footing substrate

[jgerstein]

I am helping a friend constructing a two story garage in Virginia and we are running into inspection difficulties. The minumim depth need for the footings was 2'6" and the trench were dug about 4 feet below what will be the finished grade. The soil underneath is clay which has since become saturated with groundwater. My solution was to put course gravel compacted into the trenches getting the bottom of the footing above the water table. In most of the footings this has provided a good base but there is still water in about 20' feet of trench making it unsuitable to pour concrete. The inspector has said to get the soils engineer back out and he is telling my friend to get all of the gravel out of the trenchs so he can the soil. My solution is to put another 6-12" of coarse gravel compacted. I believe digging down further will ultimately hurt the foundation. Is there a section in building code which describes alternatives for this and any thoughts.

 

[Focht3]

Ouch! It sounds like you are trying to go around the geotechnical engineer. Why? Is your engineering seal on this work?



This is a case where your friend should have scheduled a visit by the geotechnical engineer when he first encountered water, not after one of you made a geotechnical engineering decision, modified the engineering design, constructed your modified foundation, called for an inspection, and only then did the inspector make the correct call - contact the real expert.

If this were my project, I'd have your friend do the very same thing - have him remove the gravel, etc. so I could see what's going on. Do as the geotechnical engineer asks. Cheerfully, with apologies for your foolishness. This time, fill the excess hole with concrete - or whatever the geotechnical engineer advises you to do. And advise your friend to rent a small backhoe or trencher (if he is doing the work by hand) so that he can perform the work quickly. Time is just as important as depth and the presence of water in the stability of a (shallow) excavation.

Most of all, both of you should learn from the experience.