Looking for advice on finishing roughed in full bath

[JakeOz]

Hello,
I've recently joined this forum in hopes of getting some advice from more experienced people as I attempt to start finishing a full basement bathroom that was roughed-in during construction. We bought the house several years ago and I am now ready to tackle the project. I am fairly experienced in DIY and home renovation and have a good selection of tools available. I will be applying for permits soon but want to have a better idea of the path I am going to take while building out this space.

There were no plans or drawings left by the previous owner so I am only going by what I see currently in the space. The basement is mostly finished already except for this space adjacent to the stairs. When you turn the corner from the stairs there are two doors, which both enter an open unfinished space. One the one side is the rough-in for a full bath, with plumbing already in the concrete floor, and on the other side is an open storage space. There is currently no wall between the doors/spaces. Near the center of the open space is a soil stack from the upstairs powder room and on that wall against the stairs is a vent pipe for the toilet (I think) and a sanitary tee where a utility sink has been connected previously. Attached are some pictures and below some of my initial questions, thanks in advance for any advice you can provide :O)

1. I believe the intent with this space was to frame a wall between the doors to separate the spaces. Can I build this wall to enclose the soil stack, say with 2x6 or 2x8 framing, or should I go on either side of it? Or possibly leave a bump out in the wall at that location? See the red lines for proposed wall.

2. The black cover on the floor for the shower/tub drain is pretty much in line with the stack and where the straight wall would be. Should I plan on moving this drain location in the slab or build the wall around that area for a "nook" shower. I was planning to do a tub/shower combo install.

3. Is the currently installed utility sink plumbed appropriately? I would like to have a proper vanity and sink here for the finished bathroom and move the utility sink to the other side of the wall once built so that the utility sink is in the storage side of the partition.

4. If I move the utility sink to the other side of the wall, would I be able to connect it to the main soil stack somehow for the drain? And could I tie into the vent line for the upstairs bathroom to properly vent it? I would really like to have the sink available on the other side of the proposed wall for future use.

5. Is there any way that I would be able to include a french drain in the floor on the storage side of the partition? Can that just tie into the main soil stack if I break up the slab to install it?

Hopefully my questions are clear enough for you to provide some helpful feedback. I can provide addition photos or details if that would help. Thank you again for taking a look at this, I greatly appreciate it!

Cheers,
Jake

 

[James Henry]

That vertical drain that is behind the toilet and run to your laundry sink could be the wet vent for the toilet, if that's the case, you can't put a lav and a laundry sink back to back on a wet vent system. You can't just guess where the drains are under the concrete you have to get them professionally located if you want to do it right and not have problems down the road, then you can sketch the layout of the drains under the concrete and design your floor plan from there.

 

[Sponsor]

 

[JakeOz]

That vertical drain that is behind the toilet and run to your laundry sink could be the wet vent for the toilet, if that's the case, you can't put a lav and a laundry sink back to back on a wet vent system. You can't just guess where the drains are under the concrete you have to get them professionally located if you want to do it right and not have problems down the road, then you can sketch the layout of the drains under the concrete and design your floor plan from there.

Thanks for the reply James. I do believe that the vertical drain behind the toilet is a wet vent and I don't really have much guidance on how things were laid out under the slab as the previous owner did not give me any information aside from saying that he added that laundry sink to the sanitary tee that was already present on the vertical vent line (and pointing in that direction). He cut off the cap and added the ~3ft run to the sink location. That makes me think that the intent was for a sink to go there in the finished bathroom, but you are saying that is not allowable? I've attached the only documentation that I have for the space, a hand drawn sketch likely from one of the contractors that originally finished most of this basement. It shows the shower on the back wall, toilet where expected based on the floor flange, and i think a sink opposite the toilet by the soil stack in the floor? They also show the wall built where I expected it to be, between the two doors into this space, albeit not enclosing the soil stack. Would it even be possible to put the sink opposite the toilet draining into the stack and tied into the vent line in the ceiling? I guess it would probably be best for me to find a plumbing professional to come investigate things and give me some in-person guidance?

 

[James Henry]

Only a lavatory can be connected to that vertical drain, nothing else, if that is the wet vent for the toilet.