How to go about plasterboarding an angled ceiling?

[Mark A]

We have 270mm of rockwool in the loft, but that part of the ceiling where the roof truss forms part of the ceiling is just 10mm polystyrene backed plsterboard and a 70mm or so airgap, then the roof felt and slates. So must be losing a fair bit of heat through there.

I was thinking of battening it out with 40mmx40mm timber and then putting 40mm kingspan between and plaster boarding over the top. I have 5 sheets of Kingspan I need to use up and this seems like a good way of doing it. It's still not great, but better than 10mm insulation.

My main concern is how would I go about making sure the skim doesn't end up cracking along the line where the plasterboard will meet the existing painted plaster?

TIA

 

[davido_labido]

you use metal strip things, not sure what they are called, but they basically make the corner for you then you plaster over them....

il find out the name of them from my mate (who is a plasterer)

 

[AshD93]

you use metal strip things, not sure what they are called, but they basically make the corner for you then you plaster over them....

il find out the name of them from my mate (who is a plasterer)

Angle bead?

 

[danny77]

My main concern is how would I go about making sure the skim doesn't end up cracking along the line where the plasterboard will meet the existing painted plaster?

Use scrim tape over the join and when you skim the new boards carry on past the join a few inches and blend in to meet existing plaster

 

[Maccapacca]

Not really curved though is it, looks to me to be flat with the joint being tapered.

You may have something though, could you just stick the insulation to the original plaster then stick the board to the insulation, bet the right stuff is out there somewhere.

Save all the bother of battening out and get the most out of your insulation. Then scrim the one joint.

 

[danny77]

It could be done that way, first find and mark where timbers are under existing plaster, glue insulation boards on or even just put a few screws in to hold it in place until the plasterboard gets put on and then just use long drywall screws to secure plasterboards to timbers

 

[mattyfez]

Couldn't you just inject the space with expanding insulation foam?

 

[Maccapacca]

You need the ventilation above and it sounds like the space is just the depth of the joists.

 

[Mark A]

I like the sound of glueing the insulation straight to the plaster, would certainly be a lot easier. The insulation is Kingspan 40mm, with foil on both sides. Are there any products out there that will glue the insulation in place? I have loads of expanding foam or 5 minute polyurethane glue if that will do.

Or what about gluing a layer of foam onto the plasterboard and then screwing battens over the top into the joists behind and then add more insulation between the battens?

 

[Maccapacca]

Danny77 has it spot on just use long enough screws to bite into the joists from the platerboard, you can use washers if you want and wind them right in and fill or skim over the top.

 

[Mark A]

Thanks, i'll probably get one with it this weekend. Really need to get these sheets of insulation out of the way.

 

[ANDARIAL]

It could be done that way, first find and mark where timbers are under existing plaster, glue insulation boards on or even just put a few screws in to hold it in place until the plasterboard gets put on and then just use long drywall screws to secure plasterboards to timbers

What this man said
Only Way To Be Sure

 

[Mark A]

Stage 1 complete. Glued it in place with expanding foam and put some 80mm screws with washers into the timber behind.

I used rare earth magnet to locate the nails that hold the studs in place to find the studs and it worked amazingly well. I should be able to screw the plasterboard into the ceiling studs at the very top with normal 40mm drywall screws and then just use some long screws to fix it at the bottom and middle.

One question about the plastering: Will I have to sand the emulsion paint off the ceiling where the scrim tape will be joining the plasterboard to the ceiling?

 

[Maccapacca]

Looking good.

No not really, maybe at a push 'key' it up with some course paper.

 

[ANDARIAL]

What we do is mix a 50/50 pva and water and `paint` this onto the ceiling/walls before applying plaster(let it dry or plaster slides off)

 

[valve90210]

How did this turn out in the end? And did it have much of an effect on the heat loss?

I have the same situation with the angled ceiling and am contemplating doing the same at some point.

 

[Mark A]

Still not got around to plaster boarding it yet due to other more pressing jobs . It's definitely made a difference though. When I was putting the sheets up I could feel the heat reflecting from the foil and with it being directly under the radiator it should help stop the heat going straight outside.

Ideally I'd have put 2 layers on there to make 80mm, but I think it might look a bit odd with a large angled ceiling area.

I'll hopefully get some time to get it plastered etc soon and i'll post some pics. Then if it turns out ok i'll do the whole of the upstairs as I still have 4 sheets of insulation that need using up.

 

[Mark A]

Completed one of the rooms today. It was my first proper go at plastering and it didnt turn out too bad. Had to do just one coat instead of two as the plaster went hard by the time i'd put the first coat on and it was too late to start mixing more. Hope this wont cause any problems. Would it be ok to add another coat tomorrow or will it be ok with 1 coat?

Its just a box bed ceiling that will be painted matt white, so doesnt need to be perfect. I started on this room despite it being the hardest, so I could practise before doing the other rooms.

 

[valve90210]

Looking good!!! Might have to add that to the ever growing list of jobs to do in my house, like yours we have angled bits which have nothing to insulate and they get rather cool!!!

 

[ANDARIAL]

If plaster is old it will go off quicker
also if it is too dry/not enough water and the room is warm it will go off quicker too
If you plan on putting on a second coat now let it dry at least a day or two,then prime the area with 50/50% pva first.let dry then skim(that is what our plasterers do anyway)