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Bulging Masonry Block Wall

Bulging Masonry Block Wall

Bulging Masonry Block Wall

(OP)
I recently inspected a fire damaged home for an insurance company. It's about 40'x40' and the fire was limited to a corner of the main floor. The house was built in the 1940's with a masonry block basement wall with about 6' of backfill. Main floor joists and sheeting is reasonably unscathed and fire did not enter the basement at all. The ambient temperature is well below freezing here at this time of year(-30C). My scope is limited to the basement to assess the damage.

There are number of vertical and horizontal cracks in the masonry block wall, and a number of them look quite old. There looks to be a fresh 5 mm horizontal crack running mid height most of the length of the two exposed walls. My thought is the fire fighters would have shot a good volume of water down the basement wall, and it would have froze to either widen the crack or make a new one. Maximum total eccentricity is about 7/8". Blocks are 8"x8"x16" with mortar horizontal and vertical.

I'm looking to know if there's an upper limit on "safe" wall eccentricity (2 to 3 inches, etc.), or if I should simply look at estimating lateral forces and look to ensure there's sufficient dead load from above to balance the lateral load. Judging by new and existing cracks it's safe to say there is no reinforcing steel or grout fill in the cells.

I suspect I'll be suggesting a fibre reinforced repair or a steel beam repair, but another interesting question will be whether the insurance company should be in the hook for repairing or replacing an old foundation that was in a terrible state of repair pre-fire. Any comments or suggestions here would be welcome.

Thank you in advance.

RE: Bulging Masonry Block Wall

Probably not grouted or reinforced according to the timeline of construction. You could tell though with a small hammer and the pitch generated. If the cells are grouted, it will be more of a solid thud as opposed to a higher ping. The water on the outside from the fire could have frozen, too, on the outside, pushing the wall in. It could have generated a hydrostatic pressure before freezing too.

FRP wrap on the inside might work, but I would lean to replacing the wall in it's entirety. Too much of a liability to me to do otherwise. The insurance company signed the policy and got the premiums. I would not worry about them. Worry about your liability and the safety of the homeowner. Those are your first priorities.

Mike McCann, PE, SE (WA)


RE: Bulging Masonry Block Wall

(OP)
Thanks for the advice msquared. It's much appreciated.

Anyone care to comment on eccentricity that is typically considered safe?

RE: Bulging Masonry Block Wall

I don't have the standards on hand - but I would look into construction tolerances.

If they could have originally built it with that bulge - I'd be inclined to accept it.
If not - I'd be included to reject it.

RE: Bulging Masonry Block Wall

I would tend to agree with msquared.

I'd have to relate the lateral movement to a deflection criteria to know what's acceptable. the 7/8" that you have equates to l/120 (approximately assuming an 8' basement wall). That's too much deflection for me. I would also never accept a newly built wall that was 7/8" out of plumb over 1 floor.

RE: Bulging Masonry Block Wall

(OP)
Agreed. Thanks all for your advice.

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