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homehelp 08-11-2009 01:25 PM

crawl space
Hoping someone can help me out. I purchased an older home, built approx 1920's and a 20'x20' addition was added to it approximately 30 years ago. This addition has a crawl space that i can acces thru the main house foundation. The crawl space is approx 3' high with a dirt floor. I am looking to eliminate moisture and insulate the heating pipes underneath....vapor barrier??....any suggestions?

There is already some kind of barrier, though i can see mold in some spots


travelover 08-11-2009 02:09 PM

You need to cover all the dirt floor with heavy plastic (sold in rolls at the big box stores). Seal it to the walls with roof mastic.

If the vents can be closed off in the winter, just insulate the walls instead of trying to insulate the whole floor. Use 6" thick fiberglass with the vapor barrier away from the wall. If it is vented and you can't seal it in the winter, insulate the floor with 6" fiberglass using wire inserts between the studs to support the insulation. Vapor barrier goes up, facing the floor..

If it smells musty in the summer you may need to vent it during the warmer months.

frozenstar 02-16-2011 02:26 PM

Travelover has some good points. In addition, you can use a dehumidifier to prevent moisture in your crawl space area. Tested it a lot of times and it really helps. I guess you should try it out as well.

joecaption 02-18-2011 07:48 AM

Did vents get installed when they built it? By code there needed to be vents at least every 10'.
The best ones are automatic opening, Then there's no need to have to open of close them. There about $20.00 each and sold at any box store.
The trouble with adding a dehumidifire is who's going to go under there to empty it? It would need to have a hose added and let it dump into a sump to be pumped out, or a condinsate pump added. Everyone I see is put under the house and no ones ever gone under the house to check on it. By the time they do the control circuts is so corroded it's not working.
For a dry crawl space the grade under the addition must be higher then the outside grade, if not fill needs to be added. A simple layer of 6 mil. black plastic over the soil held in place with 16" insulation ties bent in half will hold it in place. There must be ventalation. most codes want the vents to be 12" above outside grade.
There has to be working gutters or the waters just going to work it's way under the house. Thee can not be mulch piled up againt the house or it will hold in moisture, Grade must run away from the house.
Your going to have to trust me on this one, at least 80% of the work we do is on 100 plus year old houses and we have been under 100's of homes and have seen what works and what did not work.
I've seen companys come in and cover all the vents with foam, tape all the seams in the vaper barrier, run it up the walls and nail it in place with strapping, add a dehumidifier. But they never condisioned the air, never raised the grade, never at least fill in the low spots, never added gutters. There was so much water left laying on top of the plastic due to bad grading and mulch againt the home that all the floor joist were covered with black fungus and looked like they had been painted with black spray paint.
What a lot of insurance companys used to do with old ballon constructed homes is make them completly seal up the foundations because of the fire hazard with that type constrution. I had been under the homes before and then years later after it was closed up. Every one of them now had fungus growing because of the lack of ventalation.

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