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Thread: Need opinion on mounting bathroom sink

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  1. #1
    DIY Junior Member Dan W.'s Avatar
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    Default Need opinion on mounting bathroom sink

    Hi! This is my first post here. I've spent a lot of time at johnbridge for tile work, and I see that site mentioned here often, so I'm sure this is a good resource as well. Here's my issue:

    I'm redoing a half bath and need to mount a massive porcelain sink to the wall. The sink was made by Pegasus and is 36" wide by 22" deep. There are two porcelain legs for the sink to rest on, while the back of the sink lowers down onto a metal bracket that is screwed into the wall. The instructions appear to be translated into English from Chinese, so you know how that goes. They recommend that you mount a 2x4 between the studs and screw into that, or even lag screw with toggle bolts through the 2x4. My wall is configured a little differently, as shown in the attached photo. I've got cinderblock with 3/4" furring strips. The area in the photo is now sheetrocked so whatever I do I'll have to cut out a hole. So the question is what is sufficiently strong to hold this sink, which weighs about 75 lbs? Here's what I was considering to do: Nail a 1x4 or 1x5 to the cinderblock with those flat cinderblock nails (I used about two boxes of 'em in the adjoining room). Put the sheetrock back and drill through the sheetrock, 1x5 and through the cinderblock. Tile the wall, leaving a gap for the 4 holes in the metal bracket. Then, I'd mount the bracket with 4 toggle bolts going through tile, sheetrock, wood and cinderblock. It seems to me this would be enough, but is there a better way to do it?

    A related question: I need to move the sink about a foot to the left of where the existing drain is. The other side of the wall is open to the basement, so I was going to cut the copper pipe and punch a new hole to the left for a new drain in PVC. However, I want to leave the hot and cold lines where they are (long story short, it'll be a real pain to move them). The sink is massive so I don't think you'll really see that the hot/cold lines are not centered around the drain. For reference, in the photo there is a hole in the cinderblock about a foot to the left of the drain, and about a foot higher. I'll be mounting the bracket against the cinderblock above this hole. So the new drain line will be at the same height as the existing one and directly under the bracket.

    Thanks for any comments!
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  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
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    Drill a hole big enough to then put a stack of washers over the shaft of the toggle bolt so you can fill the space between the cinderblock and the ouside of the drywall. then, when you tighten it down, you won't be trying to compress the drywall, and will be tightening it up on the washers. If you had some pipe, you could cut it and use it as a spacer as well. Or even a holesaw, and use wood. If the wall isn't straight, or the sink isn't flat, don't try to tighten it too much, or you'll crack the porcelain.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  3. #3
    DIY Junior Member Dan W.'s Avatar
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    Washers! Beautiful... so much easier. One point of clarification, though. The back end of the toggle is obviously going to spring out and latch against the back of the cinderblock. The front end of the toggle bolt is going through a metal bracket, which is a plate about 6" long and 3" high. So the toggle is securing this plate to the wall, and the porcelain sink then slips over the plate to bear its weight. So the weight is really being held by the cinderblock alone. I guess the washers will provide some stiffness behind the wall so that I'm not trying to collapse the tiled wall when I tighten the plate.

    Just trying to figure out exactly what is holding the weight.

  4. #4
    Retired Defense Industry Engineer jadnashua's Avatar
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    Think of the washers as an extension of the cinderblock wall so it is now flush with the drywall. WHen you tighten things down, the bracket will be tight to the cinderblock, and if you get your spacer the proper depth, up against the drywall (but applying no pressure). The bracket will be as strong as if it was attached directly to the cinderblocks. So, if I understand what you have, the bracket would be attached by the toggle bolts to the cinderblock wall, then you hang the sink on the bracket. You can use whatever you want for the spacers to fill that depth as long as it won't compress - this is what allows you to get it tight.
    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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    Moderator & Master Plumber hj's Avatar
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    The weight is a "shear" weight, actually, NOTHING is supporting the sink other than the downward force on the toggle bolts, and the strength of the bolt itself. Therefore, you can just use toggle bolts which hold the plate to the drywall, and unless the toggle bolt is "sheared off" it will hold the sink.

  6. #6
    DIY Junior Member Dan W.'s Avatar
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    It makes sense that the bracket installation is only as strong as the toggle bolts. However, it would seem to me that if you put something solid like washers or a 2x4 behind the bracket, it gives something strong for the bracket to tighten up against. If nothing solid were there other than tiled sheetrock, I might be able to over tighten the bracket and deform the wall and/or crack the tile. With the washers or pipe at the correct thickness, you aren't putting any stress at all on the wall.

    I have to add that this might be a moot point. We are looking at the sink and are starting to think it is just too big for this small bathroom. We got the sink for 80% off about a year ago, and will rarely use this bathroom. Even so, I'm not sure that is a good enough reason to use something that is really too big. Anyway, whatever sink we do use may have this same problem, so it's not a wasted discussion.

    Thanks again!

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