Page 52 - Masonry and Concrete

Concrete Construction Techniques
51
CONCRETE CONSTRUCTION TECHNIQUES

on center to anchor the boards to the concrete and keep them in place.
A finishing nail with a small head can be driven slightly below the sur-
face of the wood so that it will not show in the finished construction.
Redwood, cypress, and cedar are often used for permanent forms, but
they must be coated with a clear sealer to protect them from the alka-
lis in fresh concrete. Pressure-treated lumber can also be used but does
not have to be sealed because it is protected by chemical preservatives.
Temporarily cover the tops of all permanent forms with masking tape
to protect them from damage or staining during the concrete pour (Fig-
ure 3-15).

3.3.3 Curved Formwork
To form a radius corner on concrete, you’ll have to build curved forms.
For short-radius curves, it is easiest to use hardboard or plywood for
the curved section. Cut strips of plywood to the same height as the 2
forms used for the straight sections, being sure to turn the grain of the
plywood face veneer vertical so it will bend more easily (Figure 3-16).
Space supports at 1-ft. or 2-ft. intervals. For long-radius curves, use 1
lumber. Wet the wood first to make bending easier, and space stakes at
2-ft. to 3-ft. intervals. It is more difficult to bend 2 lumber, but if you
are building forms that will remain in place as decorative elements,

CHECK NARROW FORMS
WITH CARPENTER’S OR
MASON’S LEVEL

CHECK WIDE FORMS WITH
STRING LINE LEVEL OR WATER LEVEL
FIGURE 3-12
Check forms for level.

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