Use Beading around window reveals?

Pauley2

Hi,

I'm about to insulate a room with foil backed insulated plasterboard (which is the correct type as far as I can make out from the various manufacturer sites) and which I'll attach directly to the current (1970s) plaster on hollow block wall with "mushroom" fixings.

I'm pretty much ready to get going, but the only thing I'm unsure of is how to handle the window reveal edging.

At the room-side reveal edge, do the drywall pieces simple butt up against each other at 90deg and do I use "mud" to finish off? OR should I try to get the tapered edge of the plasterboard sheets to line up with the reveal and embed "L" shaped beading to strengthen the edges. What's standard practice?

Also - what's standard practice to deal with the (new) plasterboard to existing ceiling junction? I was going to tape and feather (more work), rather than caulk (quick and easy), which no matter what the tube says, always shrinks and leaves a crack. Again what's standard practice? - or can anyone recommend a really good shrink resistant caulk...?

Thanks!

kkelliher

Pauley2 wrote: »

Hi,

I'm about to insulate a room with foil backed insulated plasterboard (which is the correct type as far as I can make out from the various manufacturer sites) and which I'll attach directly to the current (1970s) plaster on hollow block wall with "mushroom" fixings.

I'm pretty much ready to get going, but the only thing I'm unsure of is how to handle the window reveal edging.

At the room-side reveal edge, do the drywall pieces simple butt up against each other at 90deg and do I use "mud" to finish off? OR should I try to get the tapered edge of the plasterboard sheets to line up with the reveal and embed "L" shaped beading to strengthen the edges. What's standard practice?

Also - what's standard practice to deal with the (new) plasterboard to existing ceiling junction? I was going to tape and feather (more work), rather than caulk (quick and easy), which no matter what the tube says, always shrinks and leaves a crack. Again what's standard practice? - or can anyone recommend a really good shrink resistant caulk...?

Thanks!

There are many ways to do the window joint. I know xtratherm have a premade special window reveal which matches the insulated board and deals with this issue. I have seen where the joint is motred from both sides like you would with two pieces of skirting board meeting at a corner or you could bead it as standard.

In respect to the ceiling, you generally would get away without any major work in this area as the skim will finish this for you naturally (I did not treat this area in a room myself and it has never cracked or moved in any way a couple of years later) however you could again put a bead at the ceiling joint if you were worried about it

Pauley2

Thanks for that info. I'll probably go with the corner bead.

On a side note, I went through a NIGHTMARE ordering the panels. Confusing information and conflicting advice from manufacturer. Multiple brand names for the same thing. (THREE different names being used between the manufacturer and the local supplier). Items listed in manufacturers brochures that dont exist...

AAAgh!

One more question:
EVERYTHING I've read so far in brochures and heard from tech support says to use FOIL backed when putting in direct contact with existing plaster (and foil backed is what I tried VERY hard to order), However, for the lesser thickness panels that I need in certain places, the only option is PAPER backed - which technicaly doesnt seem to be recommended for direct contact with plaster, yet it's all I can get.

I'm concerned about the vapour barrier not being in the right place and mold getting a foothold on the paper, should there be any future moisture ingress in this hollow block wall.

The sales people and counter reps tell me not to worry, but as this is my mothers bedroom I'd like to be a bit more assured. Can anyone with exprience of this put my mind at ease?

Thanks!

L1979

Pauley2 wrote: »

Thanks for that info. I'll probably go with the corner bead.


One more question:
EVERYTHING I've read so far in brochures and heard from tech support says to use FOIL backed when putting in direct contact with existing plaster (and foil backed is what I tried VERY hard to order), However, for the lesser thickness panels that I need in certain places, the only option is PAPER backed - which technicaly doesnt seem to be recommended for direct contact with plaster, yet it's all I can get.

I'm concerned about the vapour barrier not being in the right place and mold getting a foothold on the paper, should there be any future moisture ingress in this hollow block wall.

Speaking from experience with Xtratherm!

Foil is Vapour Control layer.
If mechanically fixing to wall you want foil backed.
If dot and dab, you want paper back! But the Vapour Control Foil Layer is immediately under paper backing. so

Paper-Foil-insulation-foil-plasterbaord

Mechanical Fixing in both applications should be metal, for Fire Regs.


On your other question!
http://www.kingspaninsulation.ie/Products/Kooltherm/Kooltherm-K17-Insulated-Plasterboard/Overview.aspx
Download Pdf and window detailing is on page 9.

Enjoy

Pauley2

Yes, "XtraTherm" got it in one!

Drove me nuts, not to mention the fact that foil backed is NOT available in the smaller sizes, despite what the brochures say..

Anyway, thanks for that. I'm finally ready to proceed.

Cheers..

Pauley2

A few more questions (!).

So I got a tub of "joint cement" which I thought would handle all the joints (obviously) and the corners with the bead, however, I just noticed on the tub it says "not suitable for bedding corner protection". What??

What am I supposed to use, then to bed the bead (metal mesh type)? and once "bedded" do I then finish off with the joint cement?

Also, when I did this before, it was with uninsulated plasterboard over a wood frame, so I was able to secure any corner bead with a drywall screw into the frame behind it. Now, with the insulation being so thick and no wood behind I'm not sure how to secure the bead, particularly along the long horizontal runs at the top of the window reveal. What's the norm to secure the bead in this situation? (Alternatively I was thinking of using the joint tape with metal/foil embedded in it that I've seen in DIY manuals, but no-one seems to stock it.)

Lastly, being as the metal mushrooms are going direct into the block behind and may transfer some cold and/or moisture to the mushroom head and possibly cause later discolouration of the finish, I was thinking of coating them with either PVA or some "Primer/Sealer stain killer" (water based) that I have left over. Good/bad idea?

Thanks