| SILLS
There are four types of wood sill construction: platform construction,
balloon-framed construction, braced-framed construction, and the builtup
sill. The sill is the foundation that supports a building and is the first
part of a building to be set in place. It rests directly on the foundation
posts or on the ground and is joined at the corners and spliced when necessary.
Figure 6-8, page 6-8, shows the most common sills. The type of sill used
depends on the type of construction used in the frame. To prevent air
from entering into the building, spread a thin bed of mortar on top of
the foundation wall. This also provides a solid base for the sill. Another
technique is to use a sill sealer made of fiberglass. Place insulation
material and a termite shield under the sill if desired.
PLATFORM CONSTRUCTION
Box sills are commonly used with platform framing, which is the most
common type of framing. These may be used with or without the sill plate.
The sill or sill plate is anchored to the foundation wall for supporting
and fastening joists with a header at the end of the joists resting on
the foundation wall. In this type of sill, the sill is laid edgewise on
the outside edge of the sill plate.
BALLOON-FRAMED CONSTRUCTION
“T” sills are usually used in balloon framing. There are
two types of T-sills: one for dry, warm climates and one for colder climates.
They are made the same, except that in the latter case the joists are
nailed directly to the studs and sills and headers are used between the
floor joists.
BRACED-FRAMING SILLS
Braced-framing sills (Figure 6-8) are usually used in braced-framing
construction. The floor joists are notched and nailed directly to the
sill and studs.
BUILT-UP SILLS
If posts are used in the foundation, use either sills made of heavy,
single timbers or built-up sills. Built-up sills are made with two or
more light timbers, such as 2 x 4s. A built-up sill is used when heavy,
single timbers are not available and lighter lumber (such as a 2 x 4)
alone would not support the building load. Figure 6-9 shows how to make
a corner joint for a builtup sill.
Whether heavy timber or built-up sills are used, the joints should be
over posts. The size of the sill depends on the load to be carried and
the spacing of the posts. The sill plates are laid directly on the post
or, in expedient framing, directly on graded earth. When earth floors
are used, nail the studs directly to the sill.
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