Main Waste under footing? - InspectionNews

John Thompson · #1 (**permalink**) 05-12-2008, 10:20 AM

I recently ran across a PVC waste line that exited the structure directly undernieth the footing, in a perpendicular fashion. Is this allowed. I was under the impression that the "zone of compresson" under a footing could not be compromised. Additionally, the IRC [2604.4] states no trenches [parallel to] to bottom of bearing footing within 45 degrees. This situation is not parallel to, but my client wants to know what code is in question.

Jerry Peck · #2 (**permalink**) 05-12-2008, 07:35 PM

Quote:

Originally Posted by John Thompson

I recently ran across a PVC waste line that exited the structure directly undernieth the footing, in a perpendicular fashion. Is this allowed.

Yes, it is allowed, but ...

From the 2006 IRC. (underlining is mine)

- P2603.5 Pipes through footings or foundation walls. A

ny pipe that passes under a footing or through a foundation wall shall be provided with a relieving arch; or there shall be built into the masonry wall a pipe sleeve two pipe sizes greater than the pipe passing through.

Passing through a foundation wall - a relieving arch or a sleeve two pipe sizes larger.

Passing under a footing - a relieving arch.

Joshua Hardesty · #3 (**permalink**) 05-13-2008, 10:54 PM

Jerry,

How exactly is "a relieving arch" defined?

brian schmitt · #4 (**permalink**) 05-14-2008, 09:42 AM

dirt over the pipe in an arched style works for me!

Jerry Peck · #5 (**permalink**) 05-14-2008, 01:41 PM

Quote:

Originally Posted by Joshua Hardesty

How exactly is "a relieving arch" defined?

Joshua,

"dirt over the pipe in an arched style works for me!" is not correct.

The footing needs to be designed to arch up and over the pipe, with the steel in the footing, in such a way as to transfer the load "above" the pipe location to the sides of the pipe location, so that there is "no load" directly on the footing pressing vertically down toward the pipe.

Joshua Hardesty · #6 (**permalink**) 05-14-2008, 04:10 PM

Jerry,

So from your description, a relieving arch will never be added after the footing is already there, it's got to be engineered into the system when it's built.

How'bout this then: When a basement is built with a poured cement wall, and is core drilled, does that still need a sleeve?

And furthermore, I have a question about the material of said sleeve. I know its supposed to be two pipe sizes larger than the pipe itself, so if I have to run 1/2" pex through a wall, how much protection is that 1" pex really going to offer?

Jim Robinson · #7 (**permalink**) 05-14-2008, 04:16 PM

I was under the impression that the sleeve was for abrasion protection, not compression. I could be wrong.

Joshua Hardesty · #8 (**permalink**) 05-14-2008, 04:20 PM

If that is indeed the case, then does the corrugated pipe that is sometimes put into foundations/footings (instead of coredrilling afterward) provide adequate protection? (assuming it's properly sized)

Jerry Peck · #9 (**permalink**) 05-14-2008, 04:39 PM

Quote:

Originally Posted by Joshua Hardesty

Jerry,

So from your description, a relieving arch will never be added after the footing is already there, it's got to be engineered into the system when it's built.

Correct.

Quote:

How'bout this then: When a basement is built with a poured cement wall, and is core drilled, does that still need a sleeve?

Now you are mixing terms.

We *were* talking about going "under footings", now, though, we *are* talking about going "through foundation walls" ... and the code covers that - sleeve it with a sleeve two sizes larger.

Quote:

And furthermore, I have a question about the material of said sleeve. I know its supposed to be two pipe sizes larger than the pipe itself, so if I have to run 1/2" pex through a wall, how much protection is that 1" pex really going to offer?

I don't know about using PEX as a sleeve, but, for the moment, let's say it is okay.

That PEX is simply there to make sure that the pipe does not do three things: 1) abrade or have dissimilar material contact; 2) allows for the sleeved pipe to be totally free of pressures on the foundation wall' 3) allows for expansion and contraction of the sleeved pipe.

brian schmitt · #10 (**permalink**) 05-14-2008, 04:50 PM

jerry,
your statement about requiring a design for running a building drain under a footing is special. pay an engineer to say how to accomplish something done everyday as standard practice? the codes require protection of piping and dirt over the pipe provides adequate protection. maybe there is a reason that you feel engineering is required that i am not aware of ?

Jerry Peck · #11 (**permalink**) 05-14-2008, 05:37 PM

Quote:

Originally Posted by brian schmitt

your statement about requiring a design for running a building drain under a footing is special. pay an engineer to say how to accomplish something done everyday as standard practice?

It may be "done everyday", but then so is "multiple tapping" terminals in electrical panels ... does NOT make it correct, though, does it (just because it is "done everyday").

Quote:

the codes require protection of piping and dirt over the pipe provides adequate protection.

Brian, I suggest you read the wording in the code, then post it here, showing us which part says that.

Quote:

maybe there is a reason that you feel engineering is required that i am not aware of ?

"that i am not aware of ?"

Yep, it's in the code.

Jerry Peck · #12 (**permalink**) 05-14-2008, 05:43 PM

Joshua,

Attached is one structural engineers design for when a pipe goes through a footing. This one relieves the pressure "around" the pipe as the pipe actually "goes through the footing" (not under it, and not through a foundation wall). The "relieving arch" effect, though, is required so that no load from above is placed on the pipe.

There are other design which are more like 'arches' for when the pipe goes "under" the footing (instead of through the footing as in the attached).

Jerry Peck · #13 (**permalink**) 05-14-2008, 05:50 PM

From the Commentary on the IRC.
- P2603.5 Pipes through footings or foundation walls. Any pipe that passes under a footing or through a foundation wall shall be provided with a relieving arch; or there shall be built into the masonry wall a pipe sleeve two pipe sizes greater than the pipe passing through.

(Commentary)

❖

Any pipe installed within or under a footing or foundation wall must be protected structurally from any transferred loading from the foundation wall or footing. A relieving arch or a pipe sleeve can be used to provide this protection. Where a sleeve is used, it must be two pipe sizes larger than the enclosed pipe. This space will allow for differential movement of the pipe. See Commentary Figure P2603.5.

Attached as drawings from the Commentary.

Jerry Peck · #14 (**permalink**) 05-14-2008, 06:04 PM

From the Commentary in my previous post:

"A relieving arch or a pipe sleeve can be used to provide this protection."

That, to me, means that the pipe used for the sleeve (used to provide the protection intended - "must be protected structurally from any transferred loading from the foundation wall or footing" - would thus need to be at least sch 40 steel pipe.

Even PVC, being must stronger than PEX in providing protection, *will not* protect from the loads being described.

brian schmitt · #15 (**permalink**) 05-15-2008, 08:11 AM

jerry,
pipe thru a wall or footing is a prescriptive approach clearly defined in the code. under a footing was not shown in your rather impressive cut and paste display of commentary which is not code in the enforcement world. you continue to have your take and i will have mine! i enjoy the opinions of others and learn from them often....but not this time

Jerry Peck · #16 (**permalink**) 05-15-2008, 02:55 PM

Quote:

Originally Posted by brian schmitt

pipe thru a wall or footing is a prescriptive approach clearly defined in the code. under a footing was not shown

Brian,

Not sure what part of (underlining is mine) ...

Quote:

Originally Posted by Jerry Peck

- P2603.5 Pipes through footings or foundation walls. Any pipe that passes under a footing or through a foundation wall shall be provided with a relieving arch; ...

... you don't understand.

brian schmitt · #17 (**permalink**) 05-15-2008, 04:01 PM

jerry,
what is a relieving arch comprised of. is there a definition of how to make one and what type of material is it made of? dirt,concrete,wood? is there a definition in the i.p.c.? we still use the u.p.c. and it simply calls for sleeving or protection of piping thru or under walls and the commentary(not code) just shows a pipe run thru the dirt under the footing. so jerry i don't understand why a relieving arch can,t be made of dirt when a pipe is run say 12"s below the bottom of the footing?splain it to me

Jerry Peck · #18 (**permalink**) 05-15-2008, 04:15 PM

Quote:

Originally Posted by brian schmitt

i don't understand why a relieving arch can,t be made of dirt when a pipe is run say 12"s below the bottom of the footing?splain it to me

Brian,

I will *try to* 'splain it to you where you can udderstan' it.

"why a relieving arch can,t be made of dirt when a pipe is run say 12"s below the bottom of the footing?"

Q. Okay, first, what is the footing bearing on?

A. The soil beneath that footing.

Q. What bears on that footing which is bearing on that soil?

A. The entire load of the house above that part of the footing, and, if under a load bearing column, more of the structure's load that what is just above that footing area.

Q. What does that soil below the footing bear on?

A. More soil beneath that soil.

Q. What would happen is that soil beneath the soil beneath the footing were removed, or allowed to collapse?

A. The soil above would cave in to the void created by such collapse.

Q. What would happen to the footing above when that happens?

A. The footing above would not have its designed soil bearing support and could shift, allowing the structure to shift.

Q. What if the structure did not shift and the only thing which happened was that collapse of the soil beneath the soil supporting the footing?

A. The pipe in that collapsed soil has collapsed due to the load on it from above, and, while the structure may not have suffered any noticeable effect, the collapsed pipe is now blocked with soil.

Q. What does a blocked sewer pipe cause?

A. Sewers to back up and cause your cup to runneth over.

And your bowl too.

brian schmitt · #19 (**permalink**) 05-15-2008, 04:58 PM

jerry,
a 3 or 4" pipe in the dirt under a concrete foundation and the concrete will collapse and will kill thousands? put down the pipe! i think a foundation can span a few inches even without rebar in it. you are going to get a migrane trying to convince me on this one. and what is a relieving arch made of o wise one?