PRE-ENGINEERED BUILDING FOUNDATION

[deereman]

I have a pre-engineered building foundation I am designing. There will be a turndown around the perimeter. This building has an 8" cmu full height wall in some places. In the past i have specified an individual spread footing below the turndown to support the CMU. The contractor has requested the turndown be designed with a ledge to receive the cmu instead of putting in a strip footing below. I can design the footing to support this load, but I was wandering if anyone has had any problems with a foundation like this that I may not be accounting for?

 

[msquared48]

I have no problem with the ledge, but, due to the dead load of the CMU, I would extend the slab to frost under the CMU to avoid frost action and heave.

Technically, the CMU wall is probably not a bearing wall, but I would treat it as such due to it's own dead load.

Mike McCann
McCann Engineering

 

[DaveAtkins]

I am not sure what you mean by a "ledge". I would just use a grade beam and be done with it. If insulated properly, the problems mentioned by Mike go away (you run rigid insulation down the outside face of the grade beam, and then extend the insulation four feet or so horizontally outward away from the building).

DaveAtkins

 

[abusementpark]

Like Dave said, I would seal the perimeter with grade beam and be done with it. Just make the grade beam wide enough so you don't exceed the allowable bearing pressure. I am assuming the ledge you are referring to is a standard 2"x8" dap to receive the CMU wall.