Drawings and Specifications
for a Greenhouse/Addition
by Stuart Culp
Click figures to enlarge
This document contains the drawings and specifications for
the construction of a residential greenhouse attached to the
dwelling at (Location). Figure 1
shows an artist's sketch of the existing dwelling, the polar
orientation and the location of the addition. Figure
2 shows the east elevation and Figure
3 shows the north elevation. The 14' x 20' x 8' greenhouse
shall maintain a semi-tropical environment during the entire
year for the purpose of housing a private horticulture collection.
Integral to the greenhouse is an enclosed passageway which shall
allow comfortable access to the greenhouse from the dwelling
under all weather conditions.
The construction of the greenhouse and passageway shall be
aesthetically similar to the main dwelling. The greenhouse meets
the Town of (your town) side and rear offset requirements of
10 feet and 30 feet, respectively. The actual offsets are approximately
62 feet from the rear and 25 feet from the side.
Construction of the project shall be divided into two phases.
Phase I includes site layout, excavation, grading, foundation,
passageway, and utilities. Phase II includes the greenhouse framing,
glazing and equipment.
a. Site Layout -- The addition shall be square with the main
b. Excavation -- Excavation includes that necessary for the foundation
c. Grading -- Grading includes that necessary for foundation
backfill and the lawn area designated on Figure
4 to prevent water runoff from accumulating against the foundation.
Some grading is also necessary inside the greenhouse. Note that
there is about one foot of slope from greenhouse end to end.
It is desired to level the interior finished soil surface and
the door sills with the lowest point of the outside soil (the
north end). The interior finished soil shall be one foot in depth,
achieved by removing the existing clay/shale hardpan and replacing
it with topsoil.
d. Foundation -- The foundation shall be constructed so that
footings are below the frost line in accordance with Figure
5. Note that the two doorways to the greenhouse are to be
at approximately ground level for ease of entrance, requiring
that the foundation be relieved at those points. Foundation insulation
is to be applied to the passageway as well as to the greenhouse.
Dimensions relating to the passageway and the distance of the
greenhouse from the main dwelling are nominal. Dimensions relating
to the greenhouse proper are measured along the outer surfaces
of the framing and are exact. The greenhouse length dimension
is arrived at in the following manner (see Figure
9 and Appendix A1, A2,
and A3.): Sheet width = 4'. H profile
= 5/8". Assembly tolerance and thermal expansion (each edge)
= 1/8". 48 + 1/8 + 1/8 + 5/8 = 48 7/8". This places
studs on 48 7/8 / 2 = 24 7/16" O.C.
e. Passageway -- The passageway shall be constructed in a manner
similar to the main dwelling. Siding and roof slope shall match
except as stated below. The slope of the shed roof above the
entrance area to the main dwelling should come as close as possible
to the slope of the main roof, however it will probably be limited
by the clearance between the roof joist and the door. Compromises
in this area may have to be made to achieve a satisfactory appearance.
The interior of the passageway shall be left unfinished, and
the floor shall be dirt. A pressure-treated wood landing with
stairs to facilitate exit from the main dwelling shall be provided.
No insulation other than the foundation shall be provided, however
the treatment of the wall under the siding shall be consistent
with typical, well insulated house construction. The entrance
doorway to the passage shall be located as close to the family
room window as practical. This will be the limiting factor as
to the start of the passageway. The door shall be a standard
2' 6" door similar to other interior doors used in the downstairs
area of the house. A portion of the family room baseboard heater
will have to be shortened to make room for the door, and electrical
wiring in the wall may have to be relocated. The clothesline
canister shall be relocated to the north wall of the passageway.
The floodlight shall be relocated, but the relocated position
is yet to be determined. It is desired that there be no wood
exposed to the weather (no painting).
f. Utilities -- Hot and cold water, natural gas and electricity
are to be supplied to the greenhouse electrical box, heater and
sink as shown in Figure 4. Gas and
water connections shall be provided with shutoff valves at both
ends of the lines. Water valves at the house end shall be equipped
with drains. The hot water pipe shall be insulated. Water pipes
shall be underground to provide freeze protection.
a. Greenhouse Framing--All lumber exposed to the greenhouse
interior shall be pressure treated. Nails shall be galvanized
and screws shall be stainless steel. Construction details are
outlined in Figures 6, 7,
10 and 11.
b. Glazing--The greenhouse glazing material shall be clear,
16 mm triple wall polycarbonate. Glazing, attachment extrusions
and related hardware are described in Appendix A1,
A2 and A3. Note
that it appears as though the extrusions must be slipped onto
the panels from the end, because of the difficulty in installing
from the side. This being the case, the walls must be installed
first due to the roof overhang.
and Operating a Greenhouse in USDA Zone Four
Gardening in a Basement Greenhouse