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Thread: How to prep a laundry room floor with floor drain for tiling?

  1. #1
    DIY Member benze's Avatar
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    Default How to prep a laundry room floor with floor drain for tiling?

    Hi,

    I'm in the midst of renos of my basement, and am adding a 5' x 7' laundry room to the space. My current floor is the concrete slab, but I am planning on putting down in 1" rigid insulation, covered by 3/4" plywood. I haven't done the walls yet, but am planning on using regular 1/2" drywall.

    I'm a bit stuck at this point as to figure out how to plan for the floor properly. I have roughed in a 3" floor drain in the space just in case there is any leaking, overspray, etc, but am not quite sure how to prep the floor appropriately. I'm a little confused / perplexed how to best slope the floor towards the floor drain, and whether or not I need to use something like Ditra or some other membrane to waterproof the floor.

    How much slope does the floor need to direct water to the drain? How does one acheive this slope? Do I need a waterproof membrane like you would in a shower? Afterall, it isn't really a "wet" space, like a shower which is designed to be soaking wet all the time, but rather just a drain to catch any spillage or accidental flooding that may occur.


    Thanks for any advice / pointers / suggestions / etc...

    Eric

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    Moderator & Master Plumber hj's Avatar
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    I will be almost impossible to "slope" a plywood floor, unless you do a lot of "piecing together". And, sealing a drain to a wood floor is also a very difficult task.

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    DIY Member benze's Avatar
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    Agreed. I have no visions of being able to slope the plywood. Does that mean I have to make a mortar bed on top of the plywood, following the same 1/8 to 1/4" slope per foot as in a DWV line? And then put a waterproof membrane? Or is all that overkill for a laundry room?

    Thanks,

    Eric

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    Moderator & Master Plumber hj's Avatar
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    Qverkill, and IF you were going to do it, I would leave out the plywood and place the mortar bed on the concrete. The waterproof membrane would then go UNDER the mortar bed and be attached to the floor drain's flashing collar. That would simplify the entire operation.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    If you treated it as a shower floor, you could use Ditra, with a band of Kerdi around the Kerdi shower drain. Or kerdi the whole thing with maybe Kerdi band at the walls. You'd still have the problem of it potentially running out the doorway. Getting cabinets, the machines, and say an ironing board to sit level without rocking will be more of a challenge. You could use a paint on waterproofing under the tile like RedGard. The harder thing is waterproofing to the drain so you don't get an accumulation of moisture underneath if something catastrophic occurs. But, with some slope and a working drain, the vast majority of any moisture would just go down the drain, so heroic efforts may not be called for.
    Jim DeBruycker
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    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Senior Member chefwong's Avatar
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    This may be a dumb question but for you plumbers out there, would you recommend a floor drain in the basement....
    Assuming all things are gutted and the user has provisioned a laundry drain pipe stub and or laundry sink ?

    Water will eventually evaporate in whatever drain he is considering unless it's topped off ?

    Just curious as I too have wondered the benefits or cons of having a floor drain.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    You could tap off the drain pipe for the washing machine, so when it drained, it dumped a little down the drain. A trap primer is a good idea unless you regularly do something like mop the floor and use it to dump some of the water.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  8. #8
    DIY Member benze's Avatar
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    Quote Originally Posted by jadnashua View Post
    You could tap off the drain pipe for the washing machine, so when it drained, it dumped a little down the drain. A trap primer is a good idea unless you regularly do something like mop the floor and use it to dump some of the water.
    I was suggested to use a 3" floor drain and use mineral oil to fill the ptrap. Even if using water, the ptrap would take a significant amount of time to evaporate. Or, use a primer, as previously suggested.

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    DIY Member benze's Avatar
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    Quote Originally Posted by jadnashua View Post
    If you treated it as a shower floor, you could use Ditra, with a band of Kerdi around the Kerdi shower drain. Or kerdi the whole thing with maybe Kerdi band at the walls. You'd still have the problem of it potentially running out the doorway. Getting cabinets, the machines, and say an ironing board to sit level without rocking will be more of a challenge. You could use a paint on waterproofing under the tile like RedGard. The harder thing is waterproofing to the drain so you don't get an accumulation of moisture underneath if something catastrophic occurs. But, with some slope and a working drain, the vast majority of any moisture would just go down the drain, so heroic efforts may not be called for.
    Agreed about the rocking / etc, which is why I can't help but wonder if sloping it like a shower floor is way overkill. Esp considering that it isn't really going to be used often (if ever). Which is why I am leaning towards leveling the floor and leaving the floor drain. If ever there is a leak or water seepage, then just squeegee it down the drain. However, then the next question becomes if I still need a waterproof membrane under the tile and up 6 inches on the walls. Then just use a small threshold to prevent anything from spilling out the room. I don't know if I could try to slightly slope the tiles using the thinset, but am afraid that will be a recipe for disaster if I attempt something like that.

    Thoughts?

    Thanks,

    Eric

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    Retired Defense Industry Engineer jadnashua's Avatar
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    To avoid compound slopes (like in a typical shower), you could move the drain to one end, and use a trench drain. Then, the floor would be flat, but one simple sloped plane.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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