Basement waterproofing with dimpled membrane

[Josh]

I'm looking for advice on using dimpled membrane products (e.g. Superseal, Delta-MS, etc.) for waterproofing a block basement wall (this is new construction). My foundation contractor thinks it sounds like a good idea, but he insists that I should use it in conjunction with asphalt/6-mil poly applied to the wall so that any water which does manage to get in around the dimpled membrane still won't penetrate the wall. Intuitively, I agree with him that "more is better" when it comes to waterproofing, but I also know that any water that does get into the wall (and inevitably it will) needs a way to escape. If I apply a waterproofing barrier directly to the outside of the wall, that leaves only the inside of the wall for moisture to escape, which, in turn, limits what I can do in the future in terms of insulation/vapor barrier installation. Obviously there are ways to accomodate "breathability" of the interior of the foundation wall, but it seems to me that a breathable exterior is one of the great advantages of using a dimpled membrane.

Does anybody here have any direct experience with these products? Are they good enough that I can forego additional waterproofing? For what it's worth, none of the manufacturers' sites recommend anything additional under the dimpled membrane. Then again, they also don't specifically recommend against it.

Thoughts?

Thanks, Josh

[marson]

I have used a dimple membrane in conjuction with a peel and stick type membrane. My understanding of the dimple membrane is that it doesn't actually keep water out, it only provides a drainage plane, in effect reducing or eliminating hydrostatic pressure against the foundation. The same thing can be accomplished by backfilling with sand. In order to provide drying to the outside, wouldn't the top of the dimple membrane have to be vented? Not sure how you would accomplish this without having a gap that would eventually fill with dirt/derbris. The type I used (system platon) came with a tapered stip which effectively sealed the top of the membrane, so drying to the outside would be very limited. I'd side with your foundation contractor and use something to dampproof behind the dimple membrane.

[Michael Bulatovich]

Exactly right. The water's supposed to run down the inside face of the mat to the weepers.

Nobody dries the outside of a foundation.

Absolutely, except that in certain circumstances waterproofing might be in order instead. Any water that gets past the membrane will do whatever water would do if there was no drainage mat: evaporate or leak. You should check your local building code as I would be surprised if the installation of a drainage mat exempts you from having to at least dampproof a foundation wall.

[DanG]

I have never heard of planning on allowing water to be able to evaporate/perc/drain to the outside of an underground concrete structure.

I have no direct experience with a dimpled product, but I have used Enkadrain on top of both damproofing and waterproofing. The dimples provide a drainage plane as does Enkadrain. Some areas and conditions require damproofing and others require waterproofing. Waterproofing is more extreme and more expensive.

You might also consider Xypex in addition to other measures. It is a chemical treatment of the interior surface of the concrete that grows crystals to seal molecutar voids in the presence of water.

[v8z]

Not sure if its available where you're building, but you might want to investigate the product "Rub-R-Wall" - 100% polymer rubber mixed and hot sprayed on site.

We're in the final planning stages for a new house in NE Ohio. and several builder's I've spoken with swear by it. I visited a job site where it had been applied and was very impressed. It carries a liftime warranty and they've been around since '89. I contacted the local application contractor, and his price/sq.ft was comparable to dimple combined with a waterproofing.

[Josh]

I'll look into it.

Thanks, everybody, for your input. I guess I'll make sure to waterproof underneath.

[Katherine Jing]

replying to Josh, Katherine Jing wrote: We only produce the dimpled membrane, but also don't know the application. If you would like to know the material knowledge. You can send me email [e-mail]