DIY Doctor

Warm Deck Flat Roof and Plastic Tube Fixings

Postby netmonkey » Mon Dec 30, 2019 1:10 pm

The roof construction on our new extension will consist of:

Upper Deck (18mm Ply)
120mm Kingspan
Vapour Barrier (resitrix alutrix 600)
Sub/Lower Deck (18mm Ply)
Joists
Plasterboard

We were going to these plastic tube fixings, rather than just metal fixings, to prevent thermal bridging:

https://www.fixfast.com/products/fasten ... ner-system

The tube fixings would be applied to the to upper deck which is 18mm ply. Obviously we would have to drill a hole in the upper deck ply for each fixing.

I'm wondering if we can use these plastic tube fixes if we are using torch on felt for the final roof covering. Is there a way to protect them from melting under the heat? Will they be fine just as they are or is there something we could cover them with to protect them whilst the felt is being applied?

One other concern is the gap these tube fixes leave within the insulation once inserted and screwed down. Should we fill that gap with something to prevent condensation building up, if so, what can we use for that?

If I use metal fixings that won't leave any gap, is thermall bridging something to worry about, especially if the fixes are only applied to the joists and not the lower/sub deck?

Thanks
netmonkey
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