April 16, 20233 yr Author When I say 120mm Rockwool, think I will going 2 x 60mm rocksilk as suggested
April 16, 20233 yr 19 minutes ago, richo106 said: how many screws per PIR would people allow? Would 12 be enough? Do I have to ‘join’ them on a rafter like plasterboard I've never done this so I don't know but I'd say the 25 x 100mm strapping will take care of the load so all you need is a screw or two to hold it until it's taped. Joints on the rafters would be better but I wouldn't cut boards to achieve this. Keep us updated with pics.
April 16, 20233 yr 1 hour ago, richo106 said: how many screws per PIR would people allow? Would 12 be enough? Do I have to ‘join’ them on a rafter like plasterboard? Just pin the board on with 125mm screws and a penny washers 2/3 per board then 200mm screws through the batons, I did 400 centers (I think). So much easier if you can follow the rafters as it holds the ends tight.
April 16, 20233 yr Author 5 hours ago, Iceverge said: I've never done this so I don't know but I'd say the 25 x 100mm strapping will take care of the load so all you need is a screw or two to hold it until it's taped. Joints on the rafters would be better but I wouldn't cut boards to achieve this. Keep us updated with pics. Thanks again, yes I will keep updated. This is it currently
April 16, 20233 yr 34 minutes ago, richo106 said: Thanks again, yes I will keep updated. This is it currently What are those metal things on the gable wall?
April 17, 20233 yr I've battened out a couple of rooms now using 2x1 battens. All seem to be holding well, the only problem I've had is having to screw quite close to the PB edge so you run the risk of crushing the PB edges if you're not careful. A decent PB screw bit has helped me though. If I didn't already have a load of 2x1, it would have been much easier with wider battens.
April 17, 20233 yr 8 hours ago, ETC said: What are those metal things on the gable wall? restraint straps, requirement of building regs. bit close together though.
April 17, 20233 yr 59 minutes ago, Dave Jones said: restraint straps, requirement of building regs. bit close together though. They don’t look long enough or thick enough for LRS. Plus they need solid timber blocking between them. Wha5 centres are those rafters at?
April 17, 20233 yr Author 2 hours ago, ETC said: They don’t look long enough or thick enough for LRS. Plus they need solid timber blocking between them. Wha5 centres are those rafters at? Rafters are at 600 centres I will make sure I put some solid timber (got some spare rafter timber) between the restraint straps, thanks for that.
April 17, 20233 yr Author 6 minutes ago, ETC said: LRS need to be 30mmx5mmx1000mm long at maximum 2000mm centres. I will check this, many thanks
April 17, 20233 yr Author Regarding battening and plasterboarding Would people recommend battening horizontally at 400 centres (using 3 x 1" timber) Would then using a single 12.5mm standard wallboard be OK to board the ceilings with? Or would it be better to batten vertically (to follow rafters at 600 centres) and use 15mm wall board? Any advice greatly appreciated Many Thanks
April 17, 20233 yr 5 minutes ago, richo106 said: Regarding battening and plasterboarding Would people recommend battening horizontally at 400 centres (using 3 x 1" timber) Not really. For what reason? Would then using a single 12.5mm standard wallboard be OK to board the ceilings with? Yes. Or would it be better to batten vertically (to follow rafters at 600 centres) and use 15mm wall board? Not required unless your rafters aren’t deep enough for the insulation. Just make sure you retain a 50mm air space above the insulation. Any advice greatly appreciated Many Thanks
April 17, 20233 yr Author 5 minutes ago, ETC said: I will having insulation (rockwool type) between the rafters and then 100mm PIR underneath so was going to use the battens to firmly hold the PIR on and give me a batten for the PB to fix to and a service void if needed Or i could just screw the plasterboards direct to rafters (through PIR with 150mm drywall screws) Many Thanks
April 17, 20233 yr 9 hours ago, ETC said: They don’t look long enough or thick enough for LRS. Plus they need solid timber blocking between them. Wha5 centres are those rafters at? yep, they normally fix to the bracing for obvious reasons.
April 23, 20233 yr Author I have pushed my PIR tight up to my block work when laying the PIR over the rafters. Would people recommend using airtight tape from the PIR to the blocks to make a perfect seal? If so, what tape would you recommend? Many Thanks Edited April 23, 20233 yr by richo106
April 25, 20233 yr Author I have just had a meeting with my BC officer (a new one for my job) and he is not happy with the slab insulation between the rafters no matter how I much i tried to put my case across. To keep everyone happy I am now installing 100mm between the rafters and 100mm underneath (I have already cut some 100mm so cheaper to do it this way) When I fit in them between the rafters do I have to foam and tape over the joints or just foam and tape over the 'top' (under the rafter) layer? Slightly annoyed about this as I spent all Sunday doing one room but he was not having it and not worth the argument this time Many Thanks
April 25, 20233 yr Just now, richo106 said: have just had a meeting with my BC officer (a new one for my job) and he is not happy with the slab insulation between the rafters no matter how I much i tried to put my case across. Why? Here's a detail from Knauf showing just this.
April 25, 20233 yr i put 190mm glass wool batts between my rafters with 100mm PIR below and my BCO said it was fine. is your BCO saying that he wants PIR between the rafters? if so i didn't think they could mandate what insulation was used as long as you hit the regulation U-values and it has a BBA certificate it should all be fine.
April 25, 20233 yr Author I tried to explain to him and shown him some examples, his concern was how does he know a 50mm air gap was maintained throughout? And he has never signed a vaulted ceiling off that didn't use PIR between the rafters I decided this wasn't a battle worth pursuing and it would only take me a day to correct so thought best to keep him on side as he will be looking after my project to the end now
April 25, 20233 yr 11 minutes ago, richo106 said: I tried to explain to him and shown him some examples, his concern was how does he know a 50mm air gap was maintained throughout? And he has never signed a vaulted ceiling off that didn't use PIR between the rafters I decided this wasn't a battle worth pursuing and it would only take me a day to correct so thought best to keep him on side as he will be looking after my project to the end now how does he know the 50mm air gap is maintained with PIR? i assume it's because the PIR is flush with the rafters....therefore it's the same argument for mineral wool! Although i didn't have to worry about the air gap as we fully filled and had the air gap above the rafters using battens and counter battens.
May 1, 20233 yr Author Hi all I have made a start on my vaulted ceilings. I now have 100mm PIR in between the rafters and 100mm PIR underneath. I have taped all my PIR joints with foil tape, I have foamed the edges of the boards and plan to air tight it to wall plate and block wall. Will this be sufficient for air tightness or is it best to put a vcl over my battens and them tape that the wall instead? My plan was to just use a VCL strip down the middle bit
May 1, 20233 yr Author 2 hours ago, Iceverge said: That'll be fine. Tidy work. How was fitting the PIR between the rafters? Yes the PIR wasn’t too bad when I got going with it. Is it best to air tight tape the PIR to the block work and wall plate or is it not needed?
May 2, 20233 yr 8 hours ago, richo106 said: Yes the PIR wasn’t too bad when I got going with it. Is it best to air tight tape the PIR to the block work and wall plate or is it not needed? Good to hear. Yes seal it to the blockwork. Tape won't work unless you prime it.
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