Page 202 - Masonry and Concrete

Footings, Foundation Walls, Basements, and Slabs
201
FOOTINGS, FOUNDATION WALLS, BASEMENTS, AND SLABS

taller walls can be roughly marked on the ground with a sack of
mason’s lime so the backhoe operator can see where to dig. The exca-
vations should be wide enough to allow plenty of room for erecting the
forms, with the sides sloped generously to prevent cave-ins.
Foundation walls are typically built of concrete or masonry.
Masonry foundation walls can be constructed of brick or concrete
block, but are usually built of block for its economy and because its
utilitarian appearance is not typically exposed to view. Foundation
walls must be strong enough to support the weight of the building
superstructure and resist the lateral loads of the adjacent soil. They
must also be durable enough to withstand years of exposure to mois-
ture in the soil. Foundation walls may be unreinforced or plain as they
are referred to in some codes, or they may be reinforced with steel bars
for greater strength and load resistance. Building codes typically spec-
ify maximum height and backfill limits for unreinforced foundation
walls and minimum reinforcing requirements for walls which exceed
the limits for unreinforced walls.
The Code provides minimum design requirements based on the
type of soil in which the foundation is built. Figure 6-13 lists soil prop-
erties according to the United States Soil Classification System, which
is referenced in the Code. The minimum requirements of the CABO
One and Two Family Dwelling Code for foundation walls include the
following.

■ Walls must extend a minimum of 4 in. above the adjacent fin-
ished grade where masonry veneer is used and a minimum of 6
in. elsewhere.
■ The thickness of foundation walls may not be less than the
thickness of the walls they support except that foundation walls
of at least 8-in. nominal thickness are permitted under brick
veneered frame walls and under 10-in. double-wythe masonry
cavity walls as long as the total height of the wall being sup-
ported (including gables) is not more than 20 ft.
■ Except for walls with less than 4 ft. of unbalanced backfill, back-
filling may not begin until the foundation wall has cured to gain
sufficient strength and has been anchored to the floor or suffi-
ciently braced to prevent overturning or other damage by the
backfill.

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