Expansive soil issues

by Cole Kelly
(Los Angeles, Calif.)

Hi Susan-

I want to build a 42" high, curved, patio wall (35' long-achieving an approximate 90 degrees), to enclose a front yard Patio. And I'd like to use used bricks for the floor of the Patio (dry laid). What I'm concerned about is the clay, expansive soil the wall and bricks will sit on. Any ideas on special footings for walls built on expansive soils? I know it's not very tall; but I just want to do all I can to keep it from cracking. Also, considering the dry laid bricks, is there any tricks to consider in the base material that will aid in this regard? Thank You. Cole Kelly.

ANSWER

Hi Cole,
I can give you my thoughts on this matter which basically are just that. However, I would strongly suggest you contact a structural engineer who will be able to advise you better than I, particularly if they have dealt with expansive soil issues.

I have never worked with these types of soils. However, I would guess that both the patio and the wall would be better off dry laid. You did not mention what the wall would be built out of. Being that the patio is brick, are you considering brick? This can't be dry laid so another paving material would be a better option, such as natural stone.

The trick to success is most likely in the base (for the patio and also the wall).

Regarding the patio, the first patio layer is stone. On top of that would be a layer of sand or stonedust, then the brick. In your case, one thought might be to replace the soil beneath the patio. This would have to be tamped in lifts since it has now been disturbed. Then you might make the layer of stone extra deep. See my page on Building A Patio for specs on building a standard patio.

Regarding the wall, the same might apply...replace the soil in a large area and have a deeper stone base.

As far as footings go for a mortared wall, I really don't know. Again a structural engineer is your best bet. Make a few calls and see if they can give you some information. You may have them proceed further to design your hardscape from a structural perspective, but at least this will give you a start.

Susan