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soropa 03-18-2012 05:08 PM

Attic bathroom
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I have a house that is a hundred years old, has a basement, ground floor, and unfinished attic. I am in the process of converting the attic into liveable space and want to add a bathroom. Currently the house has one bathroom on the ground floor. The main drain is of 4" cast iron and runs horizontal with a gradual decline in the basement. The toilet, lav, and tub drain into the main drain, as well as the kitchen sink, and laundry.Where the toilet attaches to the main drain, from that point the cast iron runs vertically through the house and vents above the roof.
I would like to tie-in to the current 4" cast iron vent upstairs. I have upload a pic to illustrate what I'm talking about. The majority of the pic shows what my current set-up is, the part that is drawn in blue is my proposed set-up. Will this work? What I guess I'm most worried about is venting. I keep reading conflicting reports about venting, wet-venting etc, and what is necessary. I also would like to know if there is a particular order to the drain that is required. For example currenlty I have the new bath lav drain attaching to the new toilet drain and the new tub drain attaching to the new lav drain. Could that be reversed? For example could the new tub attach to the new toilet, and the new lav attach to the new bath instead?
Also you will notice on my proposed set-up in blue that I added an individual vent line for both the new lav and new tub that attach to the main vent at a higher point. Is this necessary? I only added it because I keep seeing plumbing diagrams where each fixture i.e. lav, tub, etc each have an individual vent line that attaches to the main vent. I'm confused as to why this is neccessary as my current set-up does not do this. If you notice my current lav, tub, kitchen sink, laundry just have drains that attach to the main 4" cast iron, and no seperate vents. As I said the house is 100 years old, but for the 10 years I have been here haven't had any problems with plumbing drainage/ or odors. Thanks for any and all help!

TheEplumber 03-18-2012 05:23 PM

199 Attachment(s)
Plumbers such as myself go to school for a min. 4 yrs. to learn code. I can't explain it all in a forum. What I will say is that what you have drawn will not work under the UPC. You cannot wet vent multiple floors. If that project was mine, I'd bring a 3 or 4" waste stack up to the top floor and vent those fixtures on that stack.

MassDIY 05-03-2012 07:25 PM

Update, please.
I am contemplating doing the same to my attic and have tried to research on how to do it. Did you do this project? If you did, did you go with your drawing or did something else?

I have been looking for videos and posts on how to add an attic bathroom but it's like looking for Bigfoot!!


Alan 05-03-2012 09:06 PM

Your first problem is converting it to a living space.

See here :

Note the point in the video where he says "You cannot convert an attic into a living space"

MassDIY 05-03-2012 11:17 PM

Thanks... ?
What is the definition of "living space"?
I have many friends who own houses where the attic is a "living space".

joecaption 05-03-2012 11:27 PM

Before going to far with this plan make sure the floor joist will even support living space.
Any old house I've ever worked on had sagging ceiling from the joist not being strong enought to support plaster.

Alan 05-04-2012 09:20 AM


Originally Posted by MassDIY (Post 914057)
What is the definition of "living space"?
I have many friends who own houses where the attic is a "living space".

And those houses were either originally designed for the attic to support the load, or they were added onto later either properly or improperly.

You're looking at a pretty extensive project to convert an attic into a living space as you can see from the video.

Do you have pictures of the current state of your attic?

MassDIY 05-04-2012 09:28 AM

Attic remodel
My apologies. Unlike the original post, my house is not old. Built in 2004, the attic has I-joist and, as I understand, can support the weight.

MassDIY 05-04-2012 09:29 AM

I will supply pictures as soon as possible.

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