Cold Flat Roof Ventilation Building Regulations

Cold deck flat roof the thickness of insulation required will vary depending on the material you decide to use and the manufacturer s specification.

Cold flat roof ventilation building regulations.

Warm deck this is where the insulation is placed on top of the rafters joists and the roof covering is then placed over the insulation. Roof voids must be ventilated in order to stop warm air condensing on cold surfaces. Cold roof voids are generally always required to be ventilated. The air gap dimensions shown on the drawings are the minimum widths required for clear continuous ventilation air paths at the eaves.

There must be a slope of 1 80 part h of the building regulations regarding drainage state that water should drain to one or two edges waterproofing should extend up the adjacent walls at least. Ventilation is required above the insulation in a cold roof to prevent the build up of moisture vapour in the roof void. For both a warm and cold flat roof a vapour control layer must be installed. Cold deck this is where the insulation is placed between the joists rafters or in between the ceiling joists in the case of a pitch roof.

Ventilation is not required to a warm roof system which is where the insulation is placed above the joists or rafters. Ventilation at the eaves. A ventilation gap usually 50mm should be. Because the structural elements of a cold roof are not protected by from the heat of the sun by a layer of insulation they are liable to suffer the damaging effects of thermal movement.

No ventilation is required for these types of roofs. Building regulations state that a ventilation gap of at least 50mm must be in place between the insulation and the underside of the flat roof deck. Duo pitch roofs greater than 200 pitch or greater than 10m span should have additional ventilation at the ridge to assist airflow through the roof void equivalent to at least a 3 mm wide continuous gap. A qualified roofing contractor will be able to advise on this but here are some of the main guidelines.

When ventilating a roof the air should be able to enter at one end and travel through to the other end where it can exit. Not all roofs need to be ventilated. Ventilation is required for these roofs.