Continuous Footing in expansive soils

[msdmoney]

I am designing a residential foundation on potentially expansive soils. The geotech report gives recommendations for conventional continuous and spread footings, and also gives a differential deflection value of 1" in 30 ft. Is the typical method of analysis for this condition to compute the moments for the imposed displacement due to differential deflection and design the reinforcing for that moment. The required amount of reinforcing is getting above what is typical for the area, at least for residential. Makes me think that there might be a better approach.

 

[XR250]

Can you dig thru the plastic clay down to better material?

 

[jayrod12]

Well my argument would be 1" in 30 ft would be the upper bound of the differential settlement, which is L/360. Depending on the construction of the residence above, it can likely accommodate this amount of movement.

We put strip footings on expansive clays all the time here for residential. More and more homes are migrating towards piles but budget sensitive builders still do footings and they generally perform acceptably.