Floor cracking from fiber reinforcing walls?

[jay156]

Has anyone ever heard of this before? I have a client who says that a contractor repaired her bowing basement walls with carbon fiber strips, and a few weeks later noticed cracking in the floor, and bulging in the center of the basement floor.

The footprint of the house is a rectangle, and the cracking seems worst in roughly in the middle of one of the long walls, running perpendicular to it, across the narrow dimension of the basement, but stopping before the other wall. The crack did appear to be new, with sharp edges. She pointed out other cracks that she said were new that I couldn't easily determine the age of. Some seemed to have a raised lip on either side of them, making me think that they're not new, but maybe repaired and recracked.

My first thought was that maybe the carbon fiber shrank as it cured and pulled up on the footer to which it was attached. But then I would expect to see cracks running parallel to the walls, not perpendicularly, and it doesn't really explain the bulge.

My next thought is that when the contractor was driving in the wedges to tie the carbon fiber into the footer, he somehow broke the drain tile which she has running under the floor around the perimeter, and water pressure caused it to bulge in the middle, and thereby caused the cracking.

My third thought is that she just has a cracked basement floor and is looking to sucker some poor contractor into paying to have it repaired.

Picture is the largest, newest looking crack.

Can anyone help me with any insight? Thanks.

 

[concretemasonry]

I do not think the wall is sitting on the slab.

The wall is a block wall sitting on a footing (probably strip footing) and slab is poured with a 4" thickness bearing on the footing and abutting the wall that is built before the slab. This allows the slab to be poured later and the footing provides a uniform base to set forms on or lay block on.- Take a look at the lowest course of the block wall and you will only see the top half of the " high block.

It is very common detail for both block and concrete walls in residences. Normally the strip footing is at least 8" wider than the wall. An interior drain tile would the about a foot out from the interior wall face or slightly more and it is usually at or below the bottom of the footing.

Dick

Engineer and international traveler interested in construction techniques, problems and proper design.

 

[Ron]

Likely has nothing to do with carbon fiber overlay. Crack appears to have been repaired.

Check location of groundwater. Hydrostatic pressure could do this.
No. 3 is a distinct probability! When repairs are made, things that have been there for years suddenly get noticed.

 

[jay156]

Here is a close up of one of the other cracks that seem to have a "lip" on either side. Not sure what caused it, or if it might not be an old repair, but it's not along the entire length.

 

[jay156]

concretemasonry, I understand the wall is on the footer, but apparently these carbon fiber guys drive in some kind of metal wedge between the block and the floor and down into the footer to fasten it at the bottom. That's why I was thinking that the interior drain tile might have been cracked. Due to vibrations? She wasn't sure what the tile was made of, but I presumed it might be VCT since it was done a long time ago.

 

[hokie66]

None of those cracks are new. I think your third thought is correct.

 

[bookowski]

I agree that cracks don't look new.

Why was her wall cracking/failing in the first place? Is this from a recent flood? Seems like whatever caused wall cracks may have caused slab cracks.

 

[Ron]

Jay...VCT is not used for drainage tile. Most likely vitrified clay or concrete.

I doubt that any procedure used for the carbon fiber overlay would impact the tile. As others, still leaning to No. 3

 

[XR250]

not a chance it has anything to do with the carbon fiber strips. It is not easy to crack a slab.

 

[jay156]

Right, Doesn't VCT stand for vitrified clay tile, or have I been using it wrong all this time?