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Old 06-30-2010, 09:12 PM   #1
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Long crack in foundation

My cinder block foundation has a crack along its entire length on the side were it is completely covered by soil (uphill). The crack, running along joints, appeared last year and now opened up to 1/16". It is two blocks below the sill. The wall is not bellowed and vertical (as measured with level). About 5 years ago, I had a water problem which I remedied using Drylok paint. There is one down spout from the roof 6 ft feet from the wall. The crack must be caused by tension on the foundation, correct? The only explanation I could have is that the center of the foundation is sinking. Or what else can cause it? Are there methods to fill the cavities inside the cinder block wall with concrete or the like? Would a French drain be sufficient to stop the crack from growing?

Thanks for any advice, Hasso
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Old 06-30-2010, 09:18 PM   #2
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Drylock prevents the water from getting into the basement
It does not prevent it from getting into the block wall

Where are you located ?
What kind of soil ?

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Old 06-30-2010, 10:20 PM   #3
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If the bottom of the wall is fixed, and the top of the wall is fixed, the soil pressure will bend the wall inwardly. This would effectively cause tension on the inside face of the wall, and compression on the outside face of the wall. This could be the cause of the crack. The center of the foundation sinking would likely cause a different crack pattern.
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Old 06-30-2010, 10:21 PM   #4
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My first guess is soil pressure from clay type soils. They tend to swell when they get wet and are hard on basement walls. I don't think the footing is sinking.
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Old 07-01-2010, 04:44 AM   #5
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welcome to the world of masonary block foundation walls,,, they're only cheap during the building phase,,, 1 of our specialties is block wall strengthening & stabilization - ck our w-site for the ' wall pins ' stabilization method,,, we use 12,000psi grout but you could use apron store conc mix.

previous posters are correct and drylock still sucks,,, it prevents anyone from seeing the damage til moisture attacks it too & falls off the wall ! previous owner did it in our home,,, even IF it did work, water's still entering the wall to the level of the drylock so what's the sense other'n it looks nice ? ? ?

its my belief that this type of crk's caused by increasing lateral soil pressure against an unstabilized object ( the wall ),,, low amplitude vibration ( traffic ) over time coupled w/draining water & soil acids all exacerbate the effect til the blocks literally rot & collapse.

Last edited by stadry; 07-01-2010 at 04:47 AM.
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Old 07-01-2010, 10:16 AM   #6
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Very typical sign of wall bowing/deflection from what I can see. Heavy, wet soils, as well as frost often times are the culprit. The best long term fix is going to be excavation from the exterior, straightenin got wall, re-enforcement of wall per YOUR local code requirements, installation of drainage system at footing, damproofing of wall, backfill with mostly stone.

As per the internal pilasters in the block cells, it really depends on your local codes. We used to be able to do it to new const. codes here, but are no longer to use internal re-enforcement w/o an engineering report. You need to get the rebar inside of center of the wall for it to be effective, which is a job of it's own on a retrofit like this. You may be able to install steel wall restraints inside with far less effort.
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