Expert: Dan Griffin - 12/28/2009

Question
We are getting ready to put plastic down in the crawl space of our new house (in W.V.), we are already seeing moisture there on the cement blocks. In two corners there is standing water. Plan to put dirt in the corners but it's snow here and bad weather right now. Our questions is should we put plastic over the standing water or leave that opened until we can fill it with dirt? We haven't moved in yet - have heat in the house and painting interior. Not using any plumbing yet, have not installed toilets/sinks. I wasn't sure if covering the standing water would cause more problems like mold etc. Thanks in advance!

Answer
Pat, the bigger question is where did the water come from.  I sounds like you maybe do not have good positive drainage away from the house and/or a gutter or downspout problem.  If the whole excavation drains to  this one low spot, it may be a great place to consider adding a sump pit. I hope your water table is not this high in the ground.

These floor designs were done for decades without a vapor barrier, but I do realize they are commonly done with barriers now.  Here are two good articles on the issue:
http://www.fcs.uga.edu/pubs/current/B924.html
and
http://www.buildingscience.com/index_html

The idea is to force moisture to stay in the ground or return to it rather than evaporate to be absorbed by the building materials.  If you are talking about open standing water, I think I would deliberately excavate an actual hole and pump as much water out as possible.  Placing the VB on water is what your trying to accomplish.  Do you plan to extend the VB up the stem walls also?  open water will make it very difficult to tape the joints.  A good product to consider would be :one of the commercial heavy mill vapor barriers like Permanator:
http://www.wrmeadows.com/wrm00068.htm
It is much easier to work with than visqueen in my opinion.