Cold Flat Roof Construction Detail

There are three recognised designs of flat roof construction.

Cold flat roof construction detail.

A flat roof must be strong durable and stable throughout its lifetime. It must provide adequate protection against the elements keeping the buildings structure and interior dry. Cold deck roof a cold deck roof is where the insulation is placed between the joists rafters or in between the ceiling joists in the case of a pitch roof. The 3 most common materials used for flat roof construction.

It is usually the most acceptable type of construction for domestic possessions and belongings as it avoids the need for aeration of the roof construction. Hot tar and gravel. There must be an adequate void minimum 50mm between the deck and the insulation traditionally mineral wool to allow free movement of air and to prevent moisture vapour being transmitted from the building outwards where it could condensate in the roof. Flat roof types.

For that reason cold flat roof construction needs to keep in mind the need for unblocked airflow. In the case of a flat roof insulation is usually in the form of either a rigid board above the deck or a fibrous quilt immediately above the ceiling depending on the type of roof construction. In case of warm roofs they have an insulation above the roof deck in this way it keeps the deck warm. There are several methods and materials for the design of the exterior surface of a warm or cold flat roof.

The construction of the flat roof is similar to that of the timber upper floor. No ventilation is required for these types of roofs. The membrane is then attached to the insulation. Warm roof build ups can be installed on most modern construction material types such as concrete timber and timber based sheets.

A warm deck roof is where the insulation is placed on top of the rafters joists and the roof covering is then placed over the insulation. In a cold roof construction the sarnafil membrane is installed directly to the structural decking usually timber with firrings to fall. Trada and approved document part a give guidance on sizes of joists for flat roofs relating to spans and loading. Warm cold and inverted.

A roof is defined in bs 6229 as a flat roof if it has a pitch of 10 degrees or less. Flat roof design guide.