Warm Flat Roof Build Up

Warm flat roof fully packed with insulation to prevent any condensation build up.

Warm flat roof build up.

4 essentials for a successful flat roof like any part of a building s exterior flat roofs should be constructed to withstand natural and human forces with the minimum of attention. A thermal layer of fibreglass polystyrene or other insulating material should be inserted either above the roof decking the warm roof model which is suitable for homes or permanent residences. If you have an existing cold roof in need of refurbishment it should be converted to a warm roof see sketch 1 to meet part l of the building regulations. Flat roof constructions are generally classed as either cold or warm.

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. Flat roofs have a reputation of failing early but improvements in strength flexibility ageing and weather resistance mean that if built with care using the correct materials today s high performance felts can have a life span of up to 20 years. Warm cold and inverted. In a warm roof construction the principal thermal insulation layer is located above the structural decking resulting in the structural deck and support structure being at a temperature close to that of the interior of the building.

Others would treat even steeper pitches as flat roofs. In a warm roof the thermal insulation is immediately below the membrane finish the structural deck any voids and the ceiling are at a temperature close to that of the building s interior condensation control is achieved by using a vapour control layer vcl on the warm side of the insulation. Thermoplastic or elastomeric are the most effective and should extend up adjacent walls at least 150mm from the roof surface. The major difference between the warm flat roof and the cold flat roof has to do with the air flow between the roofing timbers known as joists that help to hold up the roof.

Where insulation above the roof void allows the air underneath to stay warm avoiding condensation but also allows for an air flow should one be deemed to be required through the joists. There are three recognised designs of flat roof construction. They can be built up from profiled metal decks as the insulation selected would provide enough rigidity to span the open sections of such decks. Warm roof build ups can be installed on most modern construction material types such as concrete timber and timber based sheets.