Cold deck fig 1
This is the most common construction but is also the least thermally efficient.
From the room ceiling up the build is as follows: The roof joists support
the roof construction the internal ceiling is attached to these, between
the joists in the roof void insulation is laid in buildings constructed
in the 60s, 70s, & 80s, there will most likely be some type of insulation
between the rafters in the roof void. On top of the joists the roof deck
is fixed and the waterproof roof cover is laid.
Warm deck fig 2
This is the most modern method of construction and should be used were possible
(although not all situations are able to accommodate this design).
From the room ceiling up the build is as follows: The roof joists support the roof construction the internal ceiling is attached to these. On top of the joists the roof deck is fixed. A vapour barrier is laid on to the deck. And the appropriate thickness of insulation is fixed to the roof deck. The waterproof roof cover is then installed.
This method of insulating the roof alleviates the formation of condensation in the roof void, and complies with the current building regulation.
