Vapor Barrier in Crawl Space

[Kraig Councell]

I was wondering about proper placement of a vapor barrier in the crawl space of my home it has a poured walls foundation, there is also a manufactured home next to me for sale and the future owner was telling me that his inspector said that there should be one put down since there is none under the gravel and I looked at mine and there is none under mine also same buildrer put both houses in, I was wondering can I put this barrier over the gravel and is there a perticular gage of plastic I should use and should any seems be taped off. Thanks for the help Kraig.

[Brooks Burd]

Kraig, Any plastic should do, it only has to be a barrier for moisture. If you plan on being on it often, opt for thicker plastic. Lowe's or Home Depot both sell rolls of plastic. As for on top or under the stones, since the house is already there, laying it on top of the stones will work. If you are having moisture problems, also check to make sure your gutters don't leak and carry water away from the foundation. Also the dirt around the house should slope away from the foundation. If it's not, hire someone to grade the dirt away from the house. Also, Propane heat adds moisture to the air, so if you use propane you may want to invest in a dehumidifier. Good Luck.

[Kraig Councell]

I will be making this the next weekend project to do, when I bought the house 3 months back there was no gutters and so I had seemless gutters and downs put on they have the downs leading out about 4 feet from the house at the bottom. I do heat with propane I will also look into a dehumidifier I did notice at the first of the year I was under the house that the inside of the walls looked wet so maybe that would help. I did notice a rather strange smell that was coming from the basement and you could smell it sometimes in the house but especially if you had the cover off the crawl access I was wondering that maybe it was from not having the plastic down? I remember the inspector saying that the gradding looked good so I should be ok there I think, Should I put the plastic up on the cement walls also? or just over the stone ground. I know one reason the new owner behind me told me that his inspector said the vapor barrier will help keep the steel beems from rusting out I thought that was rather clever. Thanks for the help. Kraig

[wiseguy]

Smart to do the work. The ground under a crawl space or basement can be the major source of water vapor from air migration through the ground and also evaporation from damp ground into the home. Ground moisture barriers stop water vapor rising through the ground and into the home, and also prevent evaporation from damp ground. Ground-moisture barriers should be installed over dirt floors of crawl spaces and under concrete slabs. Reinforced polyethylene plastic makes a good ground moisture barrier. It is important that you have a proper slope under the vapor barrier so you don't end up with water on top of the vapor barrier. Your state government or local code enforcment agency may be able to provide you with the appropriate slope/grading and the ml rating of the poly so your home complies with the relevant Building Code. A vapor barrier can also help mitigate radon penetration, if this is an issue depending on your location.

If the seams of the barrier are sealed with a durable tape and /or sealant, this ground covering can also be an air barrier. Ground-moisture barriers are not effective in crawl spaces with standing water, unless the crawl space is designed to drain water off the top of the ground moisture barrier into a sump hole, equipped with a sump pump. In addition to the ground vapor barrier, it is recommended that all homeowners open/crack a window when shower or running a dishwasher/clothes washer in the winter months.

[Kraig Councell]

Good information from everybody here!!! I never thought about the Radon migration but it is known that this tri county area has the highest radon levels in Ohio so this will help. I dont see any standing water under the house it does seem rather dry but I want to do this for the house maintenance and for our own health come to find out. Thanks again to all!!