On Site With Form-A-Drain - Continued
We work our way around the foundation, measuring off the string
and setting both the inside and outside forms as we go. Wire
spacer straps provided by the manufacturer help maintain the
correct spacing between the forms, and a few stakes keep
everything in position (Figure 5). We don't bother leveling the
formwork until all the forms are set; then we do it all at once
with a rotary laser. We hold the forms about an inch off the
stone in case we need to tap down a high spot when we're
Figure 5.Once one side of the
form is positioned, spacer straps automatically locate the
opposite side (left). Pieces of strapping secured with drywall
screws (right) are a good solution when you don't have the
right size, or for nonstandard footing widths.
Figure 6.A worker makes a corner from coupling
stock by carefully taking two 45-degree passes with a circular
saw to remove a 90-degree wedge from one side.
Custom corners. The
foundation shown here had several jogs, which used up our
supply of corners. Fortunately, they're easy enough to make
from coupling stock (Figure 6). Also, there was a place where
the footing widened from 16 to 24 inches. The offset was too
short to fit two normal corners, so we made up a customized
shortened one (Figure 7). We saved the three-sided bump-out for
last, because it's easier to form odd angles when the adjoining
sections are already in place (Figure 8). Where this footing transitioned from 16
to 24 inches (left), there wasn't enough room for two corners.
A shortened corner patched with duct tape solved the problem
Figure 8.The crew saved this 45-degree bump-out
for last. The angles are fairly easy to form because the
slip-on fittings provide 2 inches of leeway.
Once we've set all the forms and everything is screwed
together, we install a pair of crossover pipes to connect the
inside and outside forms. Otherwise, water collected by the
inside form would have no way to drain. We also install an
outlet adapter, which connects the Form-A-Drain to a daylight
drain (Figure 9).
Figure 9.Using a hole saw (top left), a worker
drills a 31/2-inch hole in the side of the form for the
crossover pipe (top right), which allows the inner form to
drain into the outer form. The pipe adapter attached to the
outside form (bottom) will connect to the daylight
Leveling the Forms
Once the forms are installed, we bring out the rotary laser and
level them, and then secure them to the stakes. One difference
between Form-A-Drain and conventional form materials is that
you have to use a lot more form stakes. Otherwise, the plastic
material will flex under pressure from the concrete. The
manufacturer offers metal stakes in 18- and 30-inch lengths and
suggests using one every 3 to 5 feet. You also can use wood
stakes or regular form pins, but the CertainTeed stakes are
inexpensive so it's no big deal to leave them in the ground. We
secure the forms to the stakes with screws.
The manufacturer recommends removing the spacer straps for
reuse once the forms are secured to the stakes, but they, too,
cost very little, so we leave them in place for additional
Prepping the Slab
Often we'll leave a mini excavator and a pile of gravel inside
the foundation footprint and spread a layer of gravel before we
pour the footings. The gravel provides a free-draining base for
the basement slab and gives additional support to the inside
form. The next day, after the footings have firmed up, we drive
out the excavator and start setting foundation forms.
If tying up the excavator for two days isn't feasible, we'll
pile some gravel in front of the forms with a shovel to help
hold them in place, then bring in the excavator to spread the
rest of the stone while we're setting the foundation
When it comes time to backfill the foundation, we bury the
Form-A-Drain forms beneath about 12 inches of washed stone with
a layer of filter fabric on top (Figure 10). CertainTeed makes
a version of Form-A-Drain with filter fabric already applied,
but we haven't used it.
10. Like any perimeter drain,
Form-A-Drain must be protected with clean stone and filter
fabric. Note the optional connection for a radon
Form-A-Drain works fine for most jobs, but forming up and down
on exposed ledge can be more challenging with this product than
with wood. Depending on the type and amount of ledge, it also
may be tough to assure an effective drainage system. Small
sections are okay, but for larger areas it's frequently easier
to use conventional forms and footing drains.
Form-A-Drain is offered in only three depths — 4, 6, and
8 inches. If you need a thicker footing, you have two options.
You could dig a shallow trench and set the forms above it. (For
example, for a 12-inch-high footing, you could dig a 4-inch
trench and put the 8-inch Form-A-Drain on top.) The second
option is to leave a 4-inch space between the bottom of the
Form-A-Drain and grade, and fill the void with dirt or
Cost and Learning Curve
With my own crews, it took just one or two installations to
learn how to use this product, and installation takes no longer
than installing conventional forms. For the project shown here,
my three-person crew had the footing formed up and ready for
concrete in about three hours (Figure 11).
Figure 11.The foundation shown in this article
measures 44 by 30 feet, and has 11 corners and a three-sided
bump-out. Form-A-Drain installation took a three-man crew about
three hours and cost around $450 in materials.
Builders sometimes tell me they think footings will cost more
using Form-A-Drain, but when I factor in the labor savings I
think it's cost-competitive. The components for this
44-by-30-foot foundation with 11 corners cost about $450.
Pagurko owns Pagurko Builders and
PBI Dirtworks in Newcastle, Maine.