Gaps in Plaster Board

by Tony
(Barrow in Furness)

Paul. In preparing for skimming a wall,I have fit plaster boards. This has resulted in gaps of varying depth (up to about 7mm in places between the top of the boards and the ceiling. " questions:

1. Do I fill those gaps with a backing plaster/Skim plaster or ready made fillers. If so, will I need to PVA that area before skimming?

2. I will simply be painting the ceiling on completion of skimming the walls without any work needed on the ceiling, but I am in a quandary regarding scrim tape in that area as I don't want to put scrim onto the ceiling. Is it a simple case of putting the scrim tape on the board to the line of the ceiling (not creasing it)?

Any help appreciated.



Hi Tony

Wherever the gaps in plasterboard are they need dealing with. As a very general guide:

2-5 mm gaps can be dealt with simply by applying scrim tape, then once you've mixed your plaster up - before you start applying the 1st coat work some plaster through the scrim tape and into the gap behind - this will ensure the extra thickness has a bit longer to firm up and will not sag when on the finishing stages later on. Flatten with your trowel so that no plaster is proud of the scrim tape.

5 - 10mm gaps - apply scrim tape then mix up enough plaster just to fill gaps (Bonding Coat or finish plaster). Work the plaster really well into the gaps behind the scrim tape and then apply a second layer of tape. If it doesn't stick properly a very thin smear of plaster will allow scrim to be pushed into it. Then flatten plaster to ensure nothing is proud of the scrim tape.

10mm plus Dampen or apply PVA to any raw edges. Work some Bonding Coat Plaster onto edges - just a thin smear and fill as much of the gap as possible. If it falls through then move on to next step - where you can apply a layer of scrim tape. Then push more plaster in to fill gap and then another layer of scrim tape. Repeat this process of filling and taping as many times until gap is adequately filled.

If you will be skimming straight away all will now be fine - but if you leave it any length of time and it dries out - then damp down with water prior to skimming.

Working up to the ceiling - ensure the plaster you use for filling is kept flat at the edges where it meets the ceiling. When applying the scrim tape take care to butt the edge of the tape up to the ceiling. As the plaster firms up then further flatten this edge and remove any plaster that has spilt onto ceiling. Add more scrim tape if it has moved away from the ceiling again ensuring it butts up to the ceiling. As you are not wrapping it around the corner there is a very slight risk of cracking, but this will just be a very thin crack line right in the corner that can be easily filled with a flexible decorators caulk. When skimming keep it flat on this edge and when you trowel up in stages 4-6 remove any plaster from the ceiling with your trowel and form the corner with your brush. Using a wet brush as the plaster firms up will remove any unwanted plaster from the ceiling, fill small holes and give you a nice clean edge.


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Jul 23, 2020
Scrim on plasterboard lathe's
by: Don

Do I have to scrim the joints if I use plasterboard lathe's as opposed to 1200 x 2400 plasterboard sheets when plastering.

Jun 17, 2020
great advice NEW
by: pete

Paul ,your the man. Iwas getting in a pickle with same problem ,cheers

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