Drainage Pipe Through Footing

[Wandering Wallaby]

Hello Everyone. The contractor on several of my projects would like a typical detail for a situation where a drainage pipe exits the crawlspace of a new residence through the footing. These projects are typically 2-3 story light framed structures. The footings are typically 8" thick by 16" wide with bottom at frost line at 18" below grade, and 8" concrete stem walls above. The sleeve is 6" pvc and is bottom flush with the bottom of the footing, leaving 2" of concrete above the sleeve. Ideally, this would penetrate through the wall above the footing or maybe in a trench below the footing backfilled with slurry, but those are not options. I have attached details of 3 options that I would appreciate feedback on from you all if possible.

Option 1 thickens the footing and bends the reinforcing below the pipe, essentially continuing the footing below the pipe. Then the top of the footing is increased in depth acting as a 4" reinforced slab above the pipe. This would involve cutting into their wood forms for the stemwall for a typical 8" thick footing, however sometimes the footing are required to be 10" thick (usually for lateral overturning resistance) which would negate cutting into the form.

Option 2 keeps the bottom flush but thickens the footing and reinforcing up over the pipe, but again this involves cutting even more into the wall formwork.

Option 3 uses the concrete stem wall above as a deep beam to span the area, and continues the footing and reinforcing below the pipe for continuity. This appears to eliminate the need to cut the stem formwork but leaves only 2" of concrete cover over the pipe on either side of the stem wall (which can be 12" wide on either side of the stem when the footing width is 2'-8" at times). I'm assuming it will crack at those areas so I wonder how reasonable it would be to have them thicken those areas on either side of the stem by blocking out the middle area where the stem wall formwork will go (basically a small short section of removeable formwork to block out the stem wall and allow the footing to thicken on either side. Perhaps I'm over thinking this one.

Thanks in advance for any input.

 

[HTURKAK]

I would prefer option 3...

But make sure that the fill ht above the drainage pipe is ≥ 2/3 ( frost depth )=12"

If the pipe is brittle material ,( e.g. vitrified clay , conc...) provide short pieces at both sides of crossing ..

 

[TigerGuy]

What about stepping the footing down, below the drain pipe, and sleeving the pipe through the stem wall. It will take extra reinforcement around the opening, but I would rather have a pipe through a wall than footing.

 

[Wandering Wallaby]

Hi, thanks for the replies. Stepping the footing sounds great structurally but I am trying to limit the amount of formwork cutting/notching/adding, and stepping the footing down would involve a modified form at the dropped stem location. I created a new detail which is a modified version of Detail 3 but with the raised top of footing on either side of the stem for concrete coverage for the reinforcement above the pipe. It involves only a few scrap 2x for forms. I suppose I'll let the contractor decide if they would rather step the footing below or build to this detail. Either one seems fine structurally; it's more of a means and methods item for them to consider.

 

[SlideRuleEra]

1) Perhaps I'm over thinking this one.

2) ...it's more of a means and methods...

1) Yes.

2) Yes, just specify Option 3 and let the Contractor take it from there.