Saturday, September 22, 2007

Steel

Interesting comparison of the steel used in my brother's recently-built slab house foundation in Albuquerque and the steel required by my upcoming wall. The house uses wire mesh while the wall uses rebar. Concrete really doesn't like to be put in tension.

Here's the wall schematic, and here's the house:

Friday, September 21, 2007

Geotech non gratis

I got a bill from the geotech for $350 -- two hours of work to

- check out the back yard and
- write a memorandum saying my yard is built on a landslide of clay just waiting to turn to mud and
- take on legal liability for the work done subsequently based on his opinion

so I can't fault the guy.

Expedite!

The first rain of the season came early yesterday, but it was impetus for us to get moving smartly on the wall project lest the excavation succumb to gravity and water. I've hired a contractor with some experience building this sort of wall, and while it won't be cheap it won't be ridiculously expensive either, about $30K including the drain to the street and ancillary work. A bit more than half of that is labor cost. The wall will have 5/8" rebar every 12" horizontally and vertically, so it should stop the mud just fine.

Here are pictures of a similar wall form system that the contractor built for another client. What's interesting about this is the wall is poured all at once, foundation plus vertical. This is accomplished by suspending the vertical forms from hangers that run from the hillside down to inside the walled area. The forms themselves are made of 2x12 douglas fir with 2x4 walers (backing stiffeners).





We start work on Monday.