Warm Flat Roof Construction Details Building Regulations

There must be a slope of 1 80.

Warm flat roof construction details building regulations.

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. No ventilation is required for these types of roofs. Warm roofs must have a vcl bonded to the deck. It must provide adequate protection against the elements keeping the buildings structure and interior dry.

Flat roofs are hard to replace. With this type of roof the insulation is placed above the roof deck but below the weatherproofing. Warm deck sandwich or cold deck. Having a manual for warm flat roof construction with details and a summary of rules to follow helps.

Steve from london flat roofingexplains how warm flat roof construction works in this excellent short video. Trada and approved document part a give guidance on sizes of joists for flat roofs relating to spans and loading. A warm flat roof is formed by placing a layer of insulation over the top of the roof structure. But now flat roofs often are constructed with fewer layers because of improved waterproofing technology.

Warm deck this is where the insulation is placed on top of the rafters joists and the roof covering is then placed over the insulation. There are two common forms of construction for flat roofs. Some observers suggest it s harder to replace a flat roof than a traditional pitched shingle roof because of the labor required to remove its layers especially on older flat roofs. Cold roofs must have ventilation.

The construction of the flat roof is similar to that of the timber upper floor. Joists are placed on edge spaced at 400 600mm centres supported by external and internal load bearing walls. Warm flat roof fully packed with insulation to prevent any condensation build up. 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 should be no insulation below the deck and no ventilation is required. A flat roof must be strong durable and stable throughout its lifetime. This could mean flat roofs may not raise the same red flags they used to. A roof is defined in bs 6229 as a flat roof if it has a pitch of 10 degrees or less.

For additional stability you can also use steel joists that are built into one or both of the walls. Due to the insulation being over the top of the roof the timber structure beneath is warm which is why the term warm roof is formed. The basic construction of a flat roof starts with roofing timber that is laid across two upright items usually two walls.