Originally Posted By: jonofrey This post was automatically imported from our archived forum.
I did the final on a two phase inspection yesterday and observed a crack in the slab in the garage. This is a post tension, monolithic, slab on grade. I did not observe the crack during the pre-drywall inspection. The crack is about 1/16th of an inch at it’s widest point and ran nearly the entire width of the garage, stopping about 10 inches short of the perimeter grade beams on each side of the garage. Appeared as if someone may have tried to “float in the crack”. There was a scrape or gouge running perpendicular to the crack. Looked like teeth marks from a bobcat.
Buyer called the Super to discuss it with him. Super says gouge is from bobcat cleaning out garage. Says he did not tell anyone to try to repair the crack. Also says they won't do anything to try to repair it.
I called the foundation out as in need of repair and referred to a structural engineer familiar with methods for repairing cracks in concrete. Made mention of my observations and suggested stress crack rather than settlement crack. Also estimated the stacks of brick on the back wall as weighing about 1500 pounds.
My guess is that the crack was caused by a stress load and not differential settlement. No cracks in perimeter grade beams (the good news). Client asked me if I would back out of the deal if it were me. Oh no! Can't go there. Told him I would feel better about it if a structural engineer signed off on it.
Originally Posted By: jpope This post was automatically imported from our archived forum.
My guess is that the crack runs parallel with the stacked brick . Couldn’t quite tell in the pictures. If so, this is a result of the excessive weight.
Post tension slabs usually crack for a couple reasons - improper placement of the cable and excessive perimeter down force are both possible causes.
Check again once the brick has been removed. PT slabs usually "bounce back" and the crack may close up to a hairline.
Did you have a chance to see the slab before the cables were stressed? If this was poor cable placement, the crack would have appeared while they were stressing or within a few hours after completion.
-- Jeff Pope
JPI Home Inspection Service
"At JPI, we'll help you look better"
(661) 212-0738
Originally Posted By: Ron Hollingshead This post was automatically imported from our archived forum.
John,
The thread’s dated but I wanted to throw something out there.
Almost all of our slab on grade foundations are PT here in the Tulsa area, but we frequently pour and finish the garage floor AFTER the main slab. We rod them in to the footing and run rebar in them but no PT in the garage. Reason is the slope in the garage mis-aligns the PT cables, or so I've been told. Most of our concrete is done by hispanics up from Texas so I assume they learned it somewhere
Originally Posted By: roconnor This post was automatically imported from our archived forum.
The first two pics don’t look like a bobcat gouge. Hard to guess at whats going on without more info/observation, but it doesn’t look like a “normal” crack in new construction.
ACI standards limit crack widths to 1/64" due to durability requirements for new interior concrete (ACI-318), but a lot of engineers use 1/32" as a more reasonable limit (e.g. ACI-224). That is assuming it's not flexural bending cracks (tension side) or something that must be watertight, in which case the crack limits are even lower. Pretty small cracks, eh.
Is the AHJ going to "sign-off" on this cracked slab meeting "code" since it's new construction? Asking that question might kick the engineer's evaluation back on the contractor ... or he might just agree with the AHJ to then just fix the crack.
-- Robert O'Connor, PE
Eagle Engineering ?
Eagle Eye Inspections ?
NACHI Education Committee
I am absolutely amazed sometimes by how much thought goes into doing things wrong
. Couldn’t quite tell in the pictures. If so, this is a result of the excessive weight.