# crawl space



## Kls (Nov 20, 2011)

should spray foam include beam pocket or header in dirt crawl space


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## Gary in WA (Mar 11, 2009)

Welcome to the forums!

The beam (wood) needs the 1/2" air space at sides for anti-rot. Don't SPF it. Same with the headers, are you having this professionally done? 
The dirt floor should be covered with a 6mill plastic vapor barrier to meet code.

Gary


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## Windows on Wash (Aug 30, 2011)

Is the beam wrapped in metal at the pocket or some other sort of impermeable protection?

Open sell SPF has a very high perm rating so it will allow drying through it.


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## Gary in WA (Mar 11, 2009)

What is your location?

If under the U.S. building Codes, any beam in a foundation wall requires a 1/2" air space on all sides and end for ventilation. Concrete foundations wick can moisture to the beam (called "rising damp" by BSC) even right through p.t. wood: http://www.ussteel.com/corp/constru...ssure Treated Lumber Constructin Bulletin.pdf



With an open-cell foam surrounding wood with a water/moisture source, you would be courting problems:; ESP can absorb up to 4% water compared to a closed-cell (XPS) only 0.3%: http://docs.google.com/viewer?a=v&q...bY44FW&sig=AHIEtbT1X6_1p3ibUPYAt5jlOsa_kZRRgw
So any ESP touching the concrete can transmit and store water to promote rot of the wood nearby.


Is the crawlspace ventilated, since you are foaming?


Gary


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