3.5' Cover over 12" concrete pipe under footing? 1

[cenc]

Wondering if 3.5' is enough cover over a 12" concrete pipe under a footing? Footing is for single story structure. Soil is mostly clay. The pipe cannot be relocated around the building. Any feedback is appreciated.

 

[RWF7437]

Without knowing whether the pipe is reinforced or not and without knowing what the footing loads are it is impossible to answer. However, this situation is not desirable and is prohibited in most cases by building codes. In the rare cases where it cannot be avoided, sometimes D.I pipe may be allowed or concrete encasement, or sleeving the existing pipe.

Also, you do not say what the 12-inch pipe is for. Is it a sanitary sewer, storm drain, something else?

 

[bpattengale]

Bad idea to run a pipe under a footing, but if it's unavoidable. You run a big risk with a pipe under the footing. I've run concrete pipe below buildings before, but I've always had the structural engineer step the footings down and run the pipe through the footing. It might cost a little more, but it poses less risk if the pipe were to fail.

Think about it this way if the pipe were to fail you could potentially form a sink hole directly under the footing and have a building collapse. With the pipe running through the footing if it fails you're still going to get a sinkhole, but the building will likely still be standing.

Another thing to note is that since the pipe runs under a building you'll likely be governed by the plumbing code and not the usual design standards.