I made a trip to the site to watch the excavator break ground. This was April 28. The site was staked and ready to go. Here is the site on the eve of ground breaking.
Archive for May, 2010
I have finished concrete floors in my lower level. I like them quite a lot. However, the area under my chair at my desk had developed some spalling. The spalling is a crumbling of the top surface of the concrete. I believe this is caused by a failure of the surface layer, which is comprised of the concrete “fines” which float to the top during troweling. I suspect that some gritty material gets on the caster of the office chair and with repeated rolling causes some little compression cracks, which then spread. The spalling was not deep, but I suspected it would get worse if I did not deal with it.
Footings are the roughly one-foot thick slabs of concrete on which the foundation walls of the house rest. They are designed to be large enough to distribute the weight of the house onto the excavated soil surface such that the soil does not collapse from the load. As a practical matter they tend to be 20-72 inches wide depending on what part of the house they support. They usually need to be 24-48 inches below the ground surface (depending on region) to be below the frost line.
Placing the footings is a pretty remarkable thing to watch. A crew of 8 (Stone Construction) arrived at 7am and they left around 6pm. With another two hours of work the next morning to strip the forms and pack up, I had completed footings.
This not a fussy construction task. They take a trailer full of lumber and hammer it together in the rough shape they’re after. They pump the forms full of concrete, and then trowel the top surface to a snapped line, which defines the top surface of the footing. The foundation walls are then built on top of these troweled surfaces. The photos tell the story.
This week we got the foundation installed, the damp-proofing and insulation in place, the footing drains installed, and the sub-slab rough plumbing placed. We’re now ready for the lower-level slab to be poured (with the hydronic tubing for heat installed within the slab).
Here are the photos of the foundation and related steps.