Is this warm roof?

11 Jul 2018
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United Kingdom

The existing flat roof which was build in 2001 has got plan (attached) saying "warm deck flat roof". Does it mean its warm roof (which has insulation on top now a days)?

When looking from inside through a hole in plasterboard its got thermocol insulation boards (very thin).

The plan is ...
Ply on top of joist
1) vapour barrier
2) Insulationboard
3) OSB boards
4) EPDM rubber

The reason is that I need to know if I need to raise height or not for installing new warm roof (if its not already a warm roof).


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the spec says: 75mm purldeck insulation board

so yes it is a warm roof -although not compliant to current regs
I guess thats good news for me. Do I then need to raise the existing facias in order to get the new insulation boards which complies with current BR rules? I am thinking 50 mm more?
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Upon closer inspection (by putting hole from cieling) it turns out its cold roof construction where thermocol sheets are placed between joists. So I guess thats not so great news as the height will increase when converting to warm roof.

Now we know this I have following questions and would be greatful if someone can put some light on this.

I) To convert this into warm roof the height will need to go up meaning,
Ply on top of joist
1) Ply 20mm
2) vapour barrier (2mm - guess)
3) Insulationboard (100mm or 120mm - to comply with BR?)
4) OSB boards (20mm)
5) EPDM rubber (1.5mm)

~ 145-165mm

Is this going to be issue wrt to PP? i.e. now will I need PP as the height now is going to be > then 150mm of original roof?

II) Currently The joist are running at 90 degree to the fall of the roof. I would like to maintain this slope. How does the furring works on the joist which are 90 degree of the slope? (I would have thought it fits inline with the joist?)


PS Really annoyed that the construction is not as stated per the drawings.

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