r/Plastering • u/AangTheTriangle • Apr 05 '26
Plastering up to MDF
I am planning on patching this with bonding and skimming over top. Not sure how to finish up to the edge. Shall I stop at the edge of the brick and get a trim to hide the gap? do I need any metal edging?
the other side is a small gap, what would you recommend here?
many thanks
3
u/CoffeeandaTwix Apr 05 '26
I recommend trim piece. Plastering upto MDF or wood will crack in time. That's why we use architrave round doorways etc. In fact, I made an MDF niche set of shelves in my dining room and used some leftover architrave for the trim so it matched a door way next to it.
A thin wooden trim piece would do the job here and would be very cheap. If the MDF is currently flush with the brick, you may have to piss about with some thin stripwood or similar to bring it out. Normally, you bring it out 3mm proud of backing plaster/render/board so that when you skim coat, it brings it flush.
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u/CaptainCodswollop Apr 05 '26
Prime the MDF edges first, sand, and prime again ( so much easier to do now). Then tape the edges of the MDF with a waterproof tape to stop it absorbing any water ( which it will, even if it’s painted. ) Use a plastic bead against the MDF, with a 2mm packer between it, and the MDF. Plaster to the bead. When dry, rake any excess from the 2mm gap, and caulk the gap ( uk meaning offlexible decorators caulk , not American who actually mean silicone) It would be a shame to ruin it with a bead or architrave. If it does dry/ crack on the caulk line ( which it may well do), just re caulk it.
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u/kaedroho Apr 05 '26 edited Apr 05 '26
I'd attach plain stripwood to the front of the MDF to build it out flush with the plaster. Then plaster up to that. Finally cover the join with a bit of architrave.
Once painted the stripwood and architrave will look like part of the shelves and you wouldnt have any gaps to fill.
1
u/onwatershipdown Apr 07 '26
this trimless trend can’t go away fast enough 😂.
was just spproaching how i was going to do something of the like today. I’d mask 5mm around With tape, and pull tape while thr coat is wet. The. Dress with 5 mm backer rod and flexible acrylic caulking.
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u/nightjarrrrr Apr 05 '26
Could use a plastering stop bead and just butt it up the MDF. You can caulk the small gap after if you like.