rab1234

I am building a new house and the foundation cracked 1 week after pour. The crack runs about 30 feet and is 1/16 inch at the largest spot. My builder tells me it is not a problem until it gets to 1/8 inch.

Is he bullshitting me or is this true?

1slOwCD8

im just giving my opinion not a professional at all, but its the FOUNDATION of your house! i wouldnt want any cracks, no matter how small. if water got in the crack after a while youll be really screwed.

Bill O'Rights

Um...bullshit. You have a crac 1/16 inch wide and 30' long...after one week. Guess what? It ain't gonna get any better. What's it gonna be after 5 years? No...you're the one with the checkbook. Have the contractor re-pour. Not repair...re-pour. Repairs are what you do when it cracks 5 years later, not when it's a fresh pour.

__________________
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xwesleyx

Could be stress cracks that aren't a major concern.

If you are majorly worried, either hire a third party inspector to check it out or call your local building inspector's and ask them what the code is on such a thing.

http://forums.taunton.com/tp-breaktime/login

Check out that messageboard and ask there.

james t kirk

Woe, calm down.

As a structural engineer who designs bridges, I think I know a thing or two about concrete.

1. All concrete cracks.

2. What you are describing is a shrinkage crack most likely unless you can post a picture.

Usually shrinkage cracks are hairline in nature and propagate from bottom of wall up. They are caused because when concrete cures (note the word is cure, not hardens) it creates heat, and stress because it shrinks. There is no known way of avoiding this.

That being said you can greatly reduce the number of shrinkage cracks and increase the strength of the concrete by keeping it wet. Use water, filter cloth, and plastic to keep the concrete hydrated / cool as it cures. Curing takes 28 days officially, but actually quite a bit longer. The slower and cooler that concrete cures the better for everyone. Keep it wet!!!

3. You can also get cracks that stem from any irregularity in the concrete. Like say a cut out for a window. Almost always you will get a diagonal crack that propagates from the corner of the window downwards on a 30 to 45 degree angle.

4. If the contractor used reinforcing steel dowels coming out of the footing and into the wall, the wall will most certainly crack at the bottom of the wall and propagate upwards. The reason is again shrinkage. The concrete wants to shrink, and it will, but at the bottom where the rebar dowels come out of the footing, there is no way, no how that they can give. Result, the concrete cracks to relieve the stress.

5. Cracks in concrete have no effect on the load carrying capacity of the concrete BUT will affect its serviceability (performance). Specifically, the crack WILL leak water.

Now that into itself is not a problem if you properly waterproof your foundation.

In all seriousness, I would recommend that you apply two (2) coats of a bitumen based waterproofing sealer as per your local building code (probably available in the local library or Building dept)

NOW, and this is VERY important, on top of that I would recommend that you wrap the foundation in a drainage sheet such as TerraDrain 121

Linkie....

http://www.webtecgeos.com/prefabrica...ge_systems.htm

This essentially creates an airspace between the outside face of the foundation wall and the dirt used to backfill. The water that would normally be pressed against the foundation wall will pass through the terradrain and just fall right down to the weeping tile.

Very simple, reasonable price, guaranteed to work.

Weepers:

Make sure that you have them.

A superior design is a 100 mm diameter weeper made of PVC pipe, not that Home Depot plastic Shit that is just like drier pipe wrapped in filter cloth. That stuff is shit and will crack and break in 10 years. No, you want to buy the good stuff. It's basically bell and spigot drain pipe that has been drilled. You want to lay down a good quality filter cloth, then encase the weeper holes down with 150 mm of 3/4 washed stone all around the weeper and wrap it all in the filter cloth.

http://www.cmhc-schl.gc.ca/en/burema...abhose_077.cfm

Now, all that being said, the concrete your contractor used is hopefully 35 MPa concrete (I think that's about 3,000 psi, but I am not sure) and is ABSOLUTELY air entrained to prevent freeze thaw damage over the years. (but it's probably too late for that assurance)

The other thing is UNDER NO CIRCUMSTANCES ALLOW HIM TO INSULATE WITH STYROFOAM BLUE INSULATION ON THE OUTSIDE OF THE WALL.

Termites love that shit.

Put the insulation on the inside of the house. It doesn't insulate as well, but you won't have a house collapse from termite infestation.

cheers

james t kirk

One more thing,

My previous post applies to shrinkage cracks.

If your foundation is moving, that's a whole different ball game. Then you are in very big trouble and you need to redesign and rebuild everything.

corktop1

If you have access to a water source it might be a good idea to saturate the ground area near the crack to see if you get any infiltration of free-standing water. If so, this would obviously be a good time to take corrective measures to eliminate that problem before you complete the project, landscape, etc. Doesn't sound to me like you have a structural issue - I have some of these cracks in my foundation wall too - virtually impossible to avoid. Good luck.

rab1234

The crack is in the foundation not the wall. The foundation is set on very rocky ground. I am 2 miles from a rock quary. Had to blast for 2 days to get deep enough to dig the basement. Given that I would have expected the foundation to not move at all. I think the smart thing here is to go check building codes and hire a third party to inspect.

Thanks for everyones help

james t kirk

email me a digital photo or two.