With a flat roof this issue does not arise but the u value constraint and the amount of insulation needed is just the same.
Warm flat roof insulation depth.
A flat roof where the insulation sits below the waterproof membrane and above the structural deck is a warm roof deck.
This means that the insulation should be highly resistant to water absorption for example an extruded polystyrene based product which will not be affected by water or repeated freeze thaw cycles.
This is placed over the roof joists and a board normally external ply is laid on top.
A cold roof has the insulation placed below the structural deck which thus remains cold.
Cold deck this is where the insulation is placed between the joists rafters or in between the ceiling joists in the case of a pitch roof.
Warm deck the type of insulation for this is usually of a rigid type and the thickness will vary depending on the manufacturer s specifications.
Warm flat roofs do not need to be ventilated as the insulation is.
With solutions ranging from our optim r vacuum insulation panels to our therma range of pir insulation we can provide the best solution for flat roof insulation for roofs with mechanically fixed bonded or torch applied waterproofing systems.
Achieving a u value of 0 20w m meaning your roof will be better insulated than your walls will need 120mm thickness of rigid foam or 200mm of mineral wool or natural insulation.
It should be of the maximum available thickness.
Although i m sure this can differ considerably depending on insulation etc can anyone tell me what the approximate thickness of a warm deck flat roof will be including joists.
There are two basic categories of roof design.
A warm roof has the insulation above the structural deck which is thus kept warm.
Depending on the type and thickness of insulation used warm moist air will be controlled accordingly.
Cold flat roofs are typically avoided as you d need to install ventilation which can prove problematic for many reasons relating to space labour costs etc.
The chosen insulation laid on top of this should be able to take the weight of anything put above it on the roof without compression or protected from compression by further sheeting.
The typical u value of an existing uninsulated flat roof is 1 5w m2k.
The waterproof layer is above the insulation and a vapour control layer is placed below the insulation.
Reason i ask is because i m trying to work out whether my upstairs toilet waste pipe will be high enough to divert on top of the flat roof to the side of the house.
Our range of high and optimum performance flat roof insulation products are suitable for use in a range of flat roofs.
In the case of a flat roof insulation is usually either a rigid board above the deck or a mineral glass wool quilt immediately above the underdrawn ceiling depending on the type of roof design and construction.
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.
Ventilation is required for these roofs.
