After Mike and I got all the granite blocks squared and leveled on the gravel pad, we fit hardware cloth over the ventilation spacing between the blocks to keep critters out. This cloth was bent around top and bottom of the blocks and glued in place with construction adhesive to ensure there was no way anything was getting under there.
We laid six-mil plastic over the gravel inside the foundation to seal off future moisture release. Then, on top of the granite we half lapped a pressure-treated 2x6 to overhang the blocks by 1” on all sides. The conventional TJI deck was then constructed on top of that. These man-made joists are unpleasant to work with but are functional and quick to assemble. With the I-beams in place, we cut ½” plywood to lay between them. These were then screwed to the beams. On top of that, we laid 2” blue foam that we then sealed with Great Stuff spray foam to close up air gaps. I’ve seen this blue foam/Great Stuff method called “poor man’s spray foam”.
With the blue foam installed, we laid the subfloor. After applying a bead of construction adhesive, we screwed 3/4” Advantech down to the framing. We were happy to find that at every stage of the process things turned out square. We joked that all our mistakes must have compounded to cancel each other out.
Despite the purist strain some of us may have, I think we made the right choice. With this floating block foundation, it seemed best to avoid a central support point and so, to be able to span the 25’ of the deck without sagging, TJI joists made the most sense. Although not particularly fun to do or interesting to discuss at length, this deck system will give us a solid, draft-free floor. Once it’s buried in top floor and exterior sheathing I’ll never have to look at it again. I’ll just enjoy the benefits of its performance for the rest of my life.
Luke and part of his crew arrived from Vermont this afternoon with the final trailer loads of the frame. We spent time getting to know each other and they looked over the site before heading off to their rental house. They’ll be spending tomorrow putting a few finishing touches on the frame’s sills in preparation for Monday. Then, over the following few days, it all goes up.