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Thread: Hit a brick wall...could really use some advice

  1. #1
    Scientist jeremytl's Avatar
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    Default Hit a brick wall...could really use some advice

    Actually, I hit a slab. I'll start from the beginning.
    We're putting a half-bath in a small 3 bedroom/ one bath house built in '63.
    Where the new half-bath is going: it's an area that at one time used to be a patio adjacent to a carport. 20 or so years ago, this area was transformed into a bedroom and adjacent laundry room. So we tore out a wall of the bedroom to join the laundry room and make it big enough to accommodate a pedestal sink and toilet. Everything was fine until we pulled a piece of the floor up to take a look. There is a concrete slab. We drilled through it with a 1/4" bit just to see how thick it was and what was underneath. It's about 6" thick with about a foot and half crawlspace underneath. The big mystery is why they used a rebar mat to pour a slab onto, when they could have used wood floor joists to accomplish the same thing.. But that's another....
    So I need a core drill right? I mean I have to get through it to plumb the toilet and sink. Here is a pic. In the pic you can see the hot and cold for the washer, the drain and the vent, which we were planning to tie into and go to septic. I'm open to any other suggestions.

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  2. #2
    DIY Senior Member dlarrivee's Avatar
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    Default

    Rebar mat?

    Is this a suspended slab, or not?

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    Scientist jeremytl's Avatar
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    I don't know if I can accurately answer that. With my limited knowledge. I didn't know there was such a thing as a suspended slab. It appears that the perimeter of the slab is supported with block foundation. Additionally, there are at least two block/brick pillars supporting the center of the slab. But it also appears that there was a rebar mat that the concrete was poured into. It sags in some areas. In other words, the slab may be 10" thick in areas where the mat sagged the most. Other areas, the slab may only be 4 or 5" thick.

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    DIY Senior Member dlarrivee's Avatar
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    This could be a can of worms, any more pictures?

    Looks like a decent amount of black mold on that paper faced drywall too?

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    Scientist jeremytl's Avatar
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    Default

    that black is old tar paper or some similar moisture barrier paper.that used to be an outside wall.
    so, i'm looking for comments on plumbing through the slab or any alternative ideas.

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    Moderator & Master Plumber hj's Avatar
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    I hope you realize that the drain for the sink is NOT big enough for a toilet, so you will have to find a larger pipe, somewhere, and run your drain line to it. They COULDN'T have "poured the mat" without a form underneath it to support the concrete when it was poured, so your analysis is faulty. The ground may have settled underneath it, but 18" is too much for that to have happened, although I did see a grocery store one time where the settlement was even greater than that.
    Last edited by hj; 04-03-2012 at 08:03 AM.
    Licensed residential and commercial plumber

  7. #7
    Scientist jeremytl's Avatar
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    Default updated w/ PICS... couple more questions

    Plumbing through the slab is no longer an issue, it is all figured out. I have a couple more questions though. First, here are some updated pics:

    pic of suspended slab poured on rebar mat (i think)
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    future location of fixtures
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    Scientist jeremytl's Avatar
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    I wasn't ready to post that. here is one more pic:

    in this pic you can see the hot and cold lines run up through the slab (tee'd off from the hot and cold supply to the washer underneath). i will tee off the cold and run through the future wall for the toilet supply
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    my question is regarding the flooring and drain line from toilet. should i go ahead and install the flooring before i set the toilet? i am going to install pergo to match the adjacent room pergo. i just don't know how to set the flange. on top of osb or pergo?
    next, i plan on tying in the 3" toilet drain line to the 3" EXISTING sink drain line to the other bathroom (not shown) which is 3" cast iron from 1960's. then use the drain line from washing machine to tie the 2" sink drain line to. and there is a vent there for the washing machine already which i will tie into. all good?

  9. #9
    Retired Defense Industry Engineer jadnashua's Avatar
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    Floating floors are a conundrum - it normally shouldn't be anchored...normally, a flange is screwed through the finished floor, into the subflooring or slab so that the flange sits on top of the finished floor. You'd have to read the instructions for the Pergo to see what they want or give the a call. BTW, a much preferred flange is one with a metal SS ring, not an all plastic one. Those with the metal ring tend to be much stronger.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  10. #10
    Moderator & Master Plumber hj's Avatar
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    Flange on TOP of whatever the finished flooring is. DO NOT install the toilet then cut the flooring around it, unless you want to redo the floor when you have to change the toilet and the opening does not fit the new one.
    Licensed residential and commercial plumber

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