Drypack/deck mud subfloor for Forbo Marmoleum Click - sounds hollow, failure?

Discussion in 'Floor Preparation' started by KKohler, Dec 17, 2017.

  1. KKohler

    KKohler New Member

    Hi guys!
    I originally posted this on John Bridge but Kman over there suggested also coming over here because y'all will know more about our chosen finish floor, Forbo Marmoleum Click.

    Here's the story - We are half DIYing/half-contracting a gut remodel of the 110 sq ft kitchen in our 1950 Levitt style ranch. The house has a slab on grade with original hydronic radiant heat floors, and is covered with VAT throughout. The slab had sunk down from the footings about 1" over the last ~70 years, and in order to install new flooring or cabinets or basically have anything along the walls, a new subfloor was needed. We did quite a bit of research on using self-leveler ourselves, but in the end it felt like biting off more than we could chew and ended up deciding to hire a pro. Alas, it's looking like that hasn't worked out so well either.

    The pro we hired recommended drypack over self-leveler since we had an inch of depth to cover, and his rationale and the bit of research we did on John Bridge indicated that made sense. When the drypack was installed the original VAT was removed prior to installation and all of the mastic from those had either dried up or sunk into the slab from the radiant heat. The drypack was put down with a sprinkling of Portland cement under it to bond it, but no wire mesh was used. When the slab was installed our radiant was still off, we turned it on about 3 wks later. The contractor knew about it and when asked couldn't offer any advice as to how long to wait to turn it on.

    About 3 weeks later (after we turned on the radiant - coincidence?), while we were still waiting for our finish floors to arrive, we noticed a 2'x3' area that sounded very hollow. We called the contractor, he came out and banged on it, did a lot of cussing under his breath at the worker that performed the job and said he'd rip it out and fix it. It came up super easy, and several days later he came back, prepped the area with a primer and poured self-leveler. He apparently tried to stuff newspaper into the original foundation/footing crack to stop the self-leveler, which clearly didn't work, so now that corner of the room doesn't sound hollow but it's no longer flat enough for flooring to go on top without another fix.

    To make matters worse the hollow sound had spread from that area (and continues to spread) and now about 2/3 of the room sounds that way, and there are cracks that also seem to be getting worse. When we told the contractor, his response was: "The hollow spots could be coming from the floor underneath. I spoke to several contractors and they said it's very common in Levitt houses. I assure you that the concrete slab isn't going anywhere unless it continues to settle which a possibility."

    This sounds like BS to me, given that a) He already thought it was enough of an issue to fix it in one area and b) the area he fixed feels and sounds solid as a rock now, so it doesn't seem like an issue with the slab itself or bonding something to it if done correctly?

    So we had 2 other contractors out to look (a family friend who was in town for the holiday) and a local guy who we'll probably hire to fix it, and both looked at our marmoleum click tiles and said it *might* be find for a while, but if it was their house, they'd tear up the subfloor and start over.

    Sorry for the novel! Given that this is a kitchen and having to take out everything to fix a subfloor later could be a nightmare, we want to make sure we're doing the right thing. We're leaning on the side of having it ripped up and redone with a primer and self-leveler as those two guys both recommended.

    My question to anyone familiar with marmoleum click is, does that sound like the way to go? And how bad does this make the first guy look? Should I be fighting to get my money back or is it "good enough"? (And I mean, hey, if that's the case that'd be great to hear, I'd love to not lose the money and get to spend the holidays fixing the mess in the corner and installing my floors.) Is there any special underlayment we should be using in this situation? :DThanks in advance for any advice and help!

    The first two pics are the area with the fix and the large crack that has kept spreading and sounding more and more hollow. There are other cracks/hollow-sounding areas throughout the room pictured as well.
    20171214_204013.jpg 20171214_204144.jpg 20171214_214555.jpg 20171214_214727.jpg
    Last edited by a moderator: Dec 17, 2017
  2. Jim McClain

    Jim McClain Owner/Founder Administrator

    Is that really dry pack, or is it a mud bed? Neither is suitable for prepping for Marmoleum, as far as I know. Dry pack is designed for deep cracks, not whole areas of flooring. What is dry pack? - Concrete Construction Magazine

    There are a number of ways the floor could have been prepared for your new flooring. What is the chance that what has been done so far will be removed to do the job right?
  3. Mike Antonetti

    Mike Antonetti I Support TFP Senior Member

    Several issues an experienced Floor preparation technician would take note of. First- cutback is a bondbreaker for the Portland neat cement to bond to. 2- Portland takes time to cure, was it bagged deck mud or mixed with Portland and sand. 1”? I’m not comfortable with that thickness, only if necessary(shower drains) 3. Was proper curing of mud bed done? Misting/cover with visqueen?

    Perimeter expansion joint? Usually 1/4” roll foam either premade or sill foam. If the heat expanded the mud it would have space needed to expand instead of being forced upward cause there’s no where else to go!

    Proper primer for cutback residue? Mapei uses primer T, I think instead of L for residue,what brand was used in your application? I’d be Leary on Relying on primer but a concrete surface profile of 3-5 I’d sleep nicely.

    I talk to my shower floor and say how I hate the hollow sound from water drips. I dropped a spoon today and noticed the corner tile in my house is hollow, why do I search for hollow and then dislike hearing it?
  4. KKohler

    KKohler New Member

    Thanks for the input! I believe it is a mud bed, although the contractor that installed kept referring to it as dry pack.

    We've decided to definitely to have it pulled up and redone, so any tips on what *should* be used instead is much appreciated!
  5. Barry Carlton

    Barry Carlton I Support TFP Senior Member Published

    You do realize that the Marmo click will have a hollow sound as well right??
  6. KKohler

    KKohler New Member

    Hi Barry, it's not the sound itself that bothers us, it's the worry that over time the hollow areas of the subfloor (that are already cracking) will continue to shift and settle and that those issues will telegraph up through the finish floor.

    I've been told by 2 contractors who looked at the mud bed and the Marmo tiles in person that it *might* not cause issues with the Marmo, but they weren't personally familiar with the product.
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