This approach uses insulation with no air gap either immediately above or below the roof deck.
Flat roofing warm flat roof fascia detail.
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.
Underneath the basics flat roofs are usually constructed with a ceiling nailed to joists which support a deck usually wood in residential construction a vapor barrier insulation and a roof board.
Flat roofing is a popular choice for garages homes garages extensions and many other types of buildings.
A timber decking is then constructed and its weight supported by the joists.
Cad details document name pdf dwg download all cad construction details 37 1 mb 3 4 mb mc01 identification of roof areas 694 kb 167 kb mc01a single layer underlayment 678 kb 302 kb mc01b double layer underlayment 711 kb 322 kb mc02 vent pipe flashing 626 kb 349 kb mc03 valley.
From there the flat roof system you choose will determine the materials you apply.
Having a manual for warm flat roof construction with details and a summary of rules to follow helps.
Traditionally domestic flat roofs use two or more built up layers of bituminous felt as their weather proofing.
Whatever new flat roof covering you choose epdm rubber kemper liquid rubber triflex mariseal etc.
In this video our principal surveyor steven dickinson explains problems with insulating a roof using the warm and cold roof construction methods.
A warm flat roof is formed by placing a layer of insulation over the top of the roof structure.
Flat roof joists spanning the shorter length of the roof form the load bearing members of the structure.
If the specification of the insulation is not correct you could have problems.
The roofs have a timber frame as the supporting structure.
Good question theoretically when building a warm roof the vaper control layer goes on the warm side of the insulation.
Single ply membranes are also used but are particularly suitable for larger roofs.
If you put insulation under the decking and between the joists you lower the temperature of the decking and lower the due point thus bringing it closer to the danger point of being in the building.
Front fascia flat roof detail.
A 50mm air gap must be left above the insulation and allowance for venting must be made at roof perimeters.
A vapour control layer must be used below the insulation.
This option avoids the requirement to ventilate the roof.
This is where the insulation is typically packed between the rafters.
Liquid applied systems such as glass fibre were introduced and are now quite widely used.