Cracks in basement foundation walls and floor

noah_2008September 26, 2010

Hi all. I would appreciate some advice on this issue as I am getting conflicting opinions from local contractors.

I have just moved into an 8 year old house and we are looking at finishing the basement. The floor of the basement has 3 long cracks, each very narrow (1-2 millimetres at the most) with no shifting or lifting of the floor anywhere. Additionally, there are 4 very narrow cracks in the walls of the poured foundation which are visible on the inside and the outside (where they continue above ground level). The cracks in the walls are also very narrow (really just hairline cracks), but they appear to go right through the wall.

Being a fairly new house, the foundation has a properly functioning weeping tile and a dimpled plastic membrane surrounding the foundation. There is no evidence of water ingress anywhere in the basement despite heavy rainfalls and despite all the cracks.

The question is: do we need to repair the cracks prior to finishing the basement (floor and wall)? If so, what is the best approach to fixing them?

I have talked to several contractors who have told me that the cracks do not need to be repaired because the waterproofing membrane and weeping tile will prevent hydrostatic pressure from building up, thereby preventing a leak through the foundation cracks. I am really not sure whether I trust this advice.

Any insight from forum members?

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These are settlement cracks of no significance. The performance guidelines I build under require no repairs to any cracks in concrete floors or poured foundation walls that are less than 6 mm. (See link below, pp.24-28.)

Were the wall cracks wider, the standard repair would be epoxy injection.

Epoxy injection used to repair minor cracks in new home foundation.
Photo: Heather Joy Investments

Here is a link that might be useful: Construction Performance Guidelines

    Bookmark   September 26, 2010 at 2:49PM
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Would you recommend undertaking the epoxy repair just to be on the safe side? (before finishing the basement, since once I finish the walls, I can no longer monitor the status of the cracks)

    Bookmark   September 27, 2010 at 9:30AM
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If that's all that's happened after eight years, I wouldn't bother. You might want to note though where the wall cracks are, just in case. They usually appear at the window corners, as in the photo above.

    Bookmark   September 27, 2010 at 9:35PM
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We just had our cracks and rod holes repaired in preparation for finishing the basement. It cost $1,000. Only one of our cracks ever leaked and only when it rained super hard.

    Bookmark   October 11, 2010 at 12:35PM
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Excellent advice from the pros.
Concrete will crack unless the quality is extraordinary and higher.
IMO, as an amateur, I would assure that 99.9% of the rainwater flows away from the house at least 3 to 4 feet.
Also, if the crack is too narrow, the epoxy cannot flow. Maybe a paint???

    Bookmark   October 13, 2010 at 1:48PM
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