Thickness Of Insulation For Warm Flat Roof

These are can be supplied with rebated edges which interlock reducing the risk of uplift.

Thickness of insulation for warm flat roof. This is placed over the roof joists and a board normally external ply is laid on top. At least 100mm of rigid board insulation must be positioned on top of the vapour control layer the vapour control layer stops any moisture within the building. Insulation in a warm roof. With a flat roof this issue does not arise but the u value constraint and the amount of insulation needed is just the same.

Flat roof u value 0 18 w m2k 2 warm deck flat roof the type of insulation for this is usually of a rigid type and the thickness will vary depending on the manufacturer s specifications. The typical u value of an existing uninsulated flat roof is 1 5w m2k. One of the main benefits you will receive from installing a warm flat roof is condensation will not become an issue because of the positioning of the insulation. Although i m sure this can differ considerably depending on insulation etc can anyone tell me what the approximate thickness of a warm deck flat roof will be including joists.

Reason i ask is because i m trying to work out whether my upstairs toilet waste pipe will be high enough to divert on top of the flat roof to the side of the house. Ventilation is required for these roofs. It should be of the maximum available thickness. 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.

The chosen insulation laid on top of this should be able to take the weight of anything put above it on the roof without compression or protected from compression by further sheeting. Warm flat roofs do not need to be ventilated as the insulation is. The insulation for a warm roof will usually be boards of extruded polystyrene or rigid compressed boards of glass fibre or rock fibre. However if we do not include removal of old roofing you are looking at about 7 50 to 9 00 per foot of roofing plus about 2 50 to 3 00 per foot of 5 thick insulation say about 10 12 per square foot.

A flat roof where the insulation sits below the waterproof membrane and above the structural deck is a warm roof deck. Warm deck the type of insulation for this is usually of a rigid type and the thickness will vary depending on the manufacturer s specifications. Inverted roofs are a type of warm flat roof where the insulation is above the waterproofing layer. Achieving a u value of 0 20w m meaning your roof will be better insulated than your walls will need 120mm thickness of rigid foam or 200mm of mineral wool or natural insulation.

Cold flat roofs are typically avoided as you d need to install ventilation which can prove problematic for many reasons relating to space labour costs etc. The insulation material for a warm flat roof should.