Building Setback from an Existing Retaining Wall 1

[00Z]

I posted this in the Foundation Engineering forum, but thought I would try it here too. I have a client that would like to build a new garage 2 feet back from an existing 4 foot tall retaining wall.

Since I have no information on the existing wall other than that it is a "block wall with pins connecting the blocks together" I want to avoid placing an addition surcharge on the wall from the building.

Currently the footing is proposed to be 2 feet deep. I am concerned that this will still place a surcharge on the the block wall. Am I being to cautious. Would you design the footing to be 3 feet deep, 4 feet?

See the attached sketch, and thanks in advance for your input. A couple of other quick points, there is no soils report, the block wall has no footing, the garage is single story and it is a gable end wall so the load from the wall is only around 205 plf.

 

[EngineeringEric]

Your quote makes me think this wall is more like the attached photo of block wall retaining wall. These are unreinforced and simple. I would put my footings like the wall was not there, my footings will be to the bottom of the adjacent grade (4').

If the wall was gone, i would not want my footing on a 1:1 slope of soil like you have drawn. Assume that wall can not take any load, including the load of your slab surcharge if applicable.

 

[00Z]

Thanks for the quick response. I appreciate it!

 

[BAretired]

In Alberta, the usual practice would be to support the structure on piles and grade beams with void former under the grade beams to prevent frost heave. The piles could be drilled and filled with concrete or helical steel piles. Both are commonly used in my area.

BA