I have a dirt floor basement that is 14 feet deep and would like some advice on vapour sealing the floor and how I should go about it. I have already started the project by covering the floor roughly 3 inches think with ¾ inch gravel. I was thinking I would now place the vapour seal over the gravel and then cover it with the remaining gravel. The problem is I don’t know if I should run the vapour seal right against the wall, stop it short a couple of inches from the wall or continue to run it right up the wall until it is above ground level. Any advice would be much appreciated.

Here is some more information:

The house used to sit on a poured foundation but at some point the yard was backfilled and the house was raised a good 10 feet using masonry blocks. The foundation wall is starting to show some age as cracks have developed and becomes quite damp roughly 4 feet up the wall with patchy damp spots 3 to 4 feet beyond the original poured foundation. I have installed a French drain around the front and side of the house where the moisture seems to be the most problematic. Unfortunately it is only about 3 to 4 feet below the surface. I have never noticed any water (even in the heaviest of down pours) accumulate on the floor.

 

The 6 mil poly should over lap about a foot and tape the seams and on up the walls to the floor. Go over and look at
http://ornl.gov/roofs+walls/handbook...cts/index.html

This will show you how ED

 

Thanks for the reply, I tried that URL but could not get the page to load up, server may be down. So you recommend that I run the vapour seal right up to the ceiling? Is there any kind of minimum space required between the wall and the vapour seal to allow for any moisture to evaporate?

Thanks

 

boy try and get back to that www I sent its good on this. We run the poly up the walls put we put 2 " polystyrene on the walls for insulation. you dont say just where you are so its hard to say for you. I would run it up to the sill plate of the home.This should keep it out of the home. You could run a small dehumidifer down there if you want. ED

 

Tried that www again, still not letting me connect. Are you sure the url was copied right?
Thx

 

Try http://www.ornl.gov/roofs+walls/facts/index.html

 

Just a note...

It is important that information given is current to common practices and meets current Building Code requirements.

The article mentioned was written in 1991 although some information is factual and still used, this should not be used as guidelines to your project.

As Ed said, add a moisture barrier. A polyethylene vapor barrier covering the ground in the crawl space/dirt floor basement can keep moisture in the ground from coming up into the space. Lay protective plastic with a 6 - 1 foot overlap on each edge. Protective plastic also should extend up walls and corners four inches. Seal plastic sheets with contractor's tape or caulk. Use sand or bricks to keep plastic in place.

If a protective plastic layer becomes damp on the underside, the vapor barrier is doing its job which is to prevent ground moisture from seeping into the crawl space.

Since you have a basement, you could add the 2" Rigid Insulation but as per Code you must install at least 1/2" drywall as per Firecodes. This is considered plastic and very toxic in cases of fire.

I think in your case, unless you're planning on doing something soon, I would forego the rigid. The vapor barrier will help for now. In addition, a dehumifier might be good to run to help reduce high humidity issues that cold damage your structure.

Hope this helps!

 

Thanks a lot for the help. This is just ment to be a temp fix untill I am able to pour a new foundation so hopefully this will improve my situation in the mean time.
Thanks again.

 

Ok then just do a good job with the poly film all around. It will save your floors for you ED

 

I also plan to insulate the ceiling of the basement. Is it all right to put a vapour barrier over the insulation now that all the floor and walls are covered?

Thanks for the help
Ed

 

Chute,

You can if you like.

 

Just wanted to thank you guys for the help you gave me with my project. I now Have the floors fully covered with vapour barrier now as well as the walls half coved. It is making a huge difference in the dampness down there. The only problem I found was that I could not get the vapour barrier to stick to the walls with the tape I was using. I resolved this by cutting 4 foot long strips of vapour barrier and stapled them to the ceiling. I then taped the vapour barrier to these strips, which were every 4 to 5 feet apart. Eventually I will try to get the vapour barrier sealed against the wall.

Thanks
Ed

 

If I understand correctly, this is an unheated, earthen floor basement. Vapor retarder on ceiling should be placed next to the heated side of the area, meaning that, for instance, if you used fiberglass, you would turn the vapor retarder side toward the ceiling. Placing vapor retarder on unheated side tends to result in problems secondary to moisture from condensation. The condensation will decrease the effectiveness of your insulation, and can cause fungal growth and decay if vapor retarder is not on heated side. Vapor retarders are suppose to retard the passing of warm, moist air from passing into unheated areas such as in walls and beneath floors and into attics.

A vapor retarder over soil and sealed to walls in crawl spaces and earthen basements beneath homes will retard moisture from soil rising into areas beneath home. Overlap sheets of 6-8# polyethylene about 6 or so inches and tape seams with duct tape. Extend up the walls about 6 inches and seal with mastic. Take care not to puncture the vapor retarder. Moisture beneath home can led to mold problems. Crawl spaces and earthen basements should be ventilated. If a vapor retarder is present, 1 square foot of free vent area is required for every 1,500 square feet of ground area.

Soil around home should be sloped to carry away excess water. Gutters & downspouts should be clear and carry excess moisture away from foundation.

Termite research reveals that with the increase in use of rigid board insulation (RBI), there has been an equivalent increase in termite infestations. Pest control operators can't effectively inspect and treat structures for termites when RBI is placed as a continuous sheet below grade. Termite problems in RBI have been identified as a serious problem.

http://www.pctonline.com/articles/ar...Keyword=stucco

Foam insulation below grade has been identified as a "ticking time bomb." http://www.hamment.com/FoamInsulation.htm

While termites do not eat foam insulation, they will penetrate and/or use it as a super highway to reach the wood in your structure. According to the Ohio State University Dept. of Agriculture Extension Service, foam insulation should never be used below grade. http://ohioline.osu.edu/hse-fact/1000.html