- Q.
A foundation wall in my customer's
two-story home has a 2-inch bow in the middle of its 53-foot
length and two stress cracks located 10 feet from either end,
all probably caused by backfilling while the concrete was still
green. As far as I know, no rebar was used in its construction,
but at least the 8-inch-thick, 8-foot-high wall was built on
sandy soil with good drainage. A driveway is planned that will
butt up to the wall; is there any way to pin this wall to the
driveway, or should the foundation wall be removed and
replaced?
A.Tim Garrison of
ConstructionCalc.com, a professional engineer, author, and
software producer for the building industry, responds:
While the 2003 IRC (Section R404.1.2) allows unreinforced
concrete basement walls in some circumstances, I've seen far
too many cracked and fractured unreinforced walls to think for
a minute that it's okay to leave rebar out. It's possible to
pin the wall to the proposed driveway slab, but it would do
little good. Presumably the top of the wall is already
connected to the first floor's framing and thus restrained from
further bowing.
Reinforced concrete buttresses connected
to the existing foundation wall and slab floor with epoxied
rebar dowels should prevent further movement in this bowed
basement wall.
But you also need to worry about the midsection of the wall.
Soil is constantly pressing against it and tending to cause the
inward bulge; adding driveway wheel loads will make it worse.
Vertical rebar is normally used to resist this, but in its
absence something else is needed.
While it might be best to tear out the wall and start over,
another much less expensive and intrusive option would be to
build four reinforced concrete buttresses in the basement (see
illustration, previous page). Connected to the wall and slab
with epoxied rebar dowels, these buttresses would likely stop
further structural distress. Plus, the homeowner could use them
for shelving or closets.