The waterproof layer is above the insulation and a vapour control layer is placed below the insulation.
Warm deck flat roof insulation thickness.
Warm deck flat roofs can be constructed on most modern construction material types such as concrete timber and timber based sheets.
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.
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 joist size depends on your span but assuming you are going out say 3m or so your joists would be about 150 deep.
A cold roof has the insulation placed below the structural deck which thus remains cold.
18 thickness of deck.
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.
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.
Add to this the firring pieces for slope say 75 max.
When building a flat roof it is vital that a degree of falls is built into the construction to ensure rainwater run off.
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.
The required thickness of quinn therm flat roof insulation will depend on the desired u values.
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.
They lose loads of heat and are prone to leaking causing the materials to deteriorate.
The below u value table shows the required insulation thickness based on the typical warm flat roof construction outlined.
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.
To calculate u values and insulation thickness specific to your project use our free online u value calculator.
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.
Warm flat roofs do not need to be ventilated as the insulation is.
