Warm Deck 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 deck flat roof insulation thickness.

18 thickness of deck. Saint gobain insulation uk manufacture and supply glass mineral wool slabs and rolls along with rigid polyisocyanurate pir boards that can be considered suitable for a wide range of applications across flat roofs whether you re looking to insulate at joist level or above the roof deck in your flat roof construction. Others would treat even steeper pitches as flat roofs. Ventilation is required for these roofs.

Min 125 thickness of insulation board then finish on top. A warm roof has the insulation above the structural deck which is thus kept warm. The below u value table shows the required insulation thickness based on the typical warm flat roof construction outlined. When building a flat roof it is vital that a degree of falls is built into the construction to ensure rainwater run off.

The joist size depends on your span but assuming you are going out say 3m or so your joists would be about 150 deep. The definition of a flat roof according to bs 6229 is having a pitch less than 10 o to the horizontal however some in the industry would consider up to 15 o as their definition of a flat roof. To calculate u values and insulation thickness specific to your project use our free online u value calculator. 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.

Add to this the firring pieces for slope say 75 max. 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. Warm deck flat roofs can be constructed on most modern construction material types such as concrete timber and timber based sheets. Warm flat roofs do not need to be ventilated as the insulation is.

Cncd 053 v1 5 7 2019 0 cold deck flat roof the thickness of insulation required will vary depending on the material you decide to use and the manufacturer s specification. To use epdm for a warm deck flat roof construction solid closed cell roof insulation such as kingspan or celotex should be placed on top of the roof deck rather than in between the rafters. A cold roof has the insulation placed below the structural deck which thus remains cold. There are two basic categories of roof design.

Warm deck flat roof insulation is now the standard way to insulate a flat roof click to enlarge flat roofs for example on extensions bathrooms and dormer windows are not the best of ideas. 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.