Insulating the Foundation
There are fancy nail guns with plastic washers that would work well for attaching the foam. Rental shops around here have never heard of them....so on to plan B! We talked about using Lepages PL 300 for foam board. I have used it before but it skins over quickly and it doesn't perform well at low temperatures. Instead I opted for DOW EnerBond SF (Photo 2). It attaches to a re-usable spray foam gun and can be cleaned up with acetone. The instructional information states that it gives full adhesion within 10 minutes and gives full bonding strength within 2 hours. For each sheet we sprayed a 5"-6" line of foam (Photo 3.) on the foundation at the high points on the wall (typically at the position of the intersection of the form panels.). The foam was levelled to the top of the foundation and clamped lightly in place using some woodworking clamps. Since the wall is slightly more than 48" high, the foam is sitting just above the footing; enough to wedge a rock at the bottom of the foam to hold it in place (Photo 4). There is a gap between the bottom of the foam and footer which, for simplicity, I will not be filling with foam. Concrete leaking between the form panels left large knobs of concrete on the footer which could not be removed. The construction drawings called for a 4' frost wall with backfilling to within 8" of the top of the foundation. This requirement will still be met by leaving the small gap at the bottom of my 52" wall.
Work moved along quickly using the clamping method. After attaching about 8x4' lengths, clamps could be released from the foam to be used for the new sheets being applied further down the line (Photo 5-1 to Photo 5-4). Once we reached the higher section of frost wall, the foam sheets were braced with scrap pieces of 2x4 until the glue set (Photo 6-1 and Photo 6-2). With the shiplaps from the upper panels pointing towards the bottom of the foundation, the shiplaps on the bottom foam panels can be slipped up behind the upper panel. Simple wedging with scrap foam keep the bottom sheet in place while waiting for glue to set (Photo 6-2).
The connection between the two foundations (Photo 7-1) were treated in a similar fashion. Foam was abutted into the thermal break with foam glue as in Photo 7-2 and 7-3. Foam then continues along the adjacent wall towards the left. After parge is applied, it will look like a continuous foundation from the outside. This solves the thermal break issue and the foam edge being seen from the outside.
After 11 hours the foundation is about 80% complete (Photo 8). Another couple hours tomorrow and the foundation insulation will be complete!! Its now been 24 hours since we applied the foam and glue. Its as solid as a rock!
Photo 3. 5"-6" of foam adhesive sprayed onto the wall at the position of the form interactions.