vapor barrier importance?

[Bill]

hi. i own a 1999 28x80 brigadier home. It is on a pier type foundation with brick skirting all around...vents installed etc... since setup, the home has never had a vapor barrier under neath, just dirt. It is usually pretty dry under there but sometimes it is damp. should i consider installing a barrier? if so, who should i contact to do the job (i would do it but i hate spiders and other bugs that i know are under there at this time of year, plus i want it done "right" ) how much should this job be on my home? if i do not have this done, what kind of troubles can i have in the future or do i already have them without knowing it? thanks!

bill

[Roy Bonney]

A ground vapor barrier, while being a very modest expense, can greatly reduce the amount of moisture in the crawl space, which can result in some expensive repairs, if left unchecked. The ground vapor barrier, is simply six mil black plastic, installed in such a manner to completely cover the ground beneath the home. This will prevent the ground moisture from coming up into the crawl space. The cost of the plastic is about $40.00 for a 16 x 100' roll, and you will need two rolls. It will take only an hour or two to do the job correctly. The correct application is covered in the installation manual that came with your home.

[Martha Rose Rhine]

Don Lee copied me in your reply to him.

I was told that if the home has a vapor barrier right under the joists intead of on the ground, cover only 80% of the ground at most. The vendor of my home said I didn't need any extra vaor barrier on the gournd at all.

So what if the home already has the vapor barier under the joists. How much if any of the ground should be covered?

MRR

[Roy T. Bonney]

These are two different issues. The one under the joists, was put in place at the time of manufacture. The GROUND VAPOR BARRIER, would be installed on the site. If you read the installation manual that came with the home, it will be addressed. The purpose is to keep ground moisture from infiltrating the crawl space, and then to the home. How important is this ground vapor barrier? It is so important, that under the ANSI standard, if installed, the required skirting ventilation drops ten fold.