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Foundation waterproofing-- interior.

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Anyone have any experience in using Merlex super blockade waterproofing material or have an opinion?

The house I inspected today was built in 1955, and sits on a steep slope with the hillside sloping towards the property (hills overlooking Portland downtown).

The seller paid a waterproofing company $6500 to install 2 coats of this material on the uphill side basement walls (poured concrete). There was a sale fail back in April and the sellers conveniently don't have a copy of the report. I can't wait to see what their disclosure statement says.

Here's what the manufacturers website says: Super Blockade may be applied above or below grade. Two coats are recommended for the positive (source of moisture) side, and for the negative side.

To me, that means the manufacturer requires 2 coats be installed on the exterior and interior since it says "and" and not "or". Any other opinions? The manufacturers set of "instructions" are seriously lacking... :


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I'm skeptical of any basement waterproofing fix that doesn't include provisions for drainage. I see no harm in applying the Super Blockade. But the real solution would have been to install drain tile along the bottom of the footing, run it to daylight, and backfill with river rock or clean sharp rock, or, alternatively, installed Miradrain or something similar on the wall. By doing this, you'd give the water somewhere else to go and make "waterproofing" of the wall unnecessary.

To install waterproofing on the outside of the wall and turn the basement into a boat hull is a risky proposition. Any imperfections in the coating or minor cracking in the wall will cause it to leak again. Even if the waterproofing works, water will tend to then build up against the wall and exert greater pressure on it. This could actually cause cracking, particularly if the pressure builds up in the winter and eases off again in the summer.

If the job included drainage, I wouldn't be too concerned about how the Super Blockade was installed because it's redundant anyway.

- Jim Katen, Oregon

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Thanks for the reinforcement Michael.

If the job included drainage, I wouldn't be too concerned about how the Super Blockade was installed because it's redundant anyway.

If used on the exterior, it would have needed to be installed in conjunction with a footing drain system of course, and ideally back filled just about to grade with gravel. The problem in this case is that there is a newer, very large driveway and porch running along the entire uphill side of the house.

As far as the interior goes..... No, no other drainage work was done.

List of work done......

  • Pressure washed the interior walls and coated them
  • Repaired cracks in the slab floor
  • Installed a new vapor barrier in the small crawlspace on one end
  • Installed a basement dehumidifier

That's it.

The problem is that I have no idea why they did the work in the basement since everything was covered up. All I could say in the report was that they needed to find out why all of the work was done, and that if there was a history of drainage issues, then I questioned the work that was done.

This house is the last one on the hill before dropping off an extremely steep hillside. There is a lot of water draining down towards this property. It's steep enough that at the corner of the garage, there's only about a 2' step up onto the roof.

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Oh, they installed it on the *inside.* For some reason, I thought that it had been applied to the exterior of the wall.

My bad..I just read my original post and realized I didn't make that clear.

That sounds like a good place for a geo tech, geological engineer. I would be concerned with the chance of a mudslide. My yard is flooded today, and the forecast is for rain.

When people spend thousands on waterproofing, it's a good bet it was needed - wet. It does not sound like they dug down on the outside to apply the exterior coat, does it? If they did, then new drainage should have been part of the fix.

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Yeah, excavation on the outside, application of an external membrane and then installation of something like Deltadrain would make more sense than paying someone $6500 to paint the foundation wall. If I were going to pay that kind of money for interior paint, I'd want them to use crystaline waterproofing material (CWM) to stop the water deep in the wall instead of allowing it to get near the face.

Why the fuss? Did the basement re-flood? It's been a really really wet fall and early winter so far; are we making mountains out of a mole hill if there's no evidence it's re-flooded?



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