Warm Flat Roof Insulation Thickness

A flat roof where the insulation sits below the waterproof membrane and above the structural deck is a warm roof deck.

Warm flat roof insulation 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. Flat roof insulation thickness. 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. The insulation for a warm roof will usually be boards of extruded polystyrene or rigid compressed boards of glass fibre or rock fibre.

Warm flat roofs do not need to be ventilated as the insulation is. This is placed over the roof joists and a board normally external ply is laid on top. A cold roof has the insulation placed below the structural deck which thus remains cold. The insulation material for a warm flat roof should.

There are two basic categories of roof design. 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. Inverted roofs are a type of warm flat roof where the insulation is above the waterproofing layer. Ventilation is required for these roofs.

There are two types of flat roof. The waterproof layer is above the insulation and a vapour control layer is placed below the insulation. A warm roof has the insulation above the structural deck which is thus kept warm. These are can be supplied with rebated edges which interlock reducing the risk of uplift.

In this case ventilation is required and the roof can still become wet with condensation which may cause materials to decay. The typical u value of an existing uninsulated flat roof is 1 5w m2k. 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. Thickness varies according to the manufacturer s specifications.

Cold roofs have the waterproof layer placed directly onto the roof deck and the insulation inside the roof just above the ceiling. 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. 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. With a flat roof this issue does not arise but the u value constraint and the amount of insulation needed is just the same.

It should be of the maximum available thickness. Cold roofs and warm roofs.