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Thread: Adding a bathroom on a slab

  1. #1

    Default Adding a bathroom on a slab

    Hello,

    I am thinking about converting my garage into a media room and adding a bathroom. I would like to put in a shower stall, toilet and sink. My garage is on a concrete slab.

    I have a long closet in my garage that houses my hot water heater. On the other side of the wall from my hot water heater is my clothes washer. I would like to turn the rest of the closet into the bathroom.

    I am looking for ideas on how to easily add the desired bathroom features. I have no idea where the drain line runs through the slab and I doubt it is in the room I want to turn into a bathroom.

    Like I said, I do have the hot water heater in the closet and on the other side of the wall the washer. I don't want to elevate the entire floor of the bathroom.

    Your suggestions would be greatly appreciated.

    Swag

  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
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    A few fundamentals...the drain lines must slope 1/4" per foot. You need to find out where your sewer line is. If the slope from that area to the existing line is not the right pitch, you can still do this, but you need to add a pump and a basin. Gravity is always better if you can do it. The toilet needs a minimum of 3" line, a shower 2", and normally, anything under the slab needs to be at least 2" - but a vanity only needs 1.5". You don't want to make many turns in the drain line, and may want to join the sewer somewhere outside rather than tearing up the slab in the house to attach.

    A garage is often on a sloped floor, so depending on what you want, there are ways to level that up that aren't a big deal, but you may not need to do it, just be aware of it - shims on things may be required.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  3. #3
    DIY scratch-pad engineer leejosepho's Avatar
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    Nov 2006
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    After you know where your main sewage line exits the perimeter of the house, the next question is about how far your desired bathroom is from the perimeter also, and then how far that possible exit point is from the sewer line. Ideally, the closet you want to convert is along an outside wall and not far from the sewer line, but it does not sound like that is what you have. In any case, a trench (with branches?) for a drain line would have to be cut in your floor, and that line would have to exit the perimeter of the house and connect to the main sewer line. Also, you will need some venting, and that *might* be able to be connected to the vent for your washer line on the other side of the wall. With the water heater already in the area of the proposed bath, water line connections should not be difficult.

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