Flat Roof Fixing

[hankmarvin]

Hi there,

Is there a best brand/cheapest/quality go to flat roof fixing?

My requirement is for a warm flat roof

18mm deck
110mm insulation
25mm to 125mm firring
joists

45sqm total area.

Can the fixings go 35mm into the firring which has been nailed to the joist or do they have to go 35mm into the joist? This will really effect how long the fixings need to be.

Also whats a standard amount of fixings per sheet?


Thanks very much in adavance.

 

[hankmarvin]

Anyone got any thoughts?

Cheers

 

[nickjb]

You seem to have your deck outside the insulation. For it to be warm then shouldn't it be under the insulation.

E.g.:

 

[hankmarvin]

Still a warm roof, I'm just omitting osb below the insulation. 400mm centres and 110mm insulation and I'll support edges that don't finish on a joist (75mm)

Just really need to know if the fixings can just go into the firrings in places and not the joist. Firrings will be nailed to joists.

 

[^woody^]

Yes you can fix into the furrings as long as they are themselves secure to the joists.

I would not fit insulation direct to joists without a layer of boarding. They will settle and compress on the joists, even as you are working on them and finishing the roof, causing dips. Also, as the deck moves naturally, they wear on the joists too, dipping and causing nails/screws to pop the deck covering.

I think fixings are every 200-300mm around edges and along joists, but can't recall if that's the recommended number or not or if it can be less.

 

[hankmarvin]

Hmmmm I wouldn't want any dips leading to pooling. Ok I'll use the 18mm as deck (vapour layer below it) and 9mm over insulation.

That's going to be a lot of fixings then, better get a 400 pack.

170mm fixings will give me about 43mm depth into wood, ok or go for 195mm fixings?

and is this stuff http://www.ebay.co.uk/itm/Roof-Vapo...336?pt=LH_DefaultDomain_3&hash=item3a80017138 ok for VCL? Saw it mentioned on here somewhere. But I guess something wider like dpm material below pad would be easier, less joins to tape.


Cheers all

 

[hankmarvin]

http://www.insulationexpress.co.uk/Accessories/BIG-TWIST-Fixings.htm These are in the pitched roof section but i'm sure they are what I need and about £60 cheaper than I've found elsewhere........agree?

 

[^woody^]

Yes those will do. But see if you can find out the recommended spacing though so that you don't spend more than you need to

 

[hankmarvin]

Seems to be 8.6 fixings p/m2, 400mm spacing along the joist, that's for 400mm centred joists.

http://surecps-group.com/wp-content/uploads/2013/pdf/big_twist.pdf handy guide.