Page 212 - Masonry and Concrete

Footings, Foundation Walls, Basements, and Slabs
211
FOOTINGS, FOUNDATION WALLS, BASEMENTS, AND SLABS

prevent possible collapse of the wall. Walls
should be allowed to cure for at least three GROUTED
CORES
weeks so that sufficient strength is gained
before any backfilling may begin. The
gravel and soil backfill should be placed in
depths of 12 to 24 in. at a time to avoid
large impact loads against the wall.
6.3.3 Formwork

Forms for concrete walls may be built of
lumber or of plywood, so long as they have
sufficient strength to resist the pressure of
the wet concrete. The taller the wall, the
greater the force exerted by the wet con-
crete and the stronger the forms must be.
For short walls, lumber forms are easy to
assemble and are economical, especially if
METAL LATH OR WIRE
the form boards can be reused in framing SCREEN OVER CORES
TO SUPPORT GROUT POUR
the structure or for future formwork. For
3
taller walls, 4-in. or 1-in. plywood braced FIGURE 6-20
with 2 4 frames are more economical.
Grout screen.
Lumber forms should be fitted tightly
together so the concrete can’t leak out, and braced with vertical 2 4
studs at 24 in. on center. Plywood forms should be braced with verti-
cal 2 4 studs at 16 in. on center. For plywood forms, double 2 4
wales should be placed horizontally at 18 in. on center, beginning 12
in. from the bottom of the form (Figure 6-22 right). For lumber forms,
double 2 4 wales should be spaced 24 in. on center, also beginning
12 in. from the bottom of the form (Figure 6-22 left). At the corners,
alternating wales should run long so they can be nailed or srewed
together for added strength (Figure 6-23).
Wall forms must incorporate ties or spreaders to keep the sides
from bowing. One of the simplest methods uses wire snap ties which
simultaneously hold the side walls of the forms together to prevent
bulging and keep them spread apart at the right dimension. Snap ties
should be located on 16-in. or 24-in. centers midway between each
vertical stud and arranged in horizontal rows at the same height as the
5
wales. The forms are drilled with 8-in. diameter holes at the proper

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