Repairing a Bulging Foundation, continued
Making a Deadman
Once all the reinforcing steel was in place, I ordered
concrete for the footing (Figure 4). We used a stiff mix;
although I didn't do a slump test, I estimated it at around 2
or 3 inches. A stiff mix is tough to work around rebar, but I
wanted the concrete as strong as possible. Fortunately, we
could get the chute all the way around the pour, so at least we
didn't have to drag the concrete through the rebar. We used a
vibrator to prevent voids, plunging and removing it about every
12 inches. While the footings set up, we went to work on the
other damaged section of the foundation, where we had to form
and pour a new reinforcing wall on the inside.
Figure 4.The heavily reinforced deadmen (top) act
as footings (center) for the new front porch (bottom), which
adds its weight to the resisting force.
A New Wall Inside
The second section of foundation in need of repair was bowing
worse than the section behind the porch. We didn't have
anything as massive as the porch to act as a deadman on this
section of basement. My engineer and I decided that stabilizing
the basement wall on the inside with a new poured reinforced
wall would work well. We would also tie the existing bowed wall
to two concrete deadmen outside.
Just as in the area behind the porch, we drilled through the
wall and inserted 3/4-inch threaded rod about halfway up the
wall, then welded it to rebar placed in two 8-foot-long
trenches (Figure 5). The two concrete-filled trenches would
ultimately be hidden below grade. We poured the trenches, then
tightened up the nuts on the steel channel.
Concrete Deadman With Interior
Four-foot-deep trenches (above) partially
filled with concrete anchor the steel channel "plate washer" in
this section of the foundation. The new reinforced concrete
wall, poured in a one-sided form, consolidates the existing
wall (drawing, top).
For the new wall, we placed 1/2-inch rebar placed on 1-foot
centers horizontally and vertically. We secured the reinforcing
grid by tying it to 1/2-inch rebar pins drilled into the
adjacent walls and floor (Figure 6). After the rebar was tied
off, we could really see how much the wall had bowed —
about 4 inches in the center.
Figure 6.After tightening the nuts on the steel
channel, the author placed a grid of 1/2-inch rebar (top)
behind a carefully braced one-sided form (center). To prevent
the form from moving, the kickers along the floor were secured
with 6-inch lengths of rebar driven into drilled holes in the
existing slab every 18 inches (bottom).
While I've never had a blowout, pouring one-sided forms always
makes me a little nervous. Adequate bracing is essential. My
customer had maintained her good humor throughout the earlier
process, but I thought two yards of slumping concrete sitting
in the basement might be too much for her to take. To keep the
concrete behind the form, we fastened six horizontal kickers to
the floor about 18 inches on-center, using 6-inch pieces of
rebar drilled into the floor.
Pouring Inside the House
When the day of the pour came, I double-checked the forms and
waited for the truck. The day before, we had built a small
chute to help get the concrete inside. Once the truck was on
site, I checked the mix. I wanted a stiff mix to minimize the
strain on our one-sided form. What we got was perfect; we
literally had to drag it down the chute. We originally planned
to make the pour all at once, but when we got about two-thirds
of the way up, I heard a little creak coming from the formwork.
It was probably nothing to worry about, but rather than risk
disaster, I decided to finish the pour the next day. Once the
forms were stripped, we drove the pins securing the formwork
below the floor and patched the holes.
Both repairs turned out well, and my customer was happy with
the results. While we couldn't straighten the foundation
entirely, the inside is straight and true, and I'm pretty sure
it's stronger than the original foundation ever was.
Gene Lorsonis the owner of Lorson Builder near Hope,