference with the cable
loops 42, so they may be simply left in place on top of the panel 50.) At
this time it is appropriate to provide a protective cover over the inside
of the panels, to more nearly ensure that the polyurethane foam 30 (which
is exposed after the protective film 12 has been peeled away) is less
vulnerable to any interior fire. Traditional gypsum board having a
thickness of 1/2 inch is the preferred interior cover for the wall panels,
because of its insulating qualities and its ability to be cosmetically
finished in a variety of pleasing ways.
The exterior of the wall panels 50 may be attractively finished with a
stucco medium; or, one of the very thin decorative brick materials may be
employed to give the building the appearance of a brick veneer house
without the expense or structural deficiencies of such a construction.
Other ways of decorating the exterior of the panels may, of course, be
readily apparent to those skilled in the art, so that the resultant
building may take on essentially any desired appearance. This is
particularly appealing because the economies that accure to the builder
from this construction technique are not in any way apparent in the
external appearance of the completed building. In other words, while this
invention may be produced more economically than many custom-made houses,
it need not have the appearance of being built on a modest budget.
While a single-family residence made in accordance with this disclosure may
look the same as many prior art houses, it will actually be much stronger
than conventional wood-frame houses. In fact, exterior walls made with
panels created by solidly filling 2.times.6 inch framing boards with 3000
psi concrete will be expected to have a loading strength of 50 pounds per
square foot, while many conventional houses are only rated at about 20
pounds per square foot. In addition to overall strength, a wall made in
accordance with this invention using nominally sized 2.times.6 board as
concrete form members will have an average insulating value of R-11.
DETAILED DESCRIPTION OF AN EMBODIMENT OF THE INVENTION FOR MULTI-STORED
BUILDINGS
The disclosure to this point has dealt primarily with concrete/foam panels
intended for use in single-story buildings, but it would be entirely
feasible to utilize the same principles in constructing multi-story
buildings. For two-story or higher buildings, however, narrower panels
would probably be employed--in order to limit their total weight and
facilitate tilting them to an upright position. Referring next to FIG. 9,
a planar segment 32A will be prepared for each floor of a multi-story
building that is to have a cosmetically-finished interior. That is, if
both the first and second floors of a two-story building are to have rooms
which are finished out with gypsum board or the like, then two segments
32A will be pre-fabricated and brought to a construction site where a
foundation has been prepared. The front surface of the respective planar
segments will be oriented downward and the segments laid on top of the
foundation. A separation distance will be established between the two
segments, which distance is equal to the height of the anticipated
structural support for the second floor. A concrete form of aluminum or
wooden members will then be established around the planar segments, and
concrete will then be poured into the form and on top of the segments. The
concrete will be allowed to cure in direct contact with the rear surface
of the planar segments 32A so as to form a composite concrete/foam panel.
The peripheral frame members will, of course, be removed from the
concrete/foam panels after the concrete has cured. Appropriate lifting
cables will then be affixed to the "top" end of the panel, and probably at
least one intermediate point thereof, and the panel will then be tilted
upward so that it is essentially vertical (FIG. 10). As before, each
tilted panel will be connected to the foundation and to such adjacent
panels as are appropriate for completing the exterior part of the desired
building. Floor joists would then be mechanically connected in a customary
manner to the inside of the panel (between the two planar segments), and
any desired cosmetic and/or protective covers would be fastened to the
front surface of the respective segments.
To review the essential parts of the method disclosed herein, and to recite
certain optional steps, a condensed listing of the important facets of the
invention will now be presented, in an approximately sequential manner:
Prepare plans for the building and decide on the location of utilities for
exterior walls.
Establish a generally horizontal and flat work surface.
Cover the work surface with a non-adherent film or separating agent.
Create on the work surface a peripheral frame for the first one of several
panels.
Position wood-like interior members (e.g., wall studs) and secure them
within the frame.
Position utility wires, conduits, boxes, pipes, etc., within the frame,
usually adjacent the appropriate interior members.
If the finished panel is to have a window or door, position a suitable
inner frame for said window or door inside the peripheral frame.
Generate an insulating foam inside the peripheral frame and on top of the
film to a depth so as to cover the interior members and at least most of
each of the peripheral frame members.
Allow the foam to cure so as to rigidly lock all elements in place within
the peripheral frame, thereby creating a plate-like element that will
become a layer or segment of the eventual panel.
If the foam is an open-cell plastic, seal the top of the foam so as to
provide a water-proof surface for supporting wet concrete.
In a like manner, produce any additional plate-like segments that will be
required for a given building.
Transport the finished segments to the building site where a foundation has
been prepared.
Place each panel segment on a generally horizontal surface with its
"interior side" down.
Place concrete form members around the plate-like segments.
Drive a few "anchor" nails through the foam and into the back side of some
of the wood-like interior members.
Drive any additional "anchor" nails into certain frame members, as deemed
desirable, if those frame members are to remain as a permanent part of the
panel and if enhanced locking between the frame members and the concrete
is desired.
Position any desired wire mesh or | | |
