Spray Foam for Heavy-Timber Rim Joist
Climate zone 4 very old house 4 x 8 heavy timber joist header sitting directly on top of the rubble stone foundation wall and the joist timbers 8 x 3 are tenoned into the 4 x 8 joist header. full depth foundation/ basement is where all the mechanical equipment is located , no duct work in the basement. In relationship to grade, one side of the foundation is completely below grade, two sides are all above grade and on the fourth side of the foundation the joist header is above grade, and the basement floor is poured concrete. The basement is not heated. I have closed most of the spaces between the subfloor floor boards and joist header and I will use sealant and can foam where there remains any openings so cold air and critters don’t get up into the first floor. My question is with this type of construction does it make sense to closed cell spray foam the heavy timber joist header around the perimeter of the basement or will cause more harm than good? I’m mostly concerned about the completely buried side of timber joist header, could I be trapping any moisture in the timber header by spray foaming it?
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