Note: Descriptions are shown in the official language in which they were submitted.
1176856
EARTH-SHELTERED STRUCTURE
Technical Field
This invention relates generally to earth-
sheltered structures.
Background Art
Throughout his known history, man has used a
variety of mediums from which to fabricate his shelter,
including earth. An increasing awareness of energy usage
~nd waste has inspired a resurge of interest in earth-
sheltered structures. As used herein, "earth-sheltered"
refers not only to underground housing, but also to
structures built above ground that have at least the roof
and one side substantially sheltered by a layer of earth.
Constructing an earth-sheltered structure
requires the builder to take into consideration cert~in
factors not usually present in ordinary construction.
The layer of earth used to shelter and insulate the
structure not only increases the ordinary stress that the
structure must withstand, but also introduces significant
stresses from directions not ordinarily encountered when
; building a non-earth-sheltered structure. ~ecause of
this, the builder should not simply strengthen an ordinary
above-ground structure and assume that it will serve
suitably as an earth-sheltered structure.
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To meet these considerations, the construc-
tion industry has generally relied upon concrete foun-
dation walls to support earth-sheltered structures.
Although such foundations have proven to be structur-
ally sound, they present other problems for the builder.Most importantly, perhaps, such foundations are re-
latively expensive and time-consuming to build and
generally require a significant amount of on-site
preparation and expertise. Concrete foundations also
contribute to an undesirable humid atmosphere in the
structure.
The remaining structural members that con-
tribute towards supporting the structure in earth-
sheltered structures of the prior art include other
important non-wood elements as well. For instance,
metal beams, metal strapping and fiberglass sheer walls
have all been relied upon in various earth-sheltered
structures to assist in supporting both the structure
and the layer of earth. Unfortunately, such items may
be difficult to obtain at times, and may otherwise
necessitate inconvenience in their obtainment and
installation.
There therefore exists a need for a struc-
turally sound, low cost earth-sheltered structure that
may be easily and quickly erected with a minimum of
on-site expertise.
Summary of the Invention
The instant invention meets these needs by
providing an earth-sheltered structure that makes use
of a wood foundation wall. The invention also provides
for a unique ceiling-to-wall juncture made substantially
of wooden members that promote stability and cooperates
with the forces exerted by the sheltering earth to aid
in stabilizing the structure. Significantly, the
supporting members of the structure disclosed herein
are made entirely of wood, with the exception of fasten-
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agents utilized to attach the various members together.
Wood foundations, while not necessarilyunique in the construction art, have not been previously
used in earth-sheltered structures. The construction
industry has not believed that such a foundation would
provide suitable support when used in such an applica-
tion. The applicant has determined that contra this
belief, such foundations can meet and exceed all the
requirements of an earth-sheltered structure.
The ceiling-to-wall juncture also contributes
to the ability of this structure to withstand the
increased stress typically found in an earth-sheltered
structure. This juncture includes a notched ceiling
joist that fits snugly about one or more top plate
members located atop the exterior walls. The notched
fitting forces the supporting members to cooperate such
that the construction materials themselves support the
structure, and not just the fastener items that might
ordinarily be relied upon in an ordinary structure.
Brief Description of Drawin~s
These and other advantages of the disclosed
invention will be made more clear in the following
detailed description of the best mode for carrying
out the invention, and particularly when reviewed in
conjunction with the appended drawings, wherein:
Fig. 1 is a side elevational sectional view
of the structural framework for an earth-sheltered
structure built in accordance with the invention;
Fig. 2 is a front elevational partially cut-
away view of an exterior wall segment;
Fig. 3 is an enlarged perspective exploded
view of the ceiling-to-wall juncture; and
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Fig. 4 is a perspective view of the ceiling-
to-wall juncture.
Best Mode For Carrying Out The Invention
Although the invention disclosed herein could
be applied in a structure built entirely underground,
the applicant intends generally to apply the invention
to structures built substantially above ground and that
are sheltered in a layer of dirt covering substantially
three sides and the roof. Generally, the fourth side
facing south will be left substantially unobstructed
by dirt such that entrances, windows, building facades
and the like may be used.
With reference to Fig. 1, in building a struc-
ture in accordance with the invention, the applicant
first grades the construction site (11) by any manner
and according to such standards as are well-known in
the art. The applicant then covers the construction
site (11) with a layer of gravel or crushed rock (12)
approximately 4 to 8 inches thick. (As used herein,
gravel means gravel having little or no fines.) Addi-
tional support may be gained by providing an additional
thickness of rock approximately 12 inches thick by 24
inches wide (assuming firm soil) or a concrete plate at
those places where the structure will be directly sup-
ported, such as where a wall will be placed (13). Thisgravel footing will distribute the weight of the struc-
ture and of the sheltering earth more evenly over the
supporting construction site (11).
A foundation wall (14) constructed substan-
tially of wood will then be built on top of the gravelfooting (12). In general, this wooden foundation wall
(14) may be constructed in accordance with usual in-
dustry guidelines and standards for wooden foundations
as used in non-earth-sheltered structures, with the
notable exception that structural members will generally
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be of larger dimensions as required to appropriately
support the structure and the sheltering earth.
Since such a foundation (14) will be sub-
jected to environmental forces generally considered
detrimental to wood, the materials should be treated
to resist such effects. Lumber appropriately treated
with chromated copper arsenate works particularly well
in this regard. Lumber so treated is clean, ordorless
and safe to handle. It will also resist fungi, mold,
rot, and various insects such as termites and carpen-
ter ants, and the protective chemical will not leech
out of the wood. Also, plastic sheeting (16) may be
secured around the foundation as shown to provide a
water barrier and to further protect the wood.
Referring now to Fig. 2, the walls (17) may
be generally built in accordance with usual industry
guidelines and practices, with a few exceptions. The
walls (17) are formed about a typical skeleton of
upright studs (18) and have structural plywood secured
2~ to their exterior surface (19). Either plywood sheeting
or sheet rock or some other suitable covering may be
secured to the studs (18) to provide an interior sur-
face (21). Horizontal blocking (22) may also be located
approximately half-way up the wall (17), as depicted.
The blocking members (22) may be slightly offset with
respect to one another to facilitate fastening the
member (22) to the studs (18). The exterior plywood
(19) should be configured such that the horizontal
joint between sheets will substantially buttress the
blocking members, to ensure additional strength.
As depicted in Fig. 3, each ceiling-to-wall
juncture (23) includes a wall stud (18), a ceiling
joist member (24), two top plate members (26 and 27),
a rim joist member (28), a purlin clip (29) and a
sheet of structural plywood (19). These members will
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now be described in detail with reference to Fig. 4.
A first top plate member (26) should be
secured atop the wall ~17) and adjacent to the exterior
edge of the wall studs (18). A purlin clip (29) may
be positioned between each stud (18) and top plate (26)
juncture to increase the strength of each such juncture.
The purlin clip may then be secured in place by nails
or by other fastening agents well known in the art. A
second top plate member (27) may then be positioned
atop the first top plate (26) and appropriately fasten-
ed thereto.
A ceiling joist member (24) having a notch
(32) formed on its end may then be disposed at least
partially about the two top plate members (26 and 27).
Preferably, the notch (32) should have a vertical
dimension equal to the vertical height of the two top
plate members (26 and 27) and a horizontal dimension
somewhat less than the horizontal width of the upper
top plate member (27), such that a rim joist member
(28) may be positioned snugly in the space between
the ceiling joist member (24) and the exterior plywood
sheeting (19).
These various members comprising the ceiling-
to-wall juncture (23) may then be fastened into posi-
tion by the use of nails or the like. Importantly,
each ceiling joist member (24) should be positioned
to rest at least partially upon a wall stud (18) to
accommodate the vertical and horizontal forces exerted
by the sheltering earth.
It should also be noted that the exterior
plywood sheeting (19) overlaps both the two top plate
members (26 and 27) and the rim joist member (28), and
therefore provides additional sheer strength for the
ceiling-to-wall juncture (25).
It may now be appreciated that the ceiling-
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to-wall juncture (23) forms a strong interlocking unit
that strongly resists the weight of the sheltering
earth. This notched arrangement causes the wood to
accept much of the weight imposed upon the structure,
and no one juncture is guarded only by the sheer
strength of a fastening agent. Because of this arrange-
ment, the structure will more effectively resist
nonalignment, slipping and sagging under the weight of
the sheltering material.
Referring to Figs. 2 and 1, it may be appre-
ciated that exterior walls (43) positioned parallel to
the ceiling joist members (24) have a ceiling joist
member (24) attached to their interior side adjacent
their upper edge. For greatest strength, the ceiling
joist member (24) should be secured to the wall (43)
at each stud juncture. This orientation imparts great
rigidity and strength to the structure, and further
assists the structure in withstanding the weight of the
sheltering earth.
With continued reference to Fig. 1, the
applicant suggests that blocking (33) be provided be-
tween both the ceiling joists (24) and floor joists (34)
at locations proximal the walls (17) to assist in
maintaining the structural integrity of the building.
In general, such blocking members (33) should be pro-
vided for the first four feet away from the wall (43)
or less as may be appropriate.
Sheer walls (36) may also be used internal
the structure to assist in strengthening the structure.
In particular, blocking (not shown) may be provided
approximately half-way up each interior wall (36), and
structural plywood may be secured along each interior
wal] (36). Plasterboard or the like may then be placed
over the plywood for a more traditional interior appear-
ance.
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The structure may then be otherwise completed
in accordance with usual construction standards, with
the obvious exception that the roof (37) need not be
finished in the usual manner. Rather, the roof (37)
may be coated with a layer of bentonize mastic or some
similar substance to provide waterproofing and insul-
ation.
A layer of earth (38) may then be placed
atop and around the structure to provide the earth
sheltering. At least eight inches of earth should be
used to obtain important insulating properties, and
this amount should be increased to twelve inches to
support vegetation. Finally, to enhance drainage,
the earth may be leveled such that it begins eighteen
inches thick near the south wall (39) and tapers back
to twelve inches thick at the rear (41).
To further ensure good drainage, rock and
gravel may be disposed about the walls (43) of the
~structure while backfilling the sheltering earth into
place. In particular, coarse crushed rock (44) may
extend from the bottom of the foundation wall to a
few feet thereabove, and a less coarse gravel (46)
may then be used the rest of the way up the wall (43).
Since twelve inches of earth will generally
provide only an insulating R value of from about 5 to
8, fiberglass insulation (42) should be provided in
the ceiling area and in the walls. Although the earth
(38) covering such a structure does not have a high
insulation value per se, its primary benefit in winter
is its action as an air barrier. In the summertime, the
earth sheltering the structure remains cool, and there-
fore maintains the structure within at a comfortable
, level.
; It should be noted that the air space between
the gravel and the floor may be used as a plenum
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chamber to thereby eliminate the need for costly
ductwork for the structure's air circuiation system.
Such plenum chambers are well-known in the prior art,
but are particularly well suited for use in an earth-
sheltered structure as described. Heat from sunlightentering through the south facing windows may be stored
in the gravel during winter for heating purposes at
night, and during the summer, air may be cooled by
passing it over the gravel.
A structure properly built in accordance with
the invention will adequately support the sheltering
layer of earth (38). Furthermore, the unique ceiling-
to-wall juncture (23), cooperating at least in part
with the other above-mentioned construction techniques,
will maintain the structure without significant slippage
or shifting.
By practicing the invention herein, an earth-
sheltered structure may be built that exceeds necessary
structural requirements, and that is both relatively
inexpensive and quick to construct. Being comprised
substantially of wood, the foundation walls, walls,
and ceiling units can of course be pre-fabricated
off-site and thereby obtain the benefit of all-weather
production quality control and speedy on-site erection
Obviously, many changes could be made to the
invention herein that would be obvious to one skilled
in the art, and such improvements are not to be con-
sidered as outside the scope of the claims appended
hereto.
