Thread: Vent pipe in attic

The owner ran this plumbing vent up, over and down, so that he could install pull down stairs. I don't think this is a problem, however I thought I would ask to be sure.

Rich

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By up, over and down I assume that you mean he created an upside down u (or an n) with the vent pipes. If so, this is wrong. It will trap rain water and condensate in the section that goes up and through the roof.


BTW....

I always write up those cheap pull down stairs as low quality and caution the client about relying on them to enter/exit the attic safely. I also list them as a breach of the fire separation between the home and garage if installed in the garage, unless provisions have been made to resist fire.

It does not go through the roof and it terminates into a main vent.
Rich

Vent is still wrong, needs to slope and not trap condensation.

A vent needs to "vent".

That's a large trap, that is not going to "vent" (at least not properly).

He would have been better off (and it would have been easier and cheaper - less pipe) to 'go around'. Sloping uphill as he went 'around'.

Like everyone else has said-- wrong. Everything must slope back toward the sewer line.

Lost my head today. 1/4" per foot back to the main drain/vent.
Rich

Originally Posted by Richard Roshak

Lost my head today. 1/4" per foot back to the main drain/vent.
Rich

That is the minimum for waste piping but as long as there is some slope in the vent piping, I wouldn't get excited. You don't have to worry about solids settling out in the vent, unless it is a wet vent in which case it becomes waste piping.

If both Horizontal pipes are slopped in the direction that they would drain, then this configuration will work. The pipe size though is another issue. The configuration as shown looks like an "island vent", without a sink draining into it.

Tony: I don't believe the photo shows two vents flowing away from eachother that tie in above where we can see adn then shoot out the roof. We're looking at what used to be one long horizontal vent running near the floor, that the homeowner jogged up out of his way so they could put in an access to the attic, so both horizontal pipes are sloped the same way.

Originally Posted by Richard Roshak

It does not go through the roof and it terminates into a main vent.
Rich

If one side ties into a vent TEE and the other side is the upper section of a common or individual vent then both sides have to drain to a stack, with the right grade of course.

Originally Posted by Tony Watson

If The configuration as shown looks like an "island vent", without a sink draining into it.

Tony,

Think of it as a "high loop" instead of an "island vent".

The island vent is tied back down to the drain, creating a vent path.

That is a high loop, not tied back down to anything, creating a trap (inverted trap, which traps air).

Not to change the subject... Were the trusses design for attic storage? If he did this as an after thought, they're most likely not. Looks like a lot of "stuff" up there, along with the extra plywood load. Attics with limited storage are required to have live load of 20 psf applied to the bottom cord. Something you may want to note.

Originally Posted by Door Guy

Not to change the subject... Were the trusses design for attic storage? If he did this as an after thought, they're most likely not. Looks like a lot of "stuff" up there, along with the extra plywood load. Attics with limited storage are required to have live load of 20 psf applied to the bottom cord. Something you may want to note.

And, if read notes b and g, you would also have noted:
- b. Attics without storage are those where the maximum clear height between joist and rafter is less than 42 inches, or where there are not two or more adjacent trusses with the same web configuration capable of containing a rectangle 42 inches high by 2 feet wide, or greater, located within the plane of the truss. For attics without storage, this live load need not be assumed to act concurrently with any other live load requirements.
- g. For attics with limited storage and constructed with trusses, this live load need be applied only to those portions of the bottom chord where there are two or more adjacent trusses with the same web configuration capable of containing a rectangle 42 inches high or greater by 2 feet wide or greater, located within the plane of the truss. The rectangle shall fit between the top of the bottom chord and the bottom of any other truss member, provided that each of the following criteria is met:
- - 1. The attic area is accessible by a pull-down stairway or framed opening in accordance with Section R807.1; and
- - 2. The truss has a bottom chord pitch less than 2:12.

- R502.3.1 Sleeping areas and attic joists. Table R502.3.1(1) shall be used to determine the maximum allowable span of floor joists that support sleeping areas and attics that are accessed by means of a fixed stairway in accordance with Section R311.5 provided that the design live load does not exceed 30 psf (1.44 kPa) and the design dead load does not exceed 20 psf (0.96 kPa). The allowable span of ceiling joists that support attics used for limited storage or no storage shall be determined in accordance with Section R802.4.
- R502.3.2 Other floor joists. Table R502.3.1(2) shall be used to determine the maximum allowable span of floor joists that support all other areas of the building, other than sleeping rooms and attics, provided that the design live load does not exceed 40 psf (1.92 kPa) and the design dead load does not exceed 20 psf (0.96 kPa).

The trusses in the photo, then, would most likely have been designed for a live load of either 30 psf or 40 psf ... because they are definitely not designed for "limited storage".

Originally Posted by Door Guy

Attics with limited storage are required to have live load of 20 psf applied to the bottom cord. Something you may want to note.

Really? You have to apply the live load, not just design for it?