# Trying to update 60 year old basement/crawl... many issues & questions



## algored2deth (Jan 7, 2011)

Anything said here needs to be tempered with local bldg codes. 

1) I would consider this condition spaced since you have h/w tank and furnace in the crawl. In that case, close off the vents permanently. 2" XPS rigid would be good. SF it in with the can stuff. Or caulk with silicone if you do a tight fit with the XPS to the opening.

2) If you have moisture issues, solve those first. If you had frost, that meant it was cold and there was moisture present as well. I would air seal all that you can (rim joist for example). 

3) You will probably need a vapor barrier over the whole floor and ran up the walls 6". If you spray foam the walls, vapor barrier first than SF over the portion that runs up the wall. Vapor barrier will need mechanical fastening of some sort before SF.

4) As for covering the SF on the walls, you can use drywall which implies you have to build studded walls. You will have to use moisture resistant drywall, mesh tape, and sandable 90 type of wall compound. This is compound you have to mix yourself, not the standard premixed stuff. Putting regular paper based products in a moist area is a food source for mold. Or you might get away with intumescent paint. If you are having the SF done by a contractor, ask them for their take. Be aware, this paint is not cheap. 

If you close off the vents, the moisture will remain unless you seal all air gaps and control the vapor coming through the ground. Once that is done, and if you still have high moisture, you may be stuck with getting a dehumidifier. You should get an idea of how much moisture you have now so that you can determine what the change is after you do your work. Sometimes you got to babystep it. Also, use a decent vapor barrier and not just some poly from the store. Your old one may have been destroyed due to nonideal soil content (ie it ate through the plastic). Vapor barrier sources: Tu Tuf, Drylok, ibuyplasticnow.com, stego products, etc. 

I would try and level out your whole crawl floor as much as possible. Get the SF to cover as much as possible. You will be scrubbing a lot of walls there because you need a fairly clean surface for the SF to stick to.

And I am sure that others will be along to provide appropriate links to the buildingscience website. Check those out as well.


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