Minimum dimensions for powder room under stairs?

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Old 04-19-10, 03:25 PM
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Minimum dimensions for powder room under stairs?

Hi,

As our renovation project nears completion, we're installing a main staircase in our 100-year-old house to replace the one that was ripped out 40 years ago. We'd like to put a powder room under the stairs, but there's not a lot of room there.

We'd put the door (opening outward) on the side of the stairs, with the sink under the high part of the stairs and the toilet under the low part.

I know the powder room has to be at least 30" wide. Is there a minimum ceiling height under the toilet? Any other heights or clearances we need to worry about?

Thanks!
 
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Old 04-19-10, 08:12 PM
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A toilet needs 30" of width minimum -- 15" on each side from the center line of the bowl. It also needs 30" from the front of the bowl to the nearest object. I'm not sure what code is as far as height, but I wouldn't want anything less than 7 ft. from the floor to the ceiling where it's sitting.
 
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Old 04-20-10, 06:10 PM
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Have you tried making a scale drawing?, or made a layout drawing on the floor, per Lefty's specs?

Have you worked out provisions for the vent stack?
 
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Old 04-22-10, 09:42 AM
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The 30" width is no problem. But there certainly won't be a 7' ceiling anywhere under this part of the staircase, and it'll be even lower under the toilet.

About the vent stack... there was a full bathroom there which we ripped out to make room for the staircase. There was no vent stack in that bathroom. The horizontal main stack is right below where the staircase will be. Would a vent stack be required there?
 
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Old 04-22-10, 05:15 PM
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You sure there was no vent stack for that bathroom?

What other plumbing was located near that bathroom? Like is there a kitchen back to back with where the bathroom was? If yes, is the vent stack in that wall common with the kitchen? Have you looked up at the roof and see no vent stack anywhere near that area? Or how else do you know there is not a vent stack?

About the toilet - this is obvious - but consider the ramifications if a guest uses that toilet, stands up off the pot, and sprains his neck on the ceiling.
 
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Old 04-22-10, 08:08 PM
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demolition_man,

Trust me on this one -- if there used to be a bathroom there, it HAD plumbing vents for the drains. Whether they were removed or not when the bathroom was, I don't know, but I would tend to doubt it. If there is plumbing backed up into an adjacent wall, you can probably tie into that if need be.

As far as the ceiling height above the toilet, do this. Take a kitchen chair and set it where the toilet will be. Now sit on the chair and tell me what you think. Then stand up and see if you change your mind!!
 
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Old 04-28-10, 01:22 PM
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Thanks lefty. About the vent stack -- I demo'd the bathroom myself a few weeks ago, and I can tell you there was no separate vent. The bathroom was basically right above the main stack, which runs horizontally halfway through the basement, then turns and goes up parallel to the chimney and through the roof, providing the only vent. The bathroom of course had drains for the toilet, sink and bathtub all hooking into the main stack, and that was really it.

Keep in mind the house is 100 years old, and the bathroom I ripped out was put in 40 years ago, so maybe the codes were different then?


If there was no separate vent before, is it a big deal if I don't add one now for the powder room?
 
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Old 05-01-10, 06:12 PM
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I can't speak for what your codes will allow. The height is something that would be addressed in the building code, not the plumbing code.

If this is a remodel job being done with a permit, I think you will have some problems, both with the height, and the vent. By any code, a stack receiving waste from above cannot be the vent for a fixture on the lower level.

Will this all work, yes. So if inspections are not in the picture, you could proceed.

From the standpoint of the future "sellability" of the house, the extra bathroom is a plus, but buyers are also fickle...they will expect it to be "right". I can see some prospective buyer walking in and making nasty comments about the low ceiling in the powder room!!!
 
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Old 05-01-10, 09:22 PM
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demolition_man,

Without a vent on a plumbing drain, that drain will not drain correctly, if at all. Leaving out a vent for the plumbing system IS NOT an option. When we have mentioned "vent" in this thread, we are referring to vents in the plumbing drain and waste system -- NOT a ceiling mounted blower that moves air around.
 
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Old 05-02-10, 07:16 AM
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Originally Posted by lefty View Post
demolition_man,

Without a vent on a plumbing drain, that drain will not drain correctly, if at all. Leaving out a vent for the plumbing system IS NOT an option. When we have mentioned "vent" in this thread, we are referring to vents in the plumbing drain and waste system -- NOT a ceiling mounted blower that moves air around.
That is not really correct. Fixtures like sinks, toilets, tubs are SELF VENTING. They will drain. Not correctly, in that there is a tendency to siphon the trap dry, and THAT is why vents are needed. His toilet will work, but could be subject to gurgling as other waste drains by in the stack.
 
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Old 05-02-10, 10:50 AM
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Thank you guys. As I mentioned, there WAS a bathroom there that we used for a couple of years before I ripped it out, and while the bathtub drain didn't always drain well, we didn't have any problems with gurgling etc.

I want to do this as correctly as possible but a vent in that location is not an easy option - the only wall that goes up from the powder room to the roof is the "common" brick wall between me and my neighbor.

My B&D book talks about AAV's. Is that an option here? I could probably put one in the basement below the powder room pretty easily. As I said, there was definitely no vent before, so hopefully this would be better than nothing?

Thanks.
 
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Old 05-02-10, 11:49 AM
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An A.A. (Studor) valve is an option, but don't place it lower than the level of the P-trap outlet. That would be forming an "S" trap. Under say the vanity, place it immediately after the P-trap inside the cabinet. After the AA valve you can turn the drain down to the basement.

Not sure if AA valves are 'legal' where you're at, but it would certainly be prefferable to an "S" trap or no vent at all.
 
 

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