Bench footing how to determin lateral pressure

[gasma1975]

Hi,

I have a project where I need to lower the basement floor. I want to do a "L" wall in front of the existing foundation wall. If the existing wall carries a linear load of "w" what will be the lateral pressure under that wall which will push on my new "L" bench footing ?

Thank you,

gasma1975

 

[KootK]

1) How high will the step be at this L-wall?

2) How close to the existing wall footing will the back of the L-Wall be?

3) Ideally you'd have a geotechnical engineer advise you on this. Otherwise, perhaps a method like Boussinesq might suit your purposes.

4) When I've done this, I've tried to dodge your question by doing one of the following:

a) Underpinning the existing wall footing which is costly or:

b) Placing the step far enough from the existing wall footing that I'm confident that the L-wall won't see appreciable load from the wall footing.

As you probably know already, these L-walls aren't great for overturning unless they're tied back somehow.

 

[PEinc]

An L-shaped wall for deepening the basement will have overturning and sliding problems unless founded deeper below the proposed basement level. But, a deeper L-shaped wall footing will create more of the same problems. As KootK mentioned, consider underpinning the existing wall. There should be many other ET threads about this same topic.

http://www.PeirceEngineering.com