Three and a half months after digging our initial test pit in the ground in mid-May, we were finally done with excavation and prepped for concrete work.
As our earlier posts discussed, the combination of expansive clay and subsurface water really slowed things down. It was never that we couldn’t dig the wet soil – it was just that digging wet soil is more expensive than digging dry soil due to the additional weight and effort (cleaning sticky clay off of excavator buckets, spraying out trucks). We also wanted to make sure that our crawl space wasn’t going to turn into a swimming pool.
We Got A Moat
The solution ended up being what amounted to a moat dug around the pad, filled with drainpipe and gravel, to move subsurface water around the building pad. That let us start digging.
The moat is the gravel line below the big wall.
The moat also reduced the amount of overdig we needed to do (removing bad dirt just to replace it with good dirt – architectural fill) since the pad would stay drier. That helped recover some of the extra cost of the moat.
Downhill drainage for the moat.
We still needed to bring in a few feet of architectural fill that would serve as the support for the concrete footings. The “good dirt” allows the entire building to float on a pad, which should help resist the tendency of the clay underneath to swell and move when it gets wet.
The timing worked out pretty well too. A day after the geotechnical engineer signed off on our excavation and backfill (deeming it “bomber”), our concrete crew started to move equipment onsite. They’ll handle getting fittings in place, pouring the garage slab, the crawl space, and pouring the back wall, which sets into the hillside about eight feet.
Book Review: Abode
I’m a big fan of white walls and exposed wood. Even so, the design aesthetic in the book Abode: Thoughtful Living with Less is even too “unadorned white walls and bare wood” for me. It also works towards giving design advice, but it’s all pretty light – single paragraph discussions on how to choose art or flooring or whatever. It’s fine, but not a super important book to seek out.