Converting old outbuilding to heated workshop
I have a wooden garage, built in 1929 in coastal Maine, in remarkably good shape. It’s got a post and pier foundation and had the front ripped off to convert to a 2 car garage in the 90’s. I plan to reconvert it to it’s original intent as a workspace. Like most of these old outbuildings in our neighborhood, the lawn has grown up to the base of the siding (or maybe they were intended that way) and there is a major negative grade inside, kind of like an earthen crawlspace foundation. When I started digging around and found this out, I got very worried about rot. Turns out after digging far enough to really see under that the structure is in amazing condition underneath! The only rot we have is where a concrete slab was poured at the front to accommodate the drive up to the garage door. The slab was poured against structural posts and those rotted. I assume this situation has worked out ok because any moisture that accumulates underneath can breath through the perimeter and up through the uninsulated and unheated space.
My concern is this. I intend to insulate the interior space. This won’t be a rough workshop. I make musical instruments and need fairly consistent conditioning. I also cannot afford to lift the building and pour a new foundation. If I insulate while leaving the underside to breath, could I cause a moisture trap inside the building? Or is it better to excavate the sides for better airflow underneath, then air seal and insulate the floor?
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