Page 48 - Masonry and Concrete

Concrete Construction Techniques
47
CONCRETE CONSTRUCTION TECHNIQUES

string tightly from corner to corner using a line level to keep the ele-
vation the same throughout its length. Braided nylon twine works best
because it’s strong enough to pull tightly without breaking. For forms
that are only one or two boards high, supporting stakes should be
spaced along the outside of the string beginning at the corners, at 3- to
4-foot intervals, depending on the height of the form, and at the inter-
section of abutting form boards. The deeper the concrete, the greater
the pressure it will exert on the formwork, so don’t be afraid to use an
extra stake or two to help ensure that forms won’t bulge or bow out of
shape during the pour. Drive supporting stakes slightly below the
height of the string so they won’t interfere with leveling or finishing
the concrete surface.
Set the forms so the tops of the boards are aligned on the inside of
the string line and at the same height as the string (Figure 3-11). Butt

FIGURE 3-8

Average annual frost depth for continental United States (from Architectural Graphic Standards, 9th ed.).

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