Gaps in vapor barrier

Today I was in a crawl space and the vapor barrier that was just installed had large gaps down the middle and around the edges. I recommended that the vapor barrier should be continuous without gaps. The home owner called the contractor that installed it, btw is a large pest control chain. and they said they only cover 80-90 % of the crawl space to prevent it from getting too dry. I had never heard of this! All the research I have done says to overlap and seal the vapor barrier to the foundation etc.
Anyone ever hear of this? We live in an area with a high water table, moisture problems in crawls is common.

The Contractor was full of BS.
You called it right Jon.

Well done.

Here is a little excerpt on the subject.

**Control Moisture in Your Crawl Space **

If your home has a crawl space, now is a good time to inspect it for any signs of moisture accumulation.
A surprising number of homes with moisture problems such as wet windows, mildew on the walls and ceiling, or damp attic insulation can trace their moisture source to a damp crawl space.

Every crawl space should have a ground moisture barrier installed over the bare soil.
A lot of moisture travels from the ground into the air, even in crawl spaces that appear to be dry.

Bare ground can also allow soil gases such as radon, petroleum vapors, or fertilizer residues to enter the home.
If you find bare ground in your crawl space, you should install a ground moisture barrier.
The most common type is a continuous sheet of polyethylene plastic. It can be either clear or black, and should be at least 6 mils (one mil = 1/1000 inch) thick so that it doesn’t tear.
An even better option is reinforced polyethylene, a tough white material that is stronger than normal polyethylene.
Either type should be overlapped at the seams, and sealed with builder’s tape or construction adhesive to create an airtight barrier. Cut your ground moisture barrier plenty big so it can be turned up the foundation walls a foot or two.
Seal these edges to the foundation with construction adhesive.

Here builders tape is used to seal the ground moisture barrier at a seam, at a post and at a tear in the plastic.

You’ll need to find an access hatch into your crawl space, either from the outdoors or through the floor inside your home. Wear good protective clothing, and bring a bright light so you can see to all the far corners. Watch out for protruding nails or other sharp objects, bare wires, or parts of the structure that you could hit your head on.
If your home already has a ground moisture barrier, be sure it is in good condition. You may need to repair any holes or tears, seal the seams, and seal the edges to the foundation. Your home will be drier and healthier as a result of these labors.

Hope this helps a little.

Marcel :):smiley:

Marcel has his number…

I had a pest contractor tell someone the exact same thing last week. I know I heard something about that before myself. I think it had something to do with being too dry for the wood floors.

We have a very moderate climate here, so I don’t think it matters as much. I have NEVER seen a vapor barrier with sealed seams here.

Hey Marcel may I share this with some others? I love giving them little hints like this.

Regular Construction adhesive is not recommended because when it cures it does not stick to the poly. Acoustical sealent is the recommended product because it stays sticky for a long time. The rest of the statement is right on the money.