Room-in-the-roof

It’s unlikely there will be any insulation around older roof rooms, but for more recent conversions, ask a specialist to check whether there’s already enough insulation — ideally 270mm (11”) thick.

If you need to insulate around a room in the roof, call in an expert — this isn’t a DIY job. They would remove the boards that line the room to fit quilt or rigid insulation between the studs and rafters, making sure there’s an air gap at least a 50mm (2”) between the insulation and the roof covering. They may need to add roof vents if there’s a waterproof layer under the tiles or slates.

If you’re replacing the tiles or slates, sarking insulation can be fitted over the rafters.

Flat roof

When you have the covering of a flat roof replaced, ask the roofing contractor whether they can fit rigid insulation fitted over the boards and under the new weatherproof layer — they’ll also need to alter the fascia boards and gutters at the edge of the roof because the layer of insulation will alter the thickness of the roof.

If a roof is closer than 6m to a neighbouring building, it must be flame resistant.

If you add a dormer window, ensure the sides and roof are well insulated.

It can be difficult to insulate around an existing dormer window. Try to line the sides and roof with rigid insulation — and close it off with heavy curtains at night.