Second-floor bathroom on 2x6 floor joists


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Old 05-15-15, 11:38 PM
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Second-floor bathroom on 2x6 floor joists

Hello folks, I have a bit of a dilemma I'd like your wise counsel on. I'm putting a small 3/4 bath on my second floor, which is actually a large converted attic. The floor up there is framed with 2x6 joists. From what I've read so far, that's not enough vertical room to hide the shower P-trap or the toilet drain. On top of that, the maximum notch OD (Seattle code) is 1/3 the joist depth, so basically the shower and toilet would both have to be in the same bay as the waste stack, which just isn't a feasible configuration.

I can't drop the ceiling below, because it's right above my dining room table. I could sister 2x10s to the joists to give myself enough depth to notch for the drains, but I would lose so much ceiling height that it would make much of the upstairs unusable.

The only solution I can possibly come up with is a macerating toilet. They're expensive, but I've found units that accept inlets from the sink and shower drain, and have an outlet diameter of 3/4". Best of all they don't need gravity, so they don't directly require any plumbing in the floor! The outlet could just disappear into the wall and then run 6' over to the waste stack. However, I assume the shower would have to be significantly raised so the drain could flow into the macerator unit? Or are there inline pumps that work for shower drains?

I've never dealt with anything like this before so whatever intel you're willing to share is much appreciated. Basically, though, my 3 main questions are:
  1. Is the macerating toilet idea a realistic solution?
  2. How high do I have to raise my shower if I assume the shower drain meets the macerator tank 1" from the floor?
  3. Are there drawbacks or other variables I need to be aware of?
 

Last edited by dlukas; 05-15-15 at 11:39 PM. Reason: typo
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Old 05-16-15, 06:06 AM
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First I think you just have to consider that some spaces are not appropriate for installing a bathroom no matter how badly you want to. My first concern would be if the joists were only sized to support the ceiling below or are they enough to also support the weight of finished living space above. How long is the span supported by 2x6 floor joist and what is their spacing? Bathrooms are heavy and you mentioning that it's centered over a dining room makes me think the span could be more than 2x6 can handle.
 
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Old 05-16-15, 01:59 PM
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Whoops, I lied; I had originally planned to put the bathroom above the dining room but since decided to move it. It now will be above the hallway, so the two walls of the bathroom that run perpendicular to the floor joists will be immediately above the downstairs hallway walls. The span is only 5 1/2 ft, and the joists are on 16" centers. It is very sturdy in that spot, as long as I don't go boring through joists.

That said, I do intend to keep the weight down as much as possible (linoleum instead of tile, etc.). I should also mention that this bathroom will only be semi-permanent. In the next 5-7 years we will do a major renovation and everything upstairs will be completely redone.

Sorry for the delayed reply; was solo wrangling a toddler all morning.
 
 

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