Building advice pls – fixing plasterboard to brick

I need to fix some Fermacell (like a tough version of plasterboard) to the party wall in our attic and would be grateful for a quick critique of my plan. Not sure if the neighbours heat their side, so going to add 50mm Celotex onto the brickwork then screw through that and the fermacell. Because of the insulation I can’t (I don’t think) just dot&dab it. My plan to avoid hitting mortar gaps is this:
– hold celotex and board in place temporarily somehow,
– use laser level to mark out mortar lines onto board (by looking at the bricks outside the board are),
– drill through the lot, into the brick, and bang some hammer-ins in. Probably do 3 or four across the top first before continuing drilling the rest.

Does that make sense or is there a better way?!

Cheers

Pretty sure you can dot and dab it.

Dot and dab

Why not just build off with studs, pack everything with bats then plasterboard. Insulation boards will be a nightmare to fit round the edges where the rafter are close to the wall.

And put the vapour barrier where it needs to go obviously.

Simpler might be screw wooden battens into the brick. celotex between the battens, plasterboard screwed into the batten over the top

Plasterboard on our downstairs walls is dot & dabbed. Getting/mixing plaster in the loft could be a hassle so I’d go for stud filled with insulation and board screwed to studs as mentioned above

Dot and dab pre mix keep the lumps evenly sized use anything to size it a cheap bucket trowel will do. Loads of dabs 50mm away from the edge to stop it slopping out don’t be afraid to fill in the edge after the board is on and level

Edit..
If the insulation is super level a fire retardant intsant grip will do for plasterboard works out a bit spendy but less mess

I did similar to your plan OP. I went through a few options and screwing through the lot worked out the best for me. You can dot and dab insulated plasterboard but using screws lets you use normal board an insulation which is cheaper and easier to handle. Rather than hammer ins I used Screw-Tite screws which will screw into masonry. You need the right size pilot hole but they screw in nicely. These:

https://www.screwfix.com/p/screw-tite-pz-double-self-countersunk-screws-5-x-100mm-100-pack/37146

Went up easily and it’s been up for years now without issue

If you batten the wall theres no guarantee its going to be flat, a bow or bulge will be shown on the finish.

Dot and dab you can take up any differences.

That said dot and dab isnt a very strong fixing so I would use the battens, and a spirit level, with packers where needed.

Nailing – you need galvanized tacks.

For screws you need one of these(Costs under a tenner)Called a drywall bit.

Thanks all. Don’t know why I hadn’t thought of putting battens up – seems much easier so think I’ll go with that! Surprised the dot&dab stuff will stick to the foil surface on the celotex, but even so it sounds messy. Much happier with wood and screws! It’s not a massive wall so should be able to set the studs flat/straight.

If I foil tape over the studs to join the celotex I should be ok without vapour barrier… right?

Not quite the same usecase but when I did our garage conversion I screwed celotex to battens, used foil tape on the joins then over the screw heads then used pink foam to stick the plasterboard to the foil insulation. I was sceptical at first but it was remarkably easy to use.

The non insulated side of the room I used standard plasterboard straight onto the masonry with dot dab which I found really hard just for the sheer volume of adhesive you need to mix and the speed you need to go at. The pros make it look easy and I’m sure it is but it’s tough work for a furloughed IT consulatant

https://www.sealantsandtoolsdirect.co.uk/everbuild-pinkgrip-dry-fix-fr-dryfix-plasterboard-installation-foam-dryfix7?language=en-gb&currency=GBP&gclid=Cj0KCQiA8ICOBhDmARIsAEGI6o04BNyKc5Z7CLmSwxmYh2Z0dP4nOxwwQzQYao3XGfZyg39iFsVHfGQaAjuMEALw_wcB

if your dot and dabbing mixing up a bag at a time of driwall adhesive is hard to do and get the right consistancy without a good proper mixing drill, a normal drill with a small paddle isn’t enough. even the cheap mixing drills don’t tend to last long mixing driwall.

bought one of these https://www.screwfix.com/p/belle-group-promix-1600e-electric-paddle-mixer-230v/17635 (110 version)when i went self employed and couldn’t even try and guess at how many tons of plaster its mixed up. only needed a switch and brushes and still going strong after 16 years.

in the op’s case i would just batton or stud of the wall.

Surprised the dot&dab stuff will stick to the foil surface on the celotex

not so sure it would, never tried and wouldn’t but it does stick insulated plasterboard where there is no foil surface.