Paddy Galore! Posted November 13, 2012 Report Share Posted November 13, 2012 (edited) hi chaps, been doing a roof and it incorporates a flatroof between two pitched roofs, the timber work isn't a problem but the spec says 100mm of cellotex on top of the ply then another skin of ply, then either fiberglass or felt. so what do i stick the insulation stuff down with please? cheers, gram. edit, normally i'd leave all that stuff to guys in the know, but it's a small builder i'm doing the work for and i don't think he knows much about it. Edited November 13, 2012 by GRAM71 Quote Link to comment Share on other sites More sharing options...
scifiden Posted November 13, 2012 Report Share Posted November 13, 2012 you can get a cold applied adhesive probably from same place u buy the cellotex Quote Link to comment Share on other sites More sharing options...
Paddy Galore! Posted November 13, 2012 Author Report Share Posted November 13, 2012 you can get a cold applied adhesive probably from same place u buy the cellotex cheers for the help, don't suppose you have a product name? Quote Link to comment Share on other sites More sharing options...
Rupert Posted November 13, 2012 Report Share Posted November 13, 2012 Long screws? Screfix do some 150mm ones,any glue will only be as strong as the bond between the foil and the foam, Can you put a 4x2 in the middle,like a noggin to fix to? Quote Link to comment Share on other sites More sharing options...
scifiden Posted November 13, 2012 Report Share Posted November 13, 2012 cheers for the help, don't suppose you have a product name? will check with the supplier we use & let u know tomoz. Quote Link to comment Share on other sites More sharing options...
artschool Posted November 13, 2012 Report Share Posted November 13, 2012 answers are in the thread. either use an adhesive or long fixings. you can download the handy guide from celotex's website. Quote Link to comment Share on other sites More sharing options...
Paddy Galore! Posted November 13, 2012 Author Report Share Posted November 13, 2012 Long screws? Screfix do some 150mm ones,any glue will only be as strong as the bond between the foil and the foam, Can you put a 4x2 in the middle,like a noggin to fix to? sorry rupert, spec says no penetrating fixings through celotex but didn't give a product to use, we were going to try sticcobond acrylic flooring adhesive but it's getting frosty! cheers anyway will check with the supplier we use & let u know tomoz. cheers mate, much appreciated, googled the main site but i can't find anything listed. Quote Link to comment Share on other sites More sharing options...
carpentermark Posted November 13, 2012 Report Share Posted November 13, 2012 (edited) hi chaps, been doing a roof and it incorporates a flatroof between two pitched roofs, the timber work isn't a problem but the spec says 100mm of cellotex on top of the ply then another skin of ply, then either fiberglass or felt. so what do i stick the insulation stuff down with please? cheers, gram. edit, normally i'd leave all that stuff to guys in the know, but it's a small builder i'm doing the work for and i don't think he knows much about it. you dont need to stick or fix the cellotex/ kingspan down mate, just lay it on and fix the ply (through the insulation) into the joists with long screws. edited: just read post saying no fixings through? ??? who wrote the spec? if its structural engineer or local authority i would be asking them for a fixing detail! they cant tell you what not to fix with without an alternative when it comes to roofs as wind shear/ deflection, weight of snow etc all comes into play! I wouldnt guess at it mate! Edited November 13, 2012 by carpentermark Quote Link to comment Share on other sites More sharing options...
Northamptonclay Posted November 13, 2012 Report Share Posted November 13, 2012 Silkaflex Quote Link to comment Share on other sites More sharing options...
beerdeor Posted November 13, 2012 Report Share Posted November 13, 2012 I would put joists of 4x2 fixed to the first layer of ply at 600 centres put your celotex inbetween then fix secondary sheeting to the joists,as has been said already if you bond it the roof will only be as strong as the bond between the foam and foil of the insulation boards hth Jim Quote Link to comment Share on other sites More sharing options...
Paddy Galore! Posted November 13, 2012 Author Report Share Posted November 13, 2012 guys, it has to be glue of some sort, says so in the spec, the building regs bod is a bit of a stickler too, and so is the boss, old school builder, i only got the job after he saw i had some proper saw horses, not those shoddy plastic/alloy folding things we had a good long chat about some of the monkeys he's had on site before Quote Link to comment Share on other sites More sharing options...
kent Posted November 13, 2012 Report Share Posted November 13, 2012 I have done this a few times and always fixed via leaving edge clearances, wedging it at the sides and foaming it all along the edges Quote Link to comment Share on other sites More sharing options...
Rupert Posted November 13, 2012 Report Share Posted November 13, 2012 While watching grand designs in the past i have seen them use an areosol adesive in a tin like exp foam (750ml) to stick insulation 300mm thick to vertical concrete,then a render was applied.I dont know what it is called dut it is also advertised as a replacment for drywall adesive in drylining applications To appear the man of the moment i would ring cellotex technical and talk to them they are usually very helpful. Quote Link to comment Share on other sites More sharing options...
Northamptonclay Posted November 13, 2012 Report Share Posted November 13, 2012 Instastik Quote Link to comment Share on other sites More sharing options...
scifiden Posted November 13, 2012 Report Share Posted November 13, 2012 Instastik that rings a bell but i will still double check tomoz. Quote Link to comment Share on other sites More sharing options...
Paddy Galore! Posted November 13, 2012 Author Report Share Posted November 13, 2012 cheers guys Quote Link to comment Share on other sites More sharing options...
jef Posted November 13, 2012 Report Share Posted November 13, 2012 You need to speak to your regs guy. I can't speak for a single membrane but if fibreglass is going down on top, the ply needs to be mechanically fixed through the insulation. As the fibreglass expands and contracts it can lift the boards if not fixed correctly. Even more important is a perimeter timber, so the edges of the roof are fixed down hard, not through a compressable material (i.e the cellotex). What you have listed is standard spec for a warm roof to take fibreglass. If it was me, there wouldn't be a guarantee issued at the end of the job without the fixings. They are usually around 170mm long with a large flange head and torx fitting, which need setting into the top board. Single membrane, such as Alwitra, may be fine with your spec, although doesnt require the top layer of ply and when I've seen it fitted they still screw down the cellotex using long screws with 2 inch washer heads. Hope this helps JF Quote Link to comment Share on other sites More sharing options...
the_commoner Posted November 13, 2012 Report Share Posted November 13, 2012 (edited) try Sikaflex, you can get it from builders merchants, if its a small area it should be ok ...... the reason that you cant use fixings is you will potentially create a cold bridge through the fixing from the outside to the inside, building control dont like these !!!!!! to overcome this when using fixings to fix insulation board alone then tube fixings are used i dont understand why a second layer of plywood is required ? i would lay one layer of ply and then fully adhere the insulation and waterproofing layer edited to add the above applies to single ply, no idea when it comes to fibreglass Edited November 13, 2012 by meinderby Quote Link to comment Share on other sites More sharing options...
Northamptonclay Posted November 14, 2012 Report Share Posted November 14, 2012 try Sikaflex, you can get it from builders merchants, if its a small area it should be ok ...... the reason that you cant use fixings is you will potentially create a cold bridge through the fixing from the outside to the inside, building control dont like these !!!!!! to overcome this when using fixings to fix insulation board alone then tube fixings are used i dont understand why a second layer of plywood is required ? i would lay one layer of ply and then fully adhere the insulation and waterproofing layer edited to add the above applies to single ply, no idea when it comes to fibreglass See post 9 . Already recommended sikaflex Quote Link to comment Share on other sites More sharing options...
al4x Posted November 14, 2012 Report Share Posted November 14, 2012 hi chaps, been doing a roof and it incorporates a flatroof between two pitched roofs, the timber work isn't a problem but the spec says 100mm of cellotex on top of the ply then another skin of ply, then either fiberglass or felt. so what do i stick the insulation stuff down with please? cheers, gram. edit, normally i'd leave all that stuff to guys in the know, but it's a small builder i'm doing the work for and i don't think he knows much about it. go onto the celotex site and you can download the fixing instructions, your BCO needs a talking to if he won't allow mechanical fixings as certainly nowhere does celotex say you can stick it down. There are guidelines to number of fixings based on wind loads etc that you need to comply with. Cold bridging wise bearing in mind you are fixing into timber will be minimal and factored into the specification of thickness you are being asked to fit. Personally I would download and print out the fixing instructions then work out the wind speed part for the area the work is to be done in and call him out again. Then you want it in writing they are telling you not to fix as per the manufacturers specifications and make sure you keep a copy of that and the householder does. Quote Link to comment Share on other sites More sharing options...
The Duke Posted November 14, 2012 Report Share Posted November 14, 2012 Finished an orangery yesterday the flats were only 500 wide so no adhesive required, so unfortunately no suggestions on that note but the edges were 4x2's ply fixed to that then aris rail on top Quote Link to comment Share on other sites More sharing options...
Cosd Posted November 14, 2012 Report Share Posted November 14, 2012 We fitted Celotex on the roof of my friends' "man cave" (big shed), and used long screws through to the joists, 6 screws on each 8x4 sheet was more than enough. Cos Quote Link to comment Share on other sites More sharing options...
Paddy Galore! Posted November 14, 2012 Author Report Share Posted November 14, 2012 hi chaps, thanks for all the suggestions and advice, in the end the boss called the architect just to see what he said, "use long screws!" he replied i guess it really didn't matter afterall , as for wind sheer, there's no worry as the flat roof is basically just a large gulley surrounded on 3 sides by pitched roof. All done now and looking good Quote Link to comment Share on other sites More sharing options...
ME Posted November 14, 2012 Report Share Posted November 14, 2012 You need a Paslode nail gun. You can fix anything to anything with one of those. I have one you can rent (it works by the way :good: ) Quote Link to comment Share on other sites More sharing options...
Paddy Galore! Posted November 14, 2012 Author Report Share Posted November 14, 2012 You need a Paslode nail gun. You can fix anything to anything with one of those. I have one you can rent (it works by the way :good: ) they are rather good aren't they so, have you managed to nail yourself with it yet? Quote Link to comment Share on other sites More sharing options...
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