Cold roof insulation advice after problems originally

[sean oc]

Afternoon

Some of you remember the nightmare i had with a roofing firm, building a wonky brick pier, using 3x2 on 2.8m span and fitting windows that didn't fit, they also had fitted the osb boards and glued down the rubber roof - see thread below - finally got some cash back and was left with a disaster to try and fix it up to a safe reasonable standard

See thread here
https://www.diynot.com/diy/threads/...ew-flat-rubber-roof-please-pics-added.549525/

So got someone else in to try and fix the issue, so they have worked round what was there rather than rip off and ruin the one piece rubber and boards etc.

So new brick piers fitted, 6x2 used and a proper frame all the way round. as new pics added so the 3x2 are still present due to hassle of being ripped up/out

my question is over cold flat roof insulation as its going to be hard to insulate over 2 sets of joists, i was thinking of using kingspan 75mm in-between joists so still gives me 50mm air gap above for ventilation, then using some insulated pasteboard under rafters to try and get as much insulation depth as we can.

Any advice would be ideal, thanks

 

[Mr Chibs]

I remember reading your post, glad you’ve got it sorted.

Only thing with your method, is there is no opportunity for any damp air to vent.
Others will comment, but would think you need some vents putting in the fascia boards.

ps, separate insulation boards and plasterboard are cheaper as separates.