Stacked Bathroom Question. Yes saving money by stacking but is it ok to be a little bit off?

[CaliSkier]

Hi,

So I am designing a 2 story addition to my house that will have a 1/2 bath down stairs, toilet and sink, and a full bath upstairs that will have shower - tub, toilet, sink, Looking at the two photos, you can see where the two bathroom layout, they are on top of each other and the top right corner is the same location as the top right corner of the bottom floor. The sinks on top are on the same wall as the sink and toilet on bottom. Can the toilet on top and the tub be ok to be on that side? Can't they just go through a few of the 2 x 12s (maybe 3-4) under the floor to get to the outside wall?

That is question 1.

Question 2: What if I moved the top floor over (as in down on the page about 8') and kept that bottom floor where it was. What complications does that cause me or can I just have it slope through 5-6 joitsts to the down pipe that would connect into the bottom floor?

2nd Floor ~7 x 7'

First Floor 4.5' x 4.5'

 

[Reach4]

Bathroom above bathroom should be OK. You will want the bottom bathroom stuff vented before its drainage joins something else. You will want to bring a dry vent down to the lower bathroom, and vent the lavatory. If your pipes are big enough, then that lavatory drainage can wet-vent the rest of the bathroom.

Oklahoma Plumbing Code 2015 based on the International Plumbing Code 2015 (IPC 2015)

UpCodes offers a consolidated resource of construction and building code grouped by jurisdiction

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OK uses IPC.

The most common way to vent a tub, shower, or toilet is to use a horizontal wet vent. A big example, which covers two bathrooms, is on the bottom of page 12 of https://www.iccsafe.org/wp-content/uploads/20-18927_GR_2021_Plumbing_Venting_Brochure.pdf

An important point is that horizontal wet venting only applies to bathrooms on the same floor, and that if you inject something else, such as a laundry standpipe or kitchen drainage, or drainage from a different floor, horizontal wet venting is done.

If you look at your project with this in mind, you will probably ease your plans.

 

[Sponsor]

 

[Tuttles Revenge]

The biggest obstacle to lining up bathrooms floor to floor is lining up the joists so that your larger toilet drain doesnt need to be drilled through joists and that the bottom floor plate either isn't sitting directly on top of a concrete footing or there are provisions to pass through it.

And as Reach4 alludes to, utilizing horizontal wet venting is a great way to eliminate a lot of venting work and fittings, but the top floor bathroom must connect to the drain downstream of the powder room fixtures if horizontal wet venting is used there.

 

[CaliSkier]

The biggest obstacle to lining up bathrooms floor to floor is lining up the joists so that your larger toilet drain doesnt need to be drilled through joists and that the bottom floor plate either isn't sitting directly on top of a concrete footing or there are provisions to pass through it.

And as Reach4 alludes to, utilizing horizontal wet venting is a great way to eliminate a lot of venting work and fittings, but the top floor bathroom must connect to the drain downstream of the powder room fixtures if horizontal wet venting is used there.

Thank you both for your help...

Can I do something like this? They are about 19 feet apart latterally and on different floors. Can I just go across like in the photo?

Top Floor Bathroom is on the left

Bottom Floor bathroom is on the right

Photo is an example of what I am thinking...Can I just go across the floor like in the photo?

 

[Tuttles Revenge]

Yes, plumbing often travels through framing members... However there are limits based on the diameter of the pipe and the size of the joists.