Horizontal Basement Wall Crack

[dtontarski]

I observed a horizontal crack the length of a concrete block foundation wall on the joint at grade level. The wall was bowed slightly inward above and below the crack. I would estimate that the wall below the crack is out of plumb approximately 1/4" per foot. (about 1.5" in 6' of block) The crack is currently a hairline crack, but it is apparent that a larger crack has previously been repaired. Someone (the homeowner most likely) has added some steel post in an attempt to bear some of the load of the structure above this foundation wall.

Question: Should I recommend further evaluation by a PE or a foundation contractor? What are the standards on these issues?

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[Jim Katen]

Originally posted by dtontarski

I observed a horizontal crack the length of a concrete block foundation wall on the joint at grade level. The wall was bowed slightly inward above and below the crack. I would estimate that the wall below the crack is out of plumb approximately 1/4" per foot. (about 1.5" in 6' of block) The crack is currently a hairline crack, but it is apparent that a larger crack has previously been repaired. Someone (the homeowner most likely) has added some steel post in an attempt to bear some of the load of the structure above this foundation wall.

Question: Should I recommend further evaluation by a PE or a foundation contractor? What are the standards on these issues?

Yes. That's a serious structural problem. I'd tell them to hire a P.E. to design a fix and oversee the repairs. Alternately, they could hire the P.E. to design the repair and hire you to perform QC.

- Jim Katen, Oregon

[dtontarski]

Thanks Jim.

[hausdok]

Definitely get an engineer involved.

That's probably inadequate drainage and preparation around the outside of that foundation. The ground is freezing and expanding and has cracked that foundation.

You can find the answer here at JLC: http://www.jlconline.com . When you arrive at the home page, put "block foundation failure" in the search box at the upper left-hand side and it will spit out a bunch of articles on this topic. If you aren't a JLCOnline subscriber, most will cost you, but there are a few that are free to non-subscribers.

OT - OT!!!

Mike

[hausdok]

Hi Again,

To see some details about how one firm approaches basement wall repairs and methods, go here: http://www.structuraldynamics.com

OT - OF!!!

M.

[dtontarski]

Mike - thanks for the advice and good links.

[Steven Hockstein]

I would recommend further evaluation by a Licensed Engineer.

On a similar tangent..

There is contractor in my area that is promoting a foundation repair system that consists of carbon fiber straps that are bonded to the inside of the foundation. Has anyone had experience with this type of repair?

[Bain]

We have lots of clay in our soil, which is highly expansive when it gets wet. Therefore I see tons of those horizontal cracks, which are nearly always caused by external soil pressure. Structural engineers around here favor the method of anchoring I-beams to both the basement floor slab and the main-level floor system so the expanding soil has to effectively move the entire house off of its foundation or seek elsewhere.

[Bain]

Ummm, sort of like Mike's link, which I was too dopey to read until after my post. [:-paperba

[Brandon Chew]

Definitely needs an engineer to design a proper fix. Those columns are doing little more than providing a false sense of security and a convenient place to string a clothesline.

The block wall is being pushed inward, probably from soil and/or water pressure from the outside. Those columns, or anything else that I can see in those photos, are doing nothing to push it back. If the columns are not anchored well enough at the top and bottom, or if they cannot resist the bending forces that would be put on them by the wall (and circular columns don't resist bending well), the wall will take the columns out.

If the columns do hold and the wall reaches the point of collapse, then the columns will probably make a nice decorative feature on the first floor after they tear through the subfloor and the first floor comes down to join the basement. It looks like they are fastened at the top to blocking that is nailed between the floor joists.

[Jim Katen]

Originally posted by Steven Hockstein

. . . There is contractor in my area that is promoting a foundation repair system that consists of carbon fiber straps that are bonded to the inside of the foundation. Has anyone had experience with this type of repair?

I've been hearing quite a bit about that system lately but I have yet to actually see it.

Everything I've heard is positive. That either means that it's a great system or that the manufacturer has a great marketing consultant.

- Jim Katen, Oregon

[Erby]

I've seen the carbon fiber repair once, and attended a brief presentation on it.

Seems like it's a good idea and certainly cleaner than the steel I'beam or column reinforcement.

If you want to see it in action,

1. Take five childrens building blocks stacked one on top of the other

2. Push on the middle block while holding the top block firmly in position.

(The crack that opens up on the opposite side of the blocks simulates what's happening to a concrete block wall like that in the picture.

3. Take a strip of scotch tape as long as the building blocks are tall and apply it firmly down one side of the stack of blocks. This is the carbon fiber strip.

4. Push on the middle block while holding the top block firmly in position.

5. Doesn't move at the middle block crack, does it.

That's a carbon fiber strip system in miniature.

Of course, I don't think any of them are worth a damn thing unless you fix the pressure problem on the outside. And it doesn't stop water coming thru the wall.

[Jim Katen]

Originally posted by Erby

. . . If you want to see it in action,

1. Take five childrens building blocks stacked one on top of the other

2. Push on the middle block while holding the top block firmly in position.

(The crack that opens up on the opposite side of the blocks simulates what's happening to a concrete block wall like that in the picture.

3. Take a strip of scotch tape as long as the building blocks are tall and apply it firmly down one side of the stack of blocks. This is the carbon fiber strip.

4. Push on the middle block while holding the top block firmly in position.

5. Doesn't move at the middle block crack, does it.

That's a carbon fiber strip system in miniature. . .

Erby, thanks for the very clear explanation. I have a question. Frequently, when I see horizontal cracks in basement walls, the concrete is in terrible shape. Perhaps it's just the Portland area but we have lots of crappy concrete in our older homes. (Rumor is that a lot of the aggregate came from the old Rose Park quarry and was full of impurities that have acted like a virus in the concrete causing it to break down over the decades.)

Some of these walls slough off their inner surfaces quite readily. I wonder whether or not the carbon fibers could actually be effectively adhered to this stuff. I'd be like trying to get scotch tape to stick to a piece of cake.

Perhaps the concrete can be stabilized with epoxy before the carbon fibers go on?

- Jim Katen, Oregon

[Rob Amaral]

Jim---there was something like that on TV the other night. An epoxy surface-repair to masonry buildings in SF (down by that Italian Chocolate factory place on the bay). The horizontal cracks in the block I see around Boston are usually frost expansion-related.

[kurt]

Saturation is critical w/any epoxy composite assembly; too much or too little resin will mess things up. Adhesion to the substrate is the other thing; if the substrate sloughs off, the epoxy is worthless. IOW, who's doing the work & how well they do it is the bottom line of performance w/composites; like everything else, it's gotta be done right.

I've got gallons of epoxy & a few yards of various carbon fibers & mats and have used them to fix all manner of stuff. It's absolutely amazing what can be done. While I've never seen the concrete material in action, I've been to the seminar & played w/the samples. If you can get the mix right & get it to bond to the concrete w/out sloughing, I think it would work well.

At least, it would work a heck of a lot better than all the other stupid crap I've seen done as a "repair".

[Erby]

If the stuff don't stick to the wall, at least at the top and the bottom, it don't work worth a crap.

How's this for a "minor" collapse about 5 years after the BDRY type system was installed along the bottom of the wall.

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