Warm Roof Versus Cold Roof: What Does It Mean?
A warm roof keeps the structural deck on the warm side of insulation. A cold roof places insulation below the deck and normally needs a ventilated void.
A warm roof keeps the structural deck on the warm side of insulation. A cold roof places insulation below the deck and normally needs a ventilated void.
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Warm-roof build-up
Insulation above the deck reduces the chance that the deck becomes a cold condensation surface. Edges and upstands may need raising.
Cold-roof build-up
Insulation sits between or below joists, with a ventilation path above. Achieving reliable airflow can be difficult on some existing roofs.
Why moisture control matters
Warm indoor air can carry moisture into colder layers. Vapour control, airtightness and ventilation should be designed as part of the roof.
What to ask before replacement
Ask for a drawing or plain description of each layer, how edges change and what current standards apply to the work.
Questions about this topic
Can roof photographs answer every question about warm and cold roofs?
No. Clear photographs help, but hidden underlay, fixings, deck and water routes may still need close inspection.
Should I inspect warm and cold roofs by climbing onto the roof?
No. Roof work is dangerous even when the check seems quick. Photograph warm and cold roofs from ground level or a safe window and leave close access to trained people with the right equipment.
When should I request a written quote for warm and cold roofs?
Ask for a written quote after warm and cold roofs and the access needs have been assessed. It should set out the work, materials, exclusions and any likely extras.