Here's a pertinent previous thread.

Approaches vary depending on the existing and worst-case water table, annual rainfall and native soils.

Thank you very much!

Okay, my husband has more information. Our contractor is giving us the choice of two products - one is half the price of the other. The first product is called Tremco TP-60 Liquid Membrane waterproofing with protection mat and the other is Voltex Bentonite waterproofing with Aquadrain Protection/Drainmat.

Any opinions on the two products?

Thanks

I have not used either of these brands.

Bentonite has a long history of being used to stop water flow. Your contractor is using it in conjunction with a permeable dimple membrane, presumably so the water flows through and activates the Bentonite.

Only because I have successfully used similar methods, I'd be partial to the Tremco, plus mats. It provides two layers of protection.

Neither of these methods will likely protect you against rising water tables which will come up through the floor. In any case, manufacturer recommended application methods should be followed to a tee.

It's good to see the progress builders have made in this area. When I first applied to use crystalline waterproofing on a foundation in 1991, I had to present evidence to the building department that it was a suitable substitute for the then Code minimum asphalt cutback.

Here is a link that might be useful: Waterproof Magazine: Dimple Membranes

The general thought process seems to be to build a reverse swimming pool and seal it so that no water can get from the outside to the inside, either the walls or the floor. Nothing wrong with taking those precautions. But the more effective approach is to make sure that no water collects on the outside at a level higher than about 6" below the level of the floor. An effective drainage system at that level is the best first step to a dry basement. Then add the other measures to that.

Thanks you all for your input. Our walls are concrete block and have been poured solid with concrete (in Florida I don't think we have figured out forms and pouring vertical slabs - :) ) The foundation floor will be 6mil visqueen (sp?) termite treated, with 4" fibermesh poured slab.

Even though our lot remains dry, we decided on the exterior walls to be overly cautious. We installed a drainage system around the footer - perf. pipe, covered with gravel and soil mat. The walls were covered with the Voltex & Aquadrain mat.

It was a little more expensive but our thought process was that the $ spent now would be a lot cheaper than $ later if we had to make a repair.

Also, in discussing the options with the rep the choice made was also driven by the fact that the liquid membrane breaks down over time. This other method is a natural product and therefore does not.

Thanks for all your input!

Our walls are concrete block and have been poured solid with concrete

Jeeze, why didn't they just order solid blocks to begin with.

liquid membrane breaks down over time.

Yes, but even warranties on these products run 20 years and the lifespan is likely much longer. Plus the associated solid membranes have a lifespan of 50++ years. One manufacturer used to estimate a 300-year lifespan. (Like anyone is coming back in say, 250 years, to challenge that claim!)

Your choice sounds fine.

Worthy - great point! I wonder how many companies are around 10 years from now!

"Our walls are concrete block and have been poured solid with concrete"

The block cavities may have had rebar inserted prior to the pouring/grouting. Many codes require some percentage of the block cavities to be so reinforced and filled. New house near me used the rebar and brought in a concrete pumper for the cavity fill.

Magic 530,
Do you happen to have some numbers with regard to the price difference between a raised foundation and the basement that you built? I live in California and I would like to put in a basement under a proposed house and nobody has an idea of what it will cost. I am thinking about importing a contractor from north Dakota.