Sat, 17 Oct 2026 16:08:25 +0100 https://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1398&Focus=16166#Comment_16166 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1398&Focus=16166#Comment_16166 Thu, 13 Mar 2008 19:19:40 +0000 ps_mrwonderful
Its 100mm insulation plus 12.5mm plasterboard, going on to a skeiling. I assume screwing it on is better than dot and dab, but am unable to find long enough screws (150mm probably required to allow the end to get into the rafter).

Any ideas? Surely someone else has come across this before?
Ta!]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1398&Focus=16168#Comment_16168 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1398&Focus=16168#Comment_16168 Thu, 13 Mar 2008 19:27:23 +0000 tony
Screws are made long enough but they are expensive. I use plastic nails]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1398&Focus=16174#Comment_16174 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1398&Focus=16174#Comment_16174 Thu, 13 Mar 2008 19:58:59 +0000 ps_mrwonderful https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1398&Focus=16184#Comment_16184 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1398&Focus=16184#Comment_16184 Thu, 13 Mar 2008 20:36:35 +0000 funcrusher https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1398&Focus=16208#Comment_16208 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1398&Focus=16208#Comment_16208 Fri, 14 Mar 2008 00:08:27 +0000 Mike George http://www.british-gypsum.com/products/plasterboard___accessories/gyproc_fixings/gyproc_nailable_plugs.aspx As you can see these ones are not long enough nor suitable as a timber fixing.

The thickest boards I have fixed to rafters were 40mm PUR with a 12.5mm laminated plasterboard- I used 100mm drywall screw as they are treated so as to avoid the staining Tony mentions. I don't think they make drywall screws longer than 100mm

I would consider taking down your existing ceiling and cutting the insulation you have bought between the rafters, leaving a clear 50mm ventilation gap on the cold side of the insulation. Don't try and cut them tight- instead leave a 5-10mm gap either side of each board, temporarilly wedge, and then fill the gaps with expanding PUR foam. Then put a polythene sheet fixed underneath and then plasterboard over and skim.

EDIT: My final paragraph assumes the existing rafters are deep enough to allow the full thickness of the boards plus a 50mm airgap. If not you may need to 'plant on' timbers to the existing rafters to make up the difference.

Hope this helps]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1398&Focus=16298#Comment_16298 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1398&Focus=16298#Comment_16298 Sat, 15 Mar 2008 09:13:06 +0000 jamesingram
Jim]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1398&Focus=16308#Comment_16308 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1398&Focus=16308#Comment_16308 Sat, 15 Mar 2008 11:50:03 +0000 tony
Never seen a glass hammer. Or was it a hammerfur?]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1398&Focus=16310#Comment_16310 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1398&Focus=16310#Comment_16310 Sat, 15 Mar 2008 11:58:08 +0000 James Norton
J]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1398&Focus=16411#Comment_16411 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1398&Focus=16411#Comment_16411 Sun, 16 Mar 2008 18:01:58 +0000 jamesingram were you never sent to get a long weight in your apprentice days Tony

But Plastic nails? never used them , unless you mean the external insulation fixings
, got a supplier/manifatures name

I've been using long screw with washers and 3mm ply strips to fix thick PUR/pb board on to the rafter, I realise the thermal bridging problem
but I've yet to come up with a better idea,
contact glue could work If you could get some level rafter ( loft conversions so retrofit mainly)
but I cant help sticking screws in everywhere ,belt and braces approach


cheers Jim]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1398&Focus=16473#Comment_16473 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1398&Focus=16473#Comment_16473 Mon, 17 Mar 2008 11:31:01 +0000 ps_mrwonderful https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1398&Focus=16479#Comment_16479 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1398&Focus=16479#Comment_16479 Mon, 17 Mar 2008 12:01:59 +0000 Jeff B
Jeff B]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1398&Focus=17352#Comment_17352 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1398&Focus=17352#Comment_17352 Thu, 27 Mar 2008 22:53:24 +0000 Mike George https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1398&Focus=17377#Comment_17377 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1398&Focus=17377#Comment_17377 Fri, 28 Mar 2008 10:50:17 +0000 ps_mrwonderful https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1398&Focus=17394#Comment_17394 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1398&Focus=17394#Comment_17394 Fri, 28 Mar 2008 14:31:42 +0000 Martian Have a look at some of the fixings here:
http://www.wbs-ltd.co.uk/renders_beads.htm
look at the "SBH-T 65/25" and TERMOFIX 6H]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1398&Focus=17401#Comment_17401 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1398&Focus=17401#Comment_17401 Fri, 28 Mar 2008 16:32:57 +0000 Joinerbird
I went off to buy a "fixed bubble level" back in the days, but was too quick for the skyhooks and glasshammer]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1398&Focus=17404#Comment_17404 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1398&Focus=17404#Comment_17404 Fri, 28 Mar 2008 16:42:15 +0000 ps_mrwonderful https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1398&Focus=19574#Comment_19574 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1398&Focus=19574#Comment_19574 Tue, 29 Apr 2008 12:45:02 +0100 dachaidh https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1398&Focus=19858#Comment_19858 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1398&Focus=19858#Comment_19858 Fri, 02 May 2008 16:19:40 +0100 Mike George Posted By: MartianI wonder if the sort of fixings used to fix external insulation to walls would also work in this application.
Have a look at some of the fixings here:
http://www.wbs-ltd.co.uk/renders_beads.htm" rel="nofollow" >http://www.wbs-ltd.co.uk/renders_beads.htm
look at the "SBH-T 65/25" and TERMOFIX 6H

They would work to fix the boards, but I am not confident that plaster would remain adhered to them. They would also have to be flush finished with the face of any plasterboards and doing this would likely damage the boards in a way that defeats the objective.

I have considered using these in the past, but have dismissed them because of the above risks, They are also a bit on the expensive side.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1398&Focus=32843#Comment_32843 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1398&Focus=32843#Comment_32843 Tue, 16 Sep 2008 00:28:10 +0100 michael1924 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1398&Focus=32848#Comment_32848 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1398&Focus=32848#Comment_32848 Tue, 16 Sep 2008 07:52:02 +0100 Mike George http://www.evolutionfasteners.co.uk/pdfs/downloads/catalogue08.pdf Says will fix up to 90mm of material so longer than those I have used previously. Are there other ones that I have missed?

My only other query would be whether they are designed to be plastered over, as some fixings leave surface staining. Will contact their technical department]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1398&Focus=32912#Comment_32912 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1398&Focus=32912#Comment_32912 Tue, 16 Sep 2008 22:51:09 +0100 abomb1969
Why "leaving a clear 50mm" airgap? I have just got some 150mm Kingspan from seconds&co. My rafters have 125mm and my architect specced 25mm airgap under the membrane. When I told him I had got this insulation cheap he said I could reduce the airgap to 10mm to get more of the insulation in the rafters, leaving 35mm under the rafters. Any input appreciated, I was going to put a 10mm batten behind the roof membrane to hold the insulation off the membrane a bit.

Adding battens to beef up the rafters will create a cold bridge, my architect suggested filleting in a 35mm deep strip of board and screwing through this with the board held off the screws.

The comment about adding a layer of polythene sheet over the insulation is a good one.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1398&Focus=32922#Comment_32922 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1398&Focus=32922#Comment_32922 Wed, 17 Sep 2008 08:06:20 +0100 Mike George