how much weight can a concrete foundation handle?

[alton]

In my slab the rebar was laid on 12" or 18" centers running vertical and horizontal, the main beams where 24" deep. I have seen beams 3' deep..
Some contractors in San Antonio do not use rebar, they use cables to hold the slab together. I do not think this is a trade secret but a large retail store does not have any steel in there slabs. They put steel in there outside beams and of course in the concrete holding up the columns.

The more you spread out the weight the less pressure on the slab.

[grouch]

Be thankful your in SA not DFW. The foundations in DFW have steel tesion cables through them and rebar. The steel cables are there to hold the foundation together if it cracks due to earth movement. The builder of my house in Keller have to come back for several homes including mine and pier the foundation which is jacking your house up to level and driving steel piers all the way down to bedrock under the foundation, this was 35ft. in my case. In SA especially on the north side there is so much rock so close to the surface I don't think the foundations are going to move nearly as much. I'm sure there are areas with foundation problems here as I have seen foundation repair companies in buisness. The clay soil in DFW can contract 5x the size in relation to soil moisure content but as I have noticed there is not much topsoil here and if your house is on rock it doesn't move much.

[rrasco]

Oh, they move here. There are lots of foundation repair companies around here and it's not cheap. My foundation needs to be fixed (pier reinforcement), my dad has had his fixed, and I know several others who have had repairs. This summer has been especially difficult due to the drought, as the soil dries out, it compacts and the foundation settles, often causing damage to the house, although, mostly cosmetic. Cracked/lifting tiles, cracks in drywall and ceiling, doors sticking/not closing, etc. That's why they say to water around your foundation with a soaker hose, it get's difficult though when it's as dry as it was this year.