If you use sand under your house as a moisture barrier , how deep. And do you cover it with plastic barrier as well..?
If you use sand under your house as a moisture barrier , how deep. And do you cover it with plastic barrier as well..?
Up here, sand or stone is just to embed the radon piping in and serve as a solid base for the slab. Usually to the tops of the footings (full foundation or frost walls above, not SOG). Exterior foundation drains (donkey dink with a sock) are at the base of the footings. Poly is an excellent idea (that your flats guy will grumble about).
Plastic on top of sand and below the concrete is becoming the new normal. With poor adhesives(low voc compliant, water based) moisture from the floor tends to pop mastics used for final and vct flooring.
I should have stated this will not be covered with concrete. It an existing room being gutted . The rest of the house crawl space is only exposed dirt. While the floor is removed I wanted to make improvements to the dirt before covering it back up.
Sand is not a moisture barrier.Originally Posted by munchie
The cheapest and most effective moisture barrier is a heavy polyethylene sheet. I have installed a lot of it under concrete slabs.
Also in quite a few crawl spaces. In the crawl spaces it can be put right on top of the existing soil provided there is no debris that can damage it.
A heavy mil sheet will withstand puncturing from small stones.
The price of it may determine what mil you want to install.
You will be amazed how dry a building will be with a properly installed moisture barrier installed under it.
Seams do not need to have adhesive in them as long as you overlap the sheets about a foot.
For slabs, it's best to put a couple inches of clean sand over the sheet. Helps absorb some water - aids placing and finishing, and reduces the curling/cracking to some degree. Also protects the membrane from any imbedded iron.
I'm sitting on most of a roll of StegoCrawl, leftover from an addition project a decade ago - 15 mil. Hope I get to use it before the critturs eat it. I don't go out looking for encapsulation jobs, so I'll probably get buried with it (and the $50 roll of seam tape).
If you need to put sand on top of the vapor barrier to absorb water you must be pouring some very low slump concrete.
There is no cracking and curling on a properly finished concrete surface, unless you poured it too wet or misted the surface with water.
Excessive troweling will cause the surface to get thousands of shallow hairline cracks or can it can even create black spots on it.
The "imbedded iron" should never be so low in a slab that it comes in contact with the membrane.
Ok. Thanks. I will just lay heavy poly
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