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sealing concrete block

Posted by meeotch (My Page) on
Mon, Apr 7, 14 at 18:43

Two questions regarding sealing concrete block: I've got a building built with split-face concrete block (pink, rough textured stuff). It's apparently not sealed, because whenever it rains, the wall soaks up water and becomes discolored. I've had problems with it transmitting water to the interior - there's basically nothing there except for the block, fiberglass insulation, then drywall.

Is there a product that's better than others for sealing the exterior of the wall? Preferably something easily obtainable that doesn't require extensive prep - acid cleaning or whatever. I've found these:

OKON S-20:
RainGuard MicroSeal:
NewLook DriveHard:
NewLoock Proteshield:
Good Ole' Thompson Waterseal:

I believe the first three are silane/siloxane based and Proteshield is "elastomeric" something or other. All claim to be "breathable". They're all available at Home Depot, but as far as choosing one, I'd basically be picking at random. Has anyone had experience with these products?

Q2) This same block has been used to build a retaining wall around my back yard. I don't have access to the far side of the wall, and in one case, the adjoining yard is at the level of the top of the wall - so when it rains, there's wet earth up against the far side of the wall.

Should I bother sealing the wall, or would I be doing more harm than good, as water will get in from the far side, and then be trapped inside the block?

Follow-Up Postings:

RE: sealing concrete block

Were I you, I'd be more interested in the frequency of reapplication.
Find a local vendor of masonry products, and compare

About the wall;
Depending upon the height, it may be retaining and if permitted will have had the drainage addressed.
I'd leave it alome.

RE: sealing concrete block

Thanks for the reply. Re the retaining wall: there are no weep holes or other drainage that I can see. It's been suggested to me that I should drill some, though. Anyway, the wall definitely transmits water and gets discolored when it rains.

RE: sealing concrete block

When masonry walls are placed, and not retaining, there will "generally" be no grout in the vertical joint between the first or bottom course. The generic term for this is open head joints. An equal balance between "neighbors."

Since split-face are a decorative block, the assumption could be made that the wall is yours, and because of the height, more than 2'6", is retaining.

So, the hydrology, which is the redirecting of the accumulation of moisture behind a retaining wall, by percolation, should be addressed somewhere on your property. The exception being that if there are continuos walls on adjacent properties.

The staining is indicative of a membrane failure and unless you are prepared to excavate the upslope property, sealing the face will only accelerate the block deterioration.

RE: sealing concrete block

You've got major issues with that wall. If you have any rain event, the water pressure behind it could cause a collapse. It needs to be addressed immediately if you don't want a disaster on you hands.

The takeaway for you on this is that sealing block does more harm than good. It doesn't fix the actual problem, which is a construction issue where an improper drainage plane on a home exists. On a retaining wall, it's again improper (and DANGEROUS) drainage as the culprit again. You've got some work ahead of you to figure out WHY your home's drainage is compromised. Then, you fix THAT issue, which will make the water infiltration issue go away. Surface applied ''waterproofers'' are useless. They don't address the real problem, and they are on the wrong side of the wall.

RE: sealing concrete block

"Should I bother sealing the wall, or would I be doing more harm than good, as water will get in from the far side, and then be trapped inside the block?"


If you live where it freezes, sealing this could cause catastrophic failure. When the trapped water freezes, it expands and blows out chunks of the block when it does.

This is not a Home Depot do-it-yourself project. Call an expert and get out your checkbook.

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