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.
How to build a cold flat roof.
In a cold weather such roofs are inherently prone to condensation which can cause material decay and deterioration.
Consider geography budget and use for the roof to determine the best option.
A note to consider before construction.
This arrangement allows the deck to become cold.
For both a warm and cold flat roof a vapour control layer must be installed.
These roofs are mostly flat but usually have a bit of a slope.
Building regulations state that a ventilation gap of at least 50mm must be in place between the insulation and the underside of the flat roof deck.
The 3 most common materials used for flat roof construction.
Flat roof construction can come in the form of a warm roof or cold roof depending on the requirement of the owner and architect as they relate to the building regulations regarding heat loss and insulation.
As such they allow for outdoor living gardens or a living space on top.
If insulation is installed below the flat roof deck this is called a cold roof.
As the name suggests a pyramid roof is a roof in the shape of a pyramid and is designed for a square building.
There are several methods and materials for the design of the exterior surface of a warm or cold flat roof.
From there the flat roof system you choose will determine the materials you apply.
In the case of cold roofs the residential flat roofs have the waterproof placed directly on the deck and any insulation would be placed above the ceiling.
Types of flat roof construction warm and cold flat roofs.