07:31AM | 09/25/06
Member Since: 09/24/06
2 lifetime posts
We have a house built in 1979 Center Hall Colonial. The house is built into a hill so the front is at ground level and the back foundation is exposed.

The basement is dry, there is a cement slab floor and a 1" inch trench filled with gravel between it and the cement block wall which goes around the entire perimeter of the room.

We've been experiencing some Blistering of the cement block foundation walls. Bubbles of the cement block, but no actually water. This problem seems to be contained to the foundation of the house underground. ( but I've noticed some areas in the back of the house that is above ground with the same problem.

In addition Mold has begun to grow from the 1" trench up the wall.. not much but enough to be of concern.

1) Is this blistering a flaw in the cement block that was used by the builder? Or is this water seeping through the cement block wall?

2) Do I need to replace these blocks or can I address any and all exterior water issues outside the house and simply patch the damaged ones with cement?

3) After I kill the Mold with bleach, can I fill this 1" trench in with cement if I plan on finishing the basement so it doesn't grow back?

4) What exactly does this 1" Trench do? Is it for expansion/contraction of the foundation? Drainage? I've never seen any water in it but there is obviously moisture there since mold is growing up from it.


02:52PM | 09/25/06
Member Since: 03/05/04
301 lifetime posts

well, was an INSIDE waterdiverting system done to your basement? sounds like it. IF so, THEY--the Inside system NEVER stopped/prevented ANY water-moisture from ENTERING the basement wall to begin with, thats right.

IF there WAS...OR....ARE, cracks/other openings on the OUTSIDE of a hollow block bsmt wall then, ONLY way to stop/prevent water from entering THESE openings is from thew Outside. Inside systems at best ONLY DIVERT water that, STILL Enters, under the floor. Its not waterproofing anything, its water diverting. So, since most basements leak/seep due to Outside cracks & others direct openings on the outside, these Inside systems do not seal these openings and won`t stop/prevent mold/efflorescence/insects/radon gas/bowing walls etc.

And, imo honest-many years on hands EXP opinion, these Inside Co`s who leave gaps/openings in walls and/or, along the cove-cold joint allow the real potential for MORE radon gas etc to enter peoples homes, lol, its the truth!

Yes, you-others need to seal all/any openings in floor AND on the outside of the house to stop all these things....water/mold/efflorescence/insetcs/radon etc.

Sealing the cold joint/cove will NOT solve water that enters through cracks `n other openings outside. BOTH need to be done.

We all know the numbers/problems with drunk drivers, about 17,000 die every year. YET, radon gas kills 21,000 people every year but not many want to fully discuss this killer. Yeah, ad after ad about drunk drivers and what, maybe 1 ad/commercial run every 6 months on radon gas, and NOT how to stop/prevent it either.


06:12AM | 09/26/06
Member Since: 09/24/06
2 lifetime posts
I'm not a contractor... so actually I have no experience in this sort of thing (my reason for posting)

But I have NO IDEA if a water divirting system was installed.. We're the 2nd owner of the home ... so I'm assuming in 1979 when they built the home into the HILL that to divert the water run-off they created this system..

And from your post I guesss you're telling me that a smart thing would be to BOTH FILL the GAP with cemment and Trench the Outter wall? ANYONE ELSE?


07:43AM | 09/26/06
Member Since: 08/08/06
2 lifetime posts
The blisters are from water penetration into to block from the outside. The interior gap is for the water that either seaps through or under the foundation wall. The best fix is to dig the trench and seal the walls from the outside. A lot of work but will fix the problem. Patching the wall is just that, a patch. As long as the block has not been totally corrupted and turning to dust, it is only cosmetic. After you waterproof the exterior you can patch the walls if you like.


05:35AM | 10/13/14
Member Since: 08/19/14
17 lifetime posts
its not uncommon for water vapor to transmit thru a wall & 'lift' coatings,,, i expect your coating is drylock type of material rather than a penetrating crystalline material (xypex/kryton,,, from what your post describes a post-construction attempt @ water management,,, IF the exterior wall was waterproofed rather than code-rqd dampproofed, things may be different but they now aren't.

impo, your best bet is removing the failing coating, run a dehumidifier, then apply either of the above 2 products
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