Page 204 - Masonry and Concrete

Footings, Foundation Walls, Basements, and Slabs
203
FOOTINGS, FOUNDATION WALLS, BASEMENTS, AND SLABS

■ Concrete and masonry foundation walls must be constructed as
set forth in Figure 6-14 or Figure 6-15 for unreinforced and rein-
forced walls, respectively.

Figure 6-16 shows four basic types of concrete and concrete
masonry foundation walls. In areas with significant risk of earthquake,
building codes typically require more stringent design standards for
all types of construction, including foundations. The map in Figure 6-
17 shows the seismic risk areas for the United States, with zero being
the lowest risk and 4 being the highest risk. Foundation walls in Seis-
mic Zones 3 and 4 which support more than 4 ft. of unbalanced back-
fill are required by Code to have a minimum nominal thickness of 8 in.
and minimum reinforcement consisting of #4 vertical bars spaced a
maximum of 48 in. on center, and two #4 horizontal bars located in the
upper 12 in. of the wall (Figure 6-18). In concrete walls, horizontal
reinforcing bars are simply tied to the vertical bars to hold them at the
correct height. In masonry walls, horizontal reinforcing bars are
placed in a course of bond beam units which form a continuous chan-
nel and are then grouted to bond the steel and masonry together (Fig-
ure 6-19).
The sill plate to which the floor framing will be attached must be
1
anchored to the foundation with 2-in.-diameter bolts spaced 6 ft. on
center and not more than 12 in. from corners. The bolts must extend at
least 7 in. into the concrete or masonry and have a 90° bend at the bot-
tom. For concrete walls, the bolts can be placed into the concrete as it
begins to set and develop enough stiffness to hold them in place. For
concrete block walls, the cores in which anchor bolts will be located
must be grouted to hold the bolts in place. To isolate the grout so that
it will not flow beyond the core in which the anchor will be placed,
the webs of that core should be mortared in addition to the face shells,
and a piece of screen wire placed in the bed joint just below the top
course (Figure 6-20). As the grout begins to stiffen, the bolt is inserted
in the same way as for concrete. Make sure the bolt spacing is accurate
so that it does not interfere with stud spacing, and leave the threaded
end exposed sufficiently to penetrate the full thickness of the plate
with allowance for a nut and washer. If the wall will have stucco or
siding applied, the bolt should be located so that the plate is toward
the outside of the foundation wall. If the wall will have a brick or stone
veneer, the bolt should be located so that the plate is toward the inside

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