skimming a ceiling

by Alan Gibson
(New Cumnock, Scotland)

What mix do you use for skimming a ceiling? Is it stiffer than for a wall?

Answer
Yes so that it is a bit easier to control - but not too thick that it makes it difficult to spread thinly and keep flat.

Long Ceiling

Hi, Just bought your online video and it has some great tips.  Will be plastering a workshop at the back of the house (hopefully) with some good results over the next few weekends. Now looking forward to it more than I was.

All the areas I have to plaster are plasterboard. I am assuming thistle
board finish is ideal and I have no need to PVA/wet the areas.

I have a fairly long ceiling in it that I will need to plaster.   It is about 2.7m by 8m and is all one area.  Suggestions would be appreciated.

Do I need to use scrim tape at the point where the ceiling and wall meet each other. Would this stop cracking at this pooint or would it be more beneficial to force plaster between the two surfaces?


Thanks for your help.

Answer

Hopefully won't confuse you with the information below. Just get back to me if you're unsure.

Thistle multi-finish is best due to a slightly longer setting time. Also can be used on every surface, meaning in the future, you don't have to get use to another plaster which behaves slighty differently. There is no need to apply PVA to the boards.

The main problem may be the size - which may be to large to get done in one go. But you don't want to do half, then when it has set do the other half, as you will see the join.

The following may help:

Coping with bigger areas

After you have practised on a few walls you should find that your speed rapidly increases. Even then big areas can pose problems, but do not mean they cannot be undertaken – for very large areas it may be necessary to split the ceiling up into sections. Advancing each section a stage at a time – means that you have a series of wet edges. If one section is only one stage behind the other then rather than having a definite join the twosections will easily merge.

By mixing up the skim plaster in different batches means the different
setting times can be used to your advantage...

One example of using this method is (the sections can be as big or as small as you can cope with)....

1. mix up 1 batch – enough to 1st coat the 1st section

2. mix up another batch – enough to 1st coat the 2nd section

3. flatten off the 1st section

4. mix up another batch – enough to 2nd coat the 1st section and 1st coat the 3rd

5. then 2nd coat the 2nd section and 1st coat the 4th

6. stage 4 (1st trowel (fill in holes)) on section 1 and 2nd coat the 3rd

7. stage 4 on the 2nd section, stage 5 on the 1st section etc, etc ..

It can get a bit confusing as to remember exactly where you are but the situation will arise where the first section may be set and finished before you have completed the area but with a series of wet edges you keep advancing each section a stage at a time.


Scrim tape - for small gaps no problem to put scrim tape on first - but do not wrap around the corner. In case of movement it is better to butt the
tape up to each edge then if anything moves in the future you can fill a very thin crack with flexible decorators caulk, rather than risk the scrim tape being pulled off due to movement.

But for larger gaps push plenty of plaster in first then apply scrim to wet plaster and smooth off. For any areas of concern 'bonding coat' and a few layers of scrim will ensure no cracking.

Good Luck

Paul

ceilings

by barry hobbs
(thetford norfolk)

Hi ya , ive never done plastering before and had a go at the walls ,,not too bad so tryed a ceiling lol bit bumpy , do you have a sloppy mix for the ceiling and can i try and go over what i have put up , if so do i have to seal the 1st coat ? and if i apply a second coat on the walls do i have to seal them please . Barry

Answer
If anything the mix may be slightly thicker - just so it doesn't all fall on your head!
You need to PVA it and go over all the stages again completing everything before it sets.
Paul

bumpy artex ceiling

by mick
(sheffield)

can i plaster over a bumpy artex ceiling with cracks in it and how many coats do i need to apply if any so it's smooth?

Answer

Just apply PVA first. Then run a thin smear of plaster over the cracks and push some reinforcing mesh (scrim tape) over.

If the ceiling is just a bit bumpy then apply the first coat as thickly as possible. Then when firm flatten before 2nd coating. If after the 2nd coat it is still not flat then just apply a 3rd coat.

If the ceiling is really bumpy then it can be easier to apply bonding coat and when firming up flatten all ridges off with your trowel. Then leave to set - so you need to make sure there are no ridges left, particularly in the corners. Then skim as normal with 2 coats.

Ceilings

Hi Paul,

Plasterings been going well and have done some good jobs but there's always bits I'm not happy with (other people who don't plaster prob wouldn't notice though). A few questions:

I put up a new plasterboard ceiling of about 14 sq metres and plastered. Once plastered I've noticed that the edge of the ceiling where it meets the wall isn't as flat as I would like, giving a sort of wavey line. Would you hold up a feather edge to check flatness of the ceiling at the edge or somehing like that? How do you get a decent flat line where the ceiling meets the wall? Are there any tips to get a decent flat ceiling, especially at the edges/any general ceiling tips as I find them a lot harder than walls.

Also on a new plasterboard ceiling would you still typically put on 2 coats of plaster or do it with 1 as I found getting 2 coats on a ceiling that size a challenge!

Any tips for getting the wall uniformly flat round a sunk light switch box? This might sound like a strange question but I keep finding that when I put the light switch back on, the walls slightly out making small gaps round the switch where it meets the wall (its not terrible and most people probably wouldn't notice but I know a pro platerer would have the wall flat all round the switch)

Cheers Paul,

Rob


Answer

Hi Rob
The edges are one of the most difficult aspects. One of the main reasons is due to too much plaster being there. A few things that may help:
when applying Start a few inches away from edge and then when flattening push a smaller amount right into edge. This way you'll avoid overloading the edge.
Flatten the edges after you apply by turning your trowel through 90 degrees. So if you apply by going front to back flatten by going side to side.
As soon as you have finished each stage then a quick flattening of all edges as a check.

Applying 2 coats will buy you much extra time as if the 2nd coat is very thin you are almost troweling it flat with a very thin smear of fresh plaster. If this fresh plaster has recently been mixed then you are also extending the setting time. So it can be false economy to try it in one, but if you have a good finish on the 1st coat then give it a go!

With the light switch always work out from the switch into the wall, with your trowel centrally positioned over switch. repeat this from all four aspects making sure that either end of the trowel is touching further into the wall to ensure flatness.

Hope this helps

Paul