CMU Crawl Space Foundation with Central Built-Up Girder Beam
We are working on a small build – small cabin/ADU, doing a mix of DIY and hiring things out. We hired out the block wall crawl space foundation with specification that we are putting a 3-ply 2×10 built-up girder beam down the center, 24′ total length. We asked the mason to construct/cut pockets in the CMU for us to rest the girder beam.
Unbeknownst to us, he ended up cutting completely through the block through to the outside rather than there just being a ‘pocket’ cut out that is only visible from inside the crawl space. See photo. (Yes there are 2 interior piers for the girder beam – overkill for such a small structure, we know. The point of this question is specifically the end pockets…)
Eventually we want to put some type of stone veneer over the block wall. But initially now wondering how to handle this notch in the wall? Do we just use pressure treated 2x10s for the built-up beam, and extend the girder beam to be flush with exterior wall? How should we air seal/moisture seal/insulate around this space?
It will be a conditioned unvented crawl with interior foam panel insulation and a dehumidifier. Our county code requirement is IRC 2018.
Thanks for your input.
Replies
The CMUs are relatively moisture permeable, so the exposed end-grain of the beam isn't much more of a liability than end grain next to the outer wall of the CMU. I'd just saturate any cut ends of the beam with preservative and wrap them in some sort of impermeable peel'n'pray membrane (which you should do anyway.)
If you need the excised outer wall of the CMU, say for temporary cosmetic reasons or stone veneer substrate, it could be held in place with landscape adhesive (e.g., PL500) and mortar.
Rather than working around the situation, could you remove the cut blocks and replace them cut the way you want? Could you ask the mason to come back and redo those blocks?