Is "moisture damage" to foundation blocks a real thing?

April 13, 2022 8:33 AM

Is there any value to the expensive "Core Fill" procedure that has been suggested to me? Is moisture damage an actual problem I need to be concerned about? Or is this foundation contractor trying to take me for a ride?

We have noticed that a problem with spall (crumbling concrete) is accelerating on several concrete cinderblocks on the external-facing portion of my house's foundation. We have patched the blocks a couple of times but some of the patch has flaked off as well and we are concerned that the blocks themselves may need to be replaced to prevent a structural issue.

I called in a foundation repair guy to ask for an assessment and estimate for the work of replacing the damaged blocks. He tried to convince me the spall was caused by moisture alone (we think it came from salt damage) and pointed out several other spots around the foundation where barely visible hairline cracks appeared in other blocks. He brushed aside the question of whether the spall-damaged blocks needed to be replaced and presented an estimate for having the entire foundation wall of the house (all four sides) filled with concrete to arrest further moisture from migrating through the walls and damaging the blocks. He also said a waterproof facade should be placed over the spall-damaged blocks to prevent further damage.

This house is in the Twin Cities and the basement is typically dank (addressed with a dehumidifier) and maybe gets seepage of a small puddle from intense rainfall once every two years, which we mop up and that's that.
My questions are:
1) Is the existence of barely visible hairline cracks in concrete foundation blocks a genuine problem, and is the answer filling up the whole foundation wall with additional concrete?
2) Can I expect much the same response from other self-described foundation repair outfits?
3) Is spall damage to 3 foundation blocks (one block, behind the patch, has flaked away so much there's a small hole showing its inner void) a structural threat to the house's integrity?

posted by BigLankyBastard to Home & Garden (2 answers total)

I can't answer all of your questions, but I live in a 1950's neighbourhood with horrible heavy clay soil and concrete block foundations. Every year a few houses near me have to have foundation repairs done. Hairline cracks in old block foundations seem to be common, and to my understanding if they don't move, change, or leak are not a big problem. I've happily ignored a couple hairline cracks in our foundation for over 15 years now, with no leaks. I've never seen anyone in my neighbourhood have the blocks filled with concrete. The usual repair people have done seems to be to dig up the foundation to the footings, replace any degraded block, inject any larger cracks to seal them up, and then waterproof the outside of the foundation and backfill with something more permeable than clay.

You are best to talk to a couple different foundation companies, and if anyone in your neighbourhood has had foundation work done recently, ask what they did.
posted by fimbulvetr at 11:23 AM on April 13, 2022

Agree with fimbulvetr - the way to fix this is first dig the foundation and to waterproof the exterior. Then you can deal with the crumbling concrete, which concrete most assuredly does crumble with moisture - and adding more seems to only push the problem down the road, but I'm not 100% sure.
posted by The_Vegetables at 2:58 PM on April 13, 2022