Foundation Cracks

[Bob W.]

My wife and I have been in our new home (new construction) for 16 months. It's a 2200sq. ft colonial. Approximately after 2 months after moving-in the foundation started cracking. As of today there are

19 or 20 cracks in the concrete walls and floor. Eight of the 20 cracks are in the concrete basement walls. I'm not concerned about the floor cracks as they are hairline and have not changed since I first noticed them. And most of the cracks in the walls are hairline as well and don't concern me because they have not changed either. With the exception of one wall crack all the wall cracks have occurred at beam pockets and basement windows and from what I understand this is to be expected. All the wall cracks are essentially vertical cracks.

There are two vertical cracks however that have me concerned and concerned for sometime now. Crack #1 is the most concerning and starts at a beam pocket and goes all the way to the floor. There is also a hairline crack in the floor where this vertical crack meets and extends about 7 or 8 feet from the bottom of the wall. The vertical crack vertical crack of concern is a tapering crack. It's wider at the top by approx an 1/8 of an inch and pretty much disappears before meeting the floor. This particular crack started as a hairline but has steadily progressed to widen at the top of the foundationwall over the last year.

Crack #2 is vertical crack which starts at a window and goes to the floor. This appears uniform from top to bottom. It has shown signs of movement but very little movement. In fact, the movement is more like an oscillation. It widens and closes and repeats the cycle. This crack is hairline for the most part but I think it might have a relationship with the bigger crack since they are on adjacent corners and only 6 or 7 feet apart.

Being concerned about crack #1 and #2 last year I did a couple of things to monitor all the cracks in the basement and the suspected movement of the cracks in question. I used foil tape and made butterflies to tape across all the cracks. This proved useful on all the cracks as this showed me others were not moving but showed I had two that were moving. On crack #1 I fabricated a movement gauge simply by gluing to nails to the concrete 2 inches apart on both sides of the crack. Using a thin metal rod (about 3 feet long) I curled on end of the rod and slip the curled end of the rod over one nail and rested the rod on the other nail. This cantilevered rod amplifies the microscopic movements of the wall.

Crack #1 moves the most. It actually oscillates a few times then expands. Where as crack #2 only seems to oscillates. What crack #1 seems to do is oscillate up and down then expands a several hundreths of an inch then stops then the cycle repeats itself. It has been doing this now for over a year to the point the top of the crack is about 1/8 of an inch.

I had sidewalks put in recently and I had the contractor who did them look at my foundation and this particular crack. He has 30 years experience with foundation work and comes with excellent references. The first question he asked me was if the sill plates were tightened down. I said no because I discovered there were no nuts or washers on the bolts when I was sealing air leaks from all the penetrations coming into the house. I had found a bunch of nuts and washers in the corner of the basement and figured they were extra and chucked them in the trash. He said secure all the sill plates as tight as you can make them. He also offered the idea that the back fill on this wall was pushing the concrete in. He had noticed the crack seemed to be wider on the inside than on the outside. I'm not easily convince that this alone is causing my problem especially with the crack in the floor that meets crack #1.

I had a structural engineer look at it last year and told me really not to worry about it and just monitor it. If it goes beyone a 1/4" then be concerned. I'm concerned at an 1/8 of an inch and it's still oscillating and moving as I write this.

With those ideas I'm wondering if two things maybe happening. So my questions are; What is actually happening here? Is the ground pushing up or is the corner sinking? How long can I expect this to continue this trend? Will it stop? I don't know what side of the foundation is moving but it seems to me that it just that corner of the basement that seems to move. I haven't seen cracks in the sheetrock. I can't tell if the corner is trying to move away. I also noticed when stomping on the floor in the area of crack #1 it sounds hollow underneath the concrete.

Any ideas or advice? You may direct question here or to my email address. Thanks.

Bob

[Paul Furman]

Do you have expansive soil (shrink-swell)? Either irrigate regularly or pave around the foundation to minimize that kind of problem.

[Larry Davick]

If the structural engineer came with good references, and you trust him/her, then I would be satisfied with the engineer's report. By the way, did the engineer make mention of bolting down the sill plates?

Maybe it's time for another opinion. Have you spoken to the builder about this as well?

Frankly I would be concerned about moving cracks, other cracks are probably shrinkage cracks, and these are to be expected with concrete. I believe that the moving ones should be sealed with caulk, at a minimum. Do you live in a part of the country where the ground freezes? This would exacerbate the problem.

Good luck.

[Art Begun]

Do you have a french drain around the perimeter of the house to take water pressure off the basement walls?

Attaching the nuts to the bolts certainly should be done. When houses are built, if the basement is backfilled before the first floor is framed out, the basement walls can easily be cracked. The framing of the first floor holds the walls in place. Nuts on the bolts certainly would have done that better.

Do your gutters work and is the water kept away from the house?

If the engineer is good but you are still not satisified, then the best thing to do is to have a french drain put in if one is not there and have poor quality backfill replaced with gravel which will put a lot less pressure on the walls. There have been many posts here about how to do this (using landscape fabric to protect the pipe and gravel from filling with dirt, etc). Visit the groups page at

to look up old posts on the subject.

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