Depth of Footers for housing?

Question

I've spent the past two days searching the internet to no avail


How do I find out how deep to make the footers for a house? Slab-en-grade concrete foundation. According to my teacher, the footers have to be below the frostline for whereever you "build" the house. Im looking at the pacific northwest, most likely suburban areas.

So, how deep do I make the footers or how can I find out how deep to make them?

Answer 1

The footers must carry the load of the exterior walls, and therefore depend on whether the building is single story, two story, etc. It will also depend on the type of soil you have. They should extend below the frost line, or you will get lifting (and cracking) over the years.

If this is for residential construction where engineering is not required (one or two stories), your local building department may be able to provide guidelines for the footing design, including rebar placement.

For the slab, I recommend that you use rebar instead of wire mesh. It only costs a little bit more, but is much more effective in controlling cracking. Number 3 rebar (3/8") on 12" centers should do.

Answer 2

The frost line in much of the pacific northwest is fairly shallow, so your footers would probably be deep enough already to get below the frost line. You should be able to find some data from local code requirements. I would think in this region a bigger concern would be the soil conditions with the amount of rain they get.

Answer 3

As you pointed out, it depends on where the land is. You need to call a nearby city's building department, maybe they could tell you the requirements.

Answer 4

In some locations local code sets the depth.

The US weather service should also have this info.

Try this:
http://www.ncdc.noaa.gov/oa/climate/freezefrost/freezefrost.pdf

Answer 5

it depends on the soil
its better to ask ur neighbours or look in the library in the aci code it classifeis soil types
i guess its about 1.5-2 m