Foundational knowledge

The excavators removed the foundation today; apparently the stem wall was in such poor shape that you could hit it with a hammer and break bits off, so I guess the heavy machinery made short work of it. I’m glad, honestly, that we won’t be in a situation of wondering if the old wall was enough; it definitely wasn’t. Imagine the rage if we’d spent $20,000 on waterproofing and then the basement was still not properly sealed…
This process has taught me things I never realised I might need to know. In particular, let’s talk about foundations. There’s roughly three ways to build a foundation:

A monolithic slab. You pour a great big piece of concrete, strengthened with metal mesh or rebar, and then your house sits on top of that. Seems to be used for sheds and garages, less so for houses (I’m guessing because it has structural implications, and you don’t get a basement.)

Stem walls. The house rests on a perimeter wall. The spec for ours is an 8" wide concrete wall that comes up above the level of the yard, and goes down to the floor level of the basement. Then that is on a footing that’s about 12" wide, with the whole thing forming an inverted T shape. Again, there’s steel in there for reinforcement (or not, if you’re talking the wall our house sat on for a century). There was also no footings on the old wall, and again, one might be amazed that a structure like this survived in an earthquake zone like Seattle.

To confuse things, our house also had a slab, but that doesn’t count as a foundation because it didn’t provide a structural part of the house; it was just concrete poured in to make a floor, rather than just dirt. Given the cracks in it, it didn’t even do that job very well.

And finally, you have just posts on concrete blocks, which is what the front of the house was supported by. They really did do things differently back in the old days.

I spoke with Grant, the huge New Zealander who owns the excavation company. He asked about our plans to install radiant heat (something he regrets for his own house) and a heat pump (which he thinks is a good thing). It’s interesting who you end up trusting; implicitly, you have to have some trust for the man who’s driving a bulldozer through the bottom of your house, and I got a less equivocal answer from him than from structural engineers ("oh, the general contractor will have to figure it out") … Make of that what you will.

Tomorrow they start the pour: the concrete sub will have the footings done in a day, I think, and then on to the new stem walls, and then the house comes back down, the cribs that the house rests on will be removed, and the remainder of the old slab is demolished before the new one is laid. I have the day off so we’re going to hide in the Olympic Peninsula and visit the cider farm. It’s going to be a good week.