I have some excess gap sealant on a plasterboard joint on the ceiling. I used the sealant to fill a 5mm crack as a result of the house settling. The problem is that the sealant isn't quite flush with the ceiling. I have tried a random orbital sander, but it doesn't do a very good job of sanding it down. A belt sander would tear the sealing apart? Does anybody have any methods? Thanks!

I assume that you have used a product like Selleys No More Gaps unfortunately this products cannot be sanded you need to ensure that you remove any excess before the product skins. A sander is likely only to tear the filler. You may be able to use a stanley knife or razor blade scraper.

yep you'll have to scrap that or knife it till its flush again

If it's a hard set, plaster like compound, you can sand, but a coarse paper helps (100 grit) and you do have to be careful not to scuff up the cardboard face of the plasterboard. I've used an orbital, but having a vacuum cleaner attached is a good idea unless you like cleaning the rest of the room.

If it's a flexible filler, use a sharp knife to vee cut it out and re-do. Cornice cement is a good, solid, quick setting first coat (ever-so-slightly underfill) and when that has set, top with top coat or other easy to sand filler. Try not to sand too much, as it damages the board and you end up having to coat it again to get rid of the fluffy cardboard bits!

The idea way is to smooth it out with the trowel, let it set, then just lightly scrape off any rough bits and paint! (at least, that's what the seasoned pros do!)

See Rod's site How to plaster, plastering tips, plastering cracks, holes, for all the gory details

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The real answer is to cut it out and repair the crack properly. Refer to this thread below. Repairing joint cracks new(ish) house

Cracks in plasterboard joins cannot be repaired with no more gaps and be made invisible. I would cut it out and scrape back enough of the paint and topcote to create a shallow reccess to take a paper tape, I use an old chisel and scape it back to the base coat about 50mm wide. It is not that hard once you have the right knack. Wet the reccess you have created before applying the paper tape this will help the tape adhere to the base coat and prevent dry spots under the tape. The wet join stops the dry plaster sucking the moisture out of the base coat before you can get the tape bedded.

There are really no short cuts to repairing a cracked plasterboard join. I have used and still do now and then, wet and stick paper tape over plasterboard join cracks. This works ok but I have gone back to scraping out a shallow rebate as it does do a better job.


Cheers Rod

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