Plan B

After discovering the state of the wood under the spray foam, and discussing the new situation with the structural engineer; we decided that the only solution that was sure to keep our foundation from crumbling out from underneath us...was to replace it.

Well, not so much replace it, but rather install a new foundation around and in between it. The fact of the matter, is that there is no way to tell whether the wood was structurally sound without removing the foam and testing it. We can't rely on the "sound" test by simply smacking the foam covered wood with a hammer, as was the way of one of the contractors.

Further, with the 20 or so trusses that we inspected, at least 5 of them were completely destroyed or would be deemed structurally unsafe due to their extensive rot. With that sample, we would be looking at about 25% of our foundation unable to support the house. Additionally, with the visible signs throughout the house, it was apparent that this issue was a hidden plague across the entire area of our foundation.

Putting all that together, we decided to essentially build a new foundation throughout. How? That's a good question. The simplest way to explain it is; we would still take Plan A and install crossbeams throughout all the spans. But in addition to the crossbeams, we would add traditional joists in between each truss that is already there. So just imagine 2 trusses (the engineered braces made with triangles) running perpendicular to the crossbeams where the crossbeams cross them at their halfway point. Then imagine taking a 2" x 12" piece of lumber (a "joist") the same length of the trusses. Then we place that joist between the trusses and push it up against the floor with the crossbeam.

Here is a rough sketch of the concept: