ASHRAE Journal - March 2010 - 73

Figure 1 (left): Make A Single Zone. Connect the short crawlspace to the basement by removing the short demising wall. Eliminating the rubble demising wall also eliminates two significant intersecting thermal bridges. Photo 2 (right): Knocking Out the Demising Wall. Note the small short column that replaces the supporting demising wall that was removed to connect the crawlspace to the house basement. Photo 3 (left): Disbelieving Neighbor. Yes, you actually can lift a house off its foundation a section at a time, with small hydraulic jacks and steel angles lag bolted into the bottom of the timber frame. We used five jacks rented from the local hardware store: three on the outside approximately 10 to 12 ft (3 to 4 m) apart and two on the inside at the lifting mid points to keep the timber rim beam from rotating. A membrane capillary break was installed between the top of the rubble wall and the timber frame. Photo 4 (center): Foam “Bathtub.” Extruded polystyrene foam on top of a gravel layer on top of the existing combination dirt and broken concrete slab floor. The perimeter drain was located in the space between the foam bathtub and the perimeter foundation wall in the granular layer perimeter drainage zone. A new concrete slab was cast inside the foam bathtub. Photo 5 (right): “Pool Liner.” A sheet polyethylene butyl composite membrane lining was installed covering the interior perimeter rubble foundation wall and the upper short crawlspace floor. This membrane lining was sealed to the capillary break that was installed on the top of the rubble foundation under the timber frame and also sealed to the new concrete slab cast inside the foam bathtub. break, then insulate on the inside with spray polyurethane foam. The approach worked so well we have done a gazillion more in the two decades since. And, so have other folks. Figure 1 and Photo 2 illustrate connecting the two crawlspaces (or mini basements) to one another creating a single zone. Crawlspaces need to be either completely “outside” or completely “inside.” Completely inside is easier when a basement also is involved. The rubble demising wall separating the crawlspace from the basement was knocked out and replaced with a column. Eliminating the rubble demising wall also eliminated two significant intersecting thermal bridges. Note that we also removed and filled in the small crawlspace-basement windows with concrete. These basement windows were nothing more than primitive holes that were, in essence, water leaks, thermal leaks and rot factories. The entire house was then lifted 1 in. (25 mm) to insert a sheet plastic butyl membrane capillary break (Photo 3). And then the house was set back down. This is not as hard as it seems. In fact, it is pretty straightforward. Small 10 ton hydraulic jacks were used with steel angle iron brackets that were lag bolted into the perimeter foundation wood member. We used five jacks rented from the local hardware store: three on the outside approximately 10 to 12 ft (3 to 4 m) apart and two on the inside at the lifting midpoints to keep the timber rim beam from rotating.# # Ask me how I know? Oh boy, did I ever get yelled at by the project architect—my wife. Memo to folks who do this: be sure to get an air gun to install and remove the lag bolts used to attach the angle iron lifting brackets. Goes very fast, very slick. Additional memo to folks who do this: if you run across anchor bolts, just cut through them. You can add a bracket connection on the inside later if the gravity thing worries you. March 2010 ASHRAE Journal

ASHRAE Journal - March 2010

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