403-6875 e-mail us
INSPECTION - Overstressed basement wall
Descriptions: 2 of 3
Inspection was carried out on 3/12/01.
This inspection is limited to the
wall being replaced, and the attachment
of the structure to the foundation wall.
The house is new construction, and is
located on a rural lot.
The structure is a one storey residential
house on a poured concrete wall basement,
and is rectangular in plan with full
walkout along one long edge. The opposite
(north) which must retain earth, is
nominally 9' tall and 8" thick. It
runs 62 ft
without any buttressing. The porch
foundation wall could have acted as a
it was not tied in with reinforcing bar.
The east and west walls are 32 ft long.
Our best information is that the walls
have no vertical reinforcing, and some
Sometime after backfill the north and
east walls showed excessive lateral
at the top, and excessive cracking. The
backfill material has been removed and
walls have not moved back to original
The house is anchored to the foundation
wall with tie straps embedded into the
of the foundation wall at 6 ft spacings.
Assuming light soil pressure for sandy
backfill, 405 lb/ft lateral resistance is
needed at the top of the wall. Friction
able to resist 50 or so of the 405 plf.
This would leave 2130 lb. sideways on
each strap. The straps have deformed ex-
cessively, gouging into the 2x6 base
plate. The best installation involves
straps up through centered holes in the
plate, then bending them over the top and
down the sides. The installed straps were
bent under the plate, and up the sides.
configuration may have less strength, and
will exhibit greater deformation under
lateral load. Cracks in the concrete
propagate diagonally from each strap -
that the straps are (or were)
transferring significant lateral force.
In the best possible case, the straps can
transfer about 480 lb. each - as limited
wood plate's crushing resistance. This
would indicate that the straps must be no
than about 1'-4" o.c.
The Michigan Building Code calls for a
minimum 10" thick wall for this
(Ref: Table 1805.5(1)) Thicker or
reinforced walls may be needed depending
properties of backfill material. If an
8" wall is used, it must be an
reinforced wall. The wall was not built
to Code requirements, and would likely
had performance problems even with proper
top attachment. Calculations show the
unreinforced concrete will go into
tension - unacceptable under the ACI
III. Conclusions: 3 of 3
- The wall is not safe and must be
- The porch foundation must be tied to
main wall with appropriate reinforcing
- The anchors must be installed at a much
closer spacing, in order to transfer the
force into the floor diaphragm. Install
anchors per manufacturer directions.
Consideration should be given to the use
of steel rod anchor bolts in the rebuilt
instead of straps.
- Rebuilt foundation wall must be in
conformance with MBC. Given the trouble
far, and the difficulty in knowing actual
basement wall pressures in general, It is
recommended that a reinforced concrete
wall be designed, or at least any
design be reviewed by the Engineer, and
submitted to the Building Inspector,
- 1200 Troon
- Grand Rapids, MI
[ Home ] [ Engineering Services ] [ Gallery of Projects ] [ Request For Quote ] [ Resources ]
2012 Structural Solutions LLC, 1200 Troon Ct. SE
Grand Rapids, MI 49546 Kent County