MDF & Plastering

Discussion in 'Carpenters' Talk' started by Taz9, Oct 9, 2021.

  1. Taz9

    Taz9 Member

    Hi guys

    I'm in the process of building some drawers which will fit inside a recess (previously it was a couple of shelves).

    The drawers have an mdf carcass and the wall around the recess will be plasterboarded and plastered.

    I want the mdf carcass to be flush with the finished plaster and wondered if there's a product/idea which will create a 'divide' between the plaster and the mdf as obviously without such a solution, the mdf will soak up the plaster.

    I appreciate that I could have it plastered first and then slide the carcass in but presumably the plaster coat would end up being very thin around the recess opening (approx. 1m x 0.5m) and more worryingly, it would make life difficult if it was uneven as the carcass wouldn't be flush with the wall on all 4 sides.

    Thank you in advance for any tips/ideas.
     
  2. CGN

    CGN Screwfix Select

    you’ll end up with a hairline crack regardless of approach. You could bead up to the sides of the drawers using either a stop bead, or just a standard thin coat angle bead, or use some sort of trim over the join .
     
    tore81 likes this.
  3. Taz9

    Taz9 Member

    Thanks for the reply. I didn't even think of there potentially being a crack.

    Would a stop bead create a good enough barrier between the plaster and mdf?

    The trim idea crossed my mind but then I'd lose the flush look
     
  4. Wayners

    Wayners Screwfix Select

    Duck tape on side of mdf stops the moisture.
    Masking tape then duck tape over if protecting and want to remove or you won't get it off. Really need a cover strip bridging two surfaces to stop the crack as temperature change will cause a crack.
    You can fill between mdf and plaster with polymer mastic and fingers crossed it holds/gives. 0B1 or CT1 type mastic in white
     
    Taz9 likes this.
  5. CGN

    CGN Screwfix Select

    yes, as you can set it to fractionally overhang the plaster board. You’ll have to be extremely precise though. Another option would be to set your drawers flush with the plasterboard and just lip the stop bead over on to the mdf. Yes, you’d loose that totally flush look, but it would probably look better in the end.
     
    Taz9 likes this.
  6. tore81

    tore81 Screwfix Select

    Maybe infill pieces look nice then scribed in tight
     
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  7. Mr Rusty

    Mr Rusty Screwfix Select

    to stop the crack I've had success with machining the edge of 15mm MDF to make a rebate, scrim taping from PB into the rebate and then skimming up flush to the higher part of the MDF.
     
  8. Taz9

    Taz9 Member

    This sounds like a plan - how did you stop the mdf soaking up the wet plaster please?
     
  9. Mr Rusty

    Mr Rusty Screwfix Select

    it didn't. i did nothing at all.
     
    Taz9 likes this.

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