Dirt work for pad.

[myershub4]

I live down here in Texas close to Houston, we have a cleared grassy area we want to build on but when it rains it turns mushy. We are going to scrape the ground and build a pad. My question is what kind of dirt is best? Ive read its not good to build on clay but down here they build on a sand-clay mix or so they say it is. Ive read you should build on a layer of gravel then a layer of sand. What to do? :?

[Rich]

The advice about not building on clay is typically a good one. It's not that it can't be done it's just that the expansiveness of the soil needs to be taken into account with caissons and a structural slab or caissons with a hanging floor, etc.
Besides that I've poured slabs on undisturbed earth, compacted earth, sand, gravel, etc..etc. Most any of these substrates will prove suitable. Probably the best way though is a 4" layer of gravel. Sand - although it sounds like a good thing to pour on top of - it's not all that great without a barrier. The problem with sand is that it absorbs moisture until it's saturated - then it will allow water to pass through. So if you do you use sand I would suggest putting a layer of plastic over top of it and pour on that. Is what happens is the sand will pull all the moisture out of the concrete well before it has a chance to go through a normal curing cycle. Is what that does is creates a "brittle" concrete.
Hope that helps.