P trap too big, I'm stuck,

[Johnfiorello]

Hi! I'm trying to put a bathroom on the third floor (attic) of an older 3 story home. We're running the main drain for the toilet, shower, sink between the walls to the basement where we'll tie in to the existing drain.

The house faces east/west and the floor joists run north/south. The shower drain needs to sit 2 or 3 joists over from the drain to the basement. I just assumed we'd drill through the joists and tie the shower drain into the main drain to the basement but...

When I went to measure to drill I realized the 2" p trap is too tall! With the bottom of the trap resting on the lathe of the downstairs ceiling, the top of the trap is 3/4 of the way over the top of the joist!

I can't really raise the floor of the shower (it's a walk-in style) because of the minimum height for fixtures and the attic ceiling is sloped. I can't trim out an inch off the top of the floor joist, right? And I don't believe either running 1.5" or doing 90s instead of a trap would be up to code... The only thing I can think of is to take out the ceiling of the 2nd floor but it would be in between the kitchen and bath and would be a huge undertaking and ugly.

So, does anyone have any suggestions? I tried to attach 2 pics to help explain what I'm doing.

Thanks for the help!

 

[Terry]

You may have 2x8's or 2x6 floor joists there.
You need 2x10's to do what you intended.

I would not drill across 2x8 floor joists for a 2" pipe. In your case, I would either raise the floor, or drop the plumbing below the ceiling and box it out. You do have to leave structure in place if you expect to add the weight of a tiled shower.

 

[Sponsor]

 

[Johnfiorello]

Yes, they are 2x6 joists.

So, if I shouldn't drill through them with a 2.5" hole for the pipe, how would I get the slope I need to drain? Run above both joists? That would raise the floor of the shower by 6 inches at least...

Ugh, this whole project is getting harder every day! I suppose I could get more height in my fixtures if I put them on the outer corner of the shower but that would probably look pretty stupid.

 

[Terry]

You can't put a 2.5" hole in a 5.5" joist and expect it to hold anything.
The attic framing was meant to carry wall board. Not a living story. If you intend to create a living space there, you need to support it.

 

[ImOld]

I think you're missing Terry's point.

The attic area is not meant to be a habitable space.

I'm sure you have many building code violations already.

There are attics that are designed to become habitable spaces.

From the looks of it, yours is not one of them.

Does it stop people from attempting what you want to do?

Nope!

As long as no inspections are done, you'll get away with it.

That is until you try to sell the house.

Or the consequences of ignoring safe construction techniques comes home to roost.

 

[Jadnashua]

FWIW, 2x6 joists may not support a tiled shower or bathtub unless their span is VERY short (unlikely). General rules for holes in joists...never at the ends, never compromise the top or bottom, and limit the size of the hole. They get fairly specific, but those are the general rules. I do not see any vents in your rough layout, either.

 

[Johnfiorello]

Thanks for the concern about code. FYI we've had 2 different plumbers come in and look at the space and they both suggested drilling through the joist (both were from reputable companies) and we're fully permitted to do the work. If the attic wasn't meant to be habitable I'm sure one of the contractors we've had up there or the city who approved the project would have said something by now...

@jadnashua: How short? The joists are above the bathroom below, probably 7' from wall to wall. The rough layout didn't have the vent piping sitting there (the rough layout also was upside down and backwards (hence the p trap in the wrong direction...

Would it work to drill through if I sistered the joists? It's also possible I'll have 6' 8" if the shower head is in the last bay; do you think that's too close to the shower door to work? I haven't seen many people do that in my google searches...

We could avoid the fixture height issue if we put in a bath instead of a shower but I'm not sure what we'd want to do to reinforce the floor to hold the weight of a tile bath. I'm looking into that now.

JF

 

[Johnfiorello]

Just a quick update, I think we'll have enough height for the fixture if we run the drain pipe over the joists.

I ran a Deflectolator for supporting the shower and with 16oc joists at a 8' span that are 5.75"x2" the calculator said we were somewhere between L / 560 and 695. Since the max deflection for ceramic is 360 I think we'll be just fine. We could almost go with natural stone but we don't want to

But the next issue that comes up is: What do we do if the shower height is higher than the rest of the bathroom? Assuming we end up 6.5" higher than the floor, would we leave a step there? Would we want to raise the rest of the bathroom? I'd rather not because then that messes with the location of the toilet and is more $/work. I'm not sure about code for a step up into a shower, I'm looking into that now. I'm assuming you'd still have a curb for the shower so that could mean a 10" step up. Does anyone ever do something like that?

Thanks!

JF

 

[WJcandee]

If the attic wasn't meant to be habitable I'm sure one of the contractors we've had up there or the city who approved the project would have said something by now...

Contractors aren't engineers. Either are building inspectors, usually. True, they often know quite a bit about loads and such (as evidenced by the comments you collected here). However, if this thing was being built above my kid's bedroom, I would want to make damn sure he/she wasn't going to be killed by having a beautiful natural stone shower crush his skull while he slept.

Years ago, I had an excellent contractor install additional HVAC on the roofs of commercial structures in multiple jurisdictions. Every job was permitted, inspected and approved. Six months later, one shopping center owner had an engineering firm conduct a roof inspection (apparently required by a lender or insurer). Guess what? Our HVAC unit was dangerously-overloading the roof structure. A little snow, and it was likely to cave in. They gave me a simple-enough fix, albeit not a cheap one. Ultimately, additional stuff was welded in to the roof system pursuant to the engineer's fix. I then had them inspect other locations. If I recall correctly another one also needed some rework. Landlords were all grateful for the catch and were cooperative, as were the local authorities who appreciated that we stepped right up and fixed everything.

So it isn't always obvious to everyone involved that there's a potential issue, or maybe they don't have the skill set to truly ensure that there isn't an issue, or everyone assumes that someone else would have said something if there was an issue. Heck, the Citicorp Center in New York stood for years with a potentially-catastrophic engineering error, which was only discovered when some engineering students asked the engineer how he handled certain types of wind loads. His design hadn't, leading to a very-quiet months-long floor-by-floor project to weld additional bracing into the building structure.

Anyway, I personally think it's worth going out of my way to ensure a structurally-safe design when the alternative is to have something fall on my family's (or customers') head.

 

[Johnfiorello]

I agree @wjcandee, I do want it to be safe and you're right, just because they were plumbers doesn't mean they were right! I've been reading up on the load issue and while it seems we'll be good for the tile, it doesn't seem that there is a safe way to drill through the joists.

I'm going to look at the ceiling of the second floor again and see what would have to move if we ran the drain pipe below the joists. At the least, we'd have to cut open some cabinets but that may be our only choice now.

I'm open to any suggestions though!

JF

 

[Johnfiorello]

Ok, I think I have this figured out...

Here's what I'd end up with. There would be an 8" curb from the bathroom floor that you would step over to get in the shower. The shower would be 4" higher than the regular floor. I could make the curb higher if it needed to be...

How does an 8" curb and a shower that's 4" higher work? Since it's not a step it doesn't seem like it would be a tripping hazard and we'd have a shower door mounted on it... or should we make it taller than 8"?

 

[Jadnashua]

A tall step can be dangerous with wet feet. Someone can probably come up with the actual code about where and what size holes are acceptable in joists. Since a shower in the USA requires a 2" drain, and the hole should be at least a little larger so the pipe doesn't rub, I don't think it would be possible through a nominal 6" joist. As to whether sistering it would be sufficient, you'd have to talk with a structural engineer. It might be possible to reinforce it with steel, but again, a structural engineer would be required to run the numbers and give you a report, since without that, the general building specs would likely prohibit it. So, there may be a way, but also keep in mind, it may be close getting the trap in there without raising the pan slightly.

 

[Johnfiorello]

So, there may be a way, but also keep in mind, it may be close getting the trap in there without raising the pan slightly.

Thanks Jadnashua, that's what we ended up doing. We're raising the pan up enough to fit the trap with the proper slope. I think it's the best of both worlds. Now, we're not worrying about drilling through the joists and we'll have a little extra bracing for the pan.

Thanks for your input everyone. I'll try and post a pic once we put it together so you can see what we did.

Thanks!

JF

 

[Terry]

My sister's lake cabin has a tub that sets up high. When I've stepped out, I nearly break my neck.
I know going it that it's way up there, but after I shower, I forget how high it is.
My preference is a landing outside to step down onto that isn't so drastic.