V-shaped Cracks in Concrete Foundation Wall
V-shaped Cracks in Concrete Foundation Wall
(OP)
I came across some unusual cracks today while inspecting the unreinforced concrete foundation of a semi-detached two-story home in Eastern Ontario. The side exterior wall (on the detached side) has 4 diagonal cracks in two roughly symmetrical V-shaped patterns which begin at each end of the wall (see photos below). There is also a vertical crack running down from the other side of the window. The wall supports two steel beams which appear to support both the first and second floor joists. Roof trusses run parallel to the wall supported on the front and back walls. The cracks have been "repaired" but most of them have reopened. All other basement walls appear to be free of cracks (although they are not all exposed).
I thought it might have been cold-joints from poor construction, but it seems unusually that there would be two of them that are roughly symmetrical.
Could some strange settlement be the cause?
Shrinkage?
Vibration? (there is a regularly used rail line about 40 m away)
Could it be earthquake damage?
Any idea what could cause this?

I thought it might have been cold-joints from poor construction, but it seems unusually that there would be two of them that are roughly symmetrical.
Could some strange settlement be the cause?
Shrinkage?
Vibration? (there is a regularly used rail line about 40 m away)
Could it be earthquake damage?
Any idea what could cause this?







RE: V-shaped Cracks in Concrete Foundation Wall
It could be the steel beam is providing horizontal restraint, as is the slab at the bottom of the wall. Therefore the backfill pressure it causing these kinds of crack patterns.
RE: V-shaped Cracks in Concrete Foundation Wall
Uniform implies what jayrod mentioned regarding the steel beam restraint
Wider at the top than bottom would imply a hard point beneath the V in the foundation restricting vertical settlement, as in a large boulder or pile.
If the cracks were apparent inside, but not outside, then excess backfill consolidation is suspect.
Combinations of the above are possible too...
The cracks tell all... usually.
Mike McCann, PE, SE (WA)
RE: V-shaped Cracks in Concrete Foundation Wall
Dik
RE: V-shaped Cracks in Concrete Foundation Wall
The steel beams are probably providing lateral restraint, but strangely one of the beams is approximately centered over the V-shaped crack, while the the other beam is directly over where the other crack starts.
The cracks in the grout do appear to be slightly wider higher up on the wall. The worst being about 2 mm near the the top and 0.5-1 mm near the bottom. It is also interesting that the cracks appear to stop just above the floor slab (although it is hard to tell with the repair).
The idea of a hard point restricting vertical settlement might make sense, except for the symmetry of the two V-shaped cracks. The bottom of the V of each is about 20 feet apart, and each V starts at the end of the wall on each side. I guess there could be two boulders with their midpoint coincidentally centered on the foundation wall.
I could not see any cracks outside due to 2'-3' of snow. The owner said there are some fine cracks in the parging that may or may not line up with those inside.
RE: V-shaped Cracks in Concrete Foundation Wall
RE: V-shaped Cracks in Concrete Foundation Wall