Closed cell spray foam over old mudsill
I have a 1920s duplex that has a large old growth mudsill. The inspection report said that a few parts of the mudsill had some moisture damage. The reason for this moisture damage is probably because of the excessive moisture in the crawlspace. Currently, the crawlspace is vented without any vapor barrier. There are no downspouts that bend away from foundation and in fact, some portion of gutters are missing.
I have a contractor who wants to turn the crawlspace into a conditioned crawlspace. He wants to run 10 mil vapor barrier up the brick foundation up until the bottom of the mudsill. He then wants to use closed cell spray foam on the walls and on the mudsill, leaving a one inch inspection gap on the mudsill. However, most of the 8 x 8 mudsill will be covered on the interior with spray foam.
Is this a good method? Or should I go with foam board insulation and leave the mudsill exposed.
Thanks for any good advice.
GBA Detail Library
A collection of one thousand construction details organized by climate and house part