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Using Mollie bolts or other anchoring screws on thin plywood walls.

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  1. #1

    Using Mollie bolts or other anchoring screws on thin plywood walls.

    Hi,

    I have moved into an old walkup, and for some reason the concrete walls have been covered with most likely a plywood material. For insulation or perhaps easier routing of new electrical?

    In any case, I have been wanting to anchor furniture, such as a narrow Ikea wardrobe that may be prone to tipping over.

    The Ikea installation guys refused to install it against the wall saying it was a wood hollow wall. But my understanding is that wall anchors can do this job, and in fact doesn't IKEA themselves supply drywall anchors? Isn't plywood stronger than drywall?

    I will attempt to do this myself, but I wanted to see if you guys had experiences with this in hk.

    Thanks


  2. #2

    I should add I don't feel any studs, so I'm guessing these plywood panels are secured at the corner of the walls. Not sure what the regulations are or the contractor just did it ghetto syle


  3. #3

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    Plywood is actually formed from sheets of wood veneer and you can't consider it to have the normal strength of wood. Those sheets are bonded by an adhesive. Its strong enough depending on thickness to be used as a subfloor if properly fastened. But I'm not sure its prudent to use it in a vertical scenario when you don't know how it was fastened and how thick it is. I can see why the Ikea contractor refused. If the bookcase tipped over would be a serious liability. IMO, find the stud using a stud finder and drill though the plywood to secure that way if you really want to do this. At your own risk of course on how it works out. BTW I'm not a contractor.


  4. #4

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    Quote Originally Posted by SeptimusPrime:
    Hi,

    I have moved into an old walkup, and for some reason the concrete walls have been covered with most likely a plywood material. For insulation or perhaps easier routing of new electrical?

    In any case, I have been wanting to anchor furniture, such as a narrow Ikea wardrobe that may be prone to tipping over.

    The Ikea installation guys refused to install it against the wall saying it was a wood hollow wall. But my understanding is that wall anchors can do this job, and in fact doesn't IKEA themselves supply drywall anchors? Isn't plywood stronger than drywall?

    I will attempt to do this myself, but I wanted to see if you guys had experiences with this in hk.

    Thanks
    It sounds very wierd to have a hollow wall like that in HK. It is possible they've covered their concrete walls in ply to hide the state of the underlying concrete/plaster or to conceal pipework or wiring - Shoddy work no doubt.

    SO...... are you sure the wall is hollow? When you bang on it/press it hard is there any flex?

    If it doesn't flex but is definitely hollow then the plywood should be comfortably strong enough to attach a free standing wardrobe to. Naturally not strong enough to hang a wardrobe on, but just stop it tipping... yeah no probs. Better of course if you can find a stud (If there are any) and screw directly into that, though as HK flats are small the chances of any stud being in the right position is not great.

    So assuming it's 1/2" ply and hollow with a say a 1" or 2" gap you can use short wall anchors and normal short wood screws (double up though) so 4 fasteners along the top edge of the wardrobe.

    The problem you'll have though that if the ply has been placed to hide wiring/pipes it won't run in a predictable way and thus you'll need to use wiring/pipe detector. I have one and can do the job for you if you don't have access to one.

    For more strength you can use toggle bolts or molly bolts as you said (though I don't recall ever seeing molly's in HK) assuming that the cavity is deep enough.

    You could carefully (s.l.o.w.l.y) drill a small hole to test how thick the ply is and how deep the cavity is. For real strength you can drill straight through the ply then switch drill bits to masonry and put anchors into the concrete on long screws. You'd only need two that way.

    Over to you...Name:  Molly.jpg
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  5. #5

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    It sounds very wierd to have a hollow wall like that in HK. It is possible they've covered their concrete walls in ply to hide the state of the underlying concrete/plaster or to conceal pipework or wiring - Shoddy work no doubt.
    Some commercial / industrial spaces have been known to be converted to residential using drywall type structures.

    I know one building close to LKF which was commercial - got converted to residential by the joint owners and then drywalled. Also done in a crap load of industrial places in locations like Wong Chuk Hang.
    Sage likes this.

  6. #6

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    Quote Originally Posted by shri:
    Some commercial / industrial spaces have been known to be converted to residential using drywall type structures.

    I know one building close to LKF which was commercial - got converted to residential by the joint owners and then drywalled. Also done in a crap load of industrial places in locations like Wong Chuk Hang.
    Well I guess you get some noise insulation (with a cavity) if the building was industrial.... But 'a walk-up' doesn't sound like that.

    If it is drywall and hollow it may well only be 9-12mm - I'd be more inclined in that case to drill through into the concrete with longer screws and wall plugs.

  7. #7

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    You can follow this method - very straight forward.

    But:
    1) Wires!
    2) Don't countersink the screw heads whether ply or gypsum/plasterboard/drywall [all the same thing]
    3) Don't over-tighten the screws, you could easily rip through the drywall/ply.

    https://www.youtube.com/watch?v=0oEeYKnfsts

    Last edited by Sage; 14-10-2020 at 12:10 PM.

  8. #8

    Thanks for the replies.

    Yes the wall is hollow since knocking on it is like banging on a drum. And pushing it you get flex which makes me think the studs are super wide, and the wood is thin. The walls do provide crazy sound insulation which isn't normal in these flats.

    As for drilling to masonry, this wall in particular is a fake wall, which begs the question how is it being supported; there must be some frame.

    I have a electronic stud finder, but I'm not getting consistent readings. Might do tiny pilot holes.

    I am not really a handy man, but I want to think I can at least prevent a wardrobe from tipping over. So I'm not looking for the wall to withstand a lot of vertical load.


  9. #9

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    If you are not too concerned about damage, can you anchor the top of the unit to the ceiling with a cable type arrangement?