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Heide-Marie
Floor Joists

Hello, Our home is at the top of the Chesapeake Bay about 15 feet from a small creek that feeds into the North East River. The house was built in the mid 40's. It has a concrete block crawlspace with a dirt floor and a bulkhead opening. The water table is only about 3-4 feet below the soil and the crawlspace stays damp. Our floor joists are damp and many rotted out with some termite damage. Not sure how to insulate the area and keep the timbers from rotting.

jkirk
Re: Floor Joists

putting a vapor barrier down over the soil in teh crawl space will help but insulating the joist cavity's then installing housewrap to the underside will keep the moisture off the joists and let them still breath outward

ordjen
Re: Floor Joists

One of the more recent discussions in Fine Homebuilding Magazine is that of whether the crawl space should be brought into the building envelope. Here, a super heavy vapor barrier is put on the earth and the exterior walls are insulated. The air vents to the exterior are totally sealed. The floor between the joists are not insulated. The space is then heated as if it is normal living space. This results in humidity no higher in the crawl space than in the house in general. Also, since the space is heated, the floor in foot warm.

I am not convinced that this is a good idea, but it is an interesting concept. Similar discussions are had about whether attics should be brought inside the building envelope.

I inquired at the Spring Home Show here in Portland, Oregon about it. It would cost about $5000to convert a 2000sf crawl space.

ed21
Re: Floor Joists
jkirk wrote:

putting a vapor barrier down over the soil in teh crawl space will help but insulating the joist cavity's then installing housewrap to the underside will keep the moisture off the joists and let them still breath outward

This is probably the best solution to fix your problem. Their are a number of firms I see advertising that specialize in this type of work. I'm in northern Balt. Co., so you should be able to find someone. No reason it couldn't be a DYI project, but a house built in the 40's probably doesn't have much crawlspace room, so crawling and fighting spiders will be required.
Also be sure the house is properly graded so water and downspouts flows away from the building.
Additional foundation vents are probably needed. They are fairly easy to retrofit into a block wall. If you are in a flood plain special vents to control water are advisable and would be required on a new house.
Termites require soil poisoning that is best done by a professional. They may even find more damage than you are aware of.

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