When there are cracks you will see them. That said, small curing cracks are often common in concrete work.

If your builder is experienced, s/he will not pour or build the basement walls before the foundation has cured sufficiently. If you have any concerns, why don't you talk to your builder about them?

If you have an experienced builder this should be the least of your worries.

Good luck on your project.

Small settlement cracks that can potentially let in water will not be visible behind a finished wall and so can't be repaired. However, if the foundation wall is wrapped with a plastic membrane system such as Delta MS water will be stopped before it enters the wall. Major settlement cracks will still be visible from the exterior.

Thanks!

I thought cracks are not easily avoidable (we have some in our current basement). I am going to talk to our builder and see what he says.

Worthy's comment about exterior waterproofing system on the outside face of the foundation and basement wall is very important. That should be part of the construction detailing/specifications for the basement and part of your discussion with the builder.

If cracks are to be detected in a basement, one must be able to see walls and slab. Once finished, cracks will be hidden from view.

Do you know the type of soils and soils conditions common in the area of your project?

Good luck with your project.

Can someone - Worthy or Virgil - address the waterproofing a bit more? The plastic membrane system is significantly more expensive and labor intensive than asphalt foundation coating which has proven to be an excellent barrier. Why change? I know there are always new construction materials that improve on the old, but does this really improve?

Duplicate

This post was edited by worthy on Tue, Aug 13, 13 at 11:16

I have never thought that the asphalt coating was a good system. But it is rather easy and low cost-- and better than nothing.

Duplicate

This post was edited by worthy on Tue, Aug 13, 13 at 11:14

A quick spritz of cut-down bitumen is all that is required in most Codes.

About 20 years ago, the Province of Ontario required a plastic membrane barrier. But after complaints by the big tract builders, the requirement was removed. However, virtually every small and custom home builder continues to use the membrane, and sometimes other measures as well if there is a special concern. (Where you're in a high-water table area or are dealing with continuous hydrostatic pressure, other methods must be used.)

The membrane is a water barrier; but, more importantly, it creates a drainage plane down the exterior of the concrete. Instead of installing a membrane, you can backfill with sand or other well draining materials.

In my market, the membrane is installed by the same trade that does the bitumen spray. In the neighbourhood of $2,000 for both on a 3,500 sf. two-storey. The spray is two hours max and another couple of hours for one or two installers to roll out the membrane and power nail it to the foundation. Hardly labour intensive.

Installing Delta MS membrane

Ok. Labor intensive was not a good choice of words, but then I've never installed it. Around here (north suburban Chicago area), the soil is largely clay and I've seen the asphalt coating used on many homes over the decades with no issues. That's why I asked. And as far as I know, sand is not commonly used in the back fill, but again, I'm not doing the work, only observing. I ask questions that may make some here smack their heads but am trying to understand the *why* of things - it helps me to understand why choice A over choice B.

Virgil, we haven't purchased the lot, so I don't know the soil type, but it's clay around my current house.

Last time I talked to the builder, they said they usually put the insulation outside the cement foundation and walls, and the outer layer of the insulation would have some cement coating to prevent creatures from coming into the house.

I don't know the term for such insulation material, but I will make sure to ask them how they detail the basement so that it's waterproof.

I also wrote "Delta MS membrane" down on my notebook. :)

The thing about bitumen, mopped on "damp proofing", is that it tends to work as an effective exterior drainage plane, so long as:

o It is not damaged during backfilling. A back hoe that drops its bucket against the concrete wall and bitumen coating during backfill will probably scrape off (or at leaste damage) the coating;
o There are no cracks in the exterior concrete foundation/basement wall surface. If cracks take place, chances are very high that the bitumen will also crack (why wouldn't it?) with the result of a direct path for water infiltration.

Clay and other expansive soil types expand with moisture and contract when dry. This continual annual "heave" is one good source of foundation wall cracking. If the hydrostatic level of the soil is high, the subsurface water pressure will force water into the foundation walls and any cracks which may be present over time.

A plastic membrane, properly installed, will help to mitigate or prevent much of this since it is not impacted by concrete wall cracking (unless there is major structural movement or failure).

You originally expressed concerns about concrete cracking. If you are truly concerned about cracking and movement, bitumen damp-proofing will not provide the necessary protection. Only a plastic membrane applied to a foundation properly designed and constructed for your soils conditions, including proper back fill, may do so.

Good luck with your project.

Virgil, thank you so much for the detailed explanation. I'm learning a little bit every day!

I just emailed the builder about my concern, and hope they have a sensible solution with good track record.