Warm Flat Roof Joist Construction

Getting the balance right here is crucial as too much weight will inevitably lead to an unstable roofing structure.

Warm flat roof joist construction.

The construction of the flat roof is similar to that of the timber upper floor. Or else on the interior of the building just. Yet for historic modern style buildings like this old house s cambridge tv project flat roofs are at the core of the architecture meant to reflect the broad horizontal lines of the natural landscape. Joists are placed on edge spaced at 400 600mm centres supported by external and internal load bearing walls.

The insulation is immediately below the waterproofing layer. Learn more about warm roof cold roof construction. Of course you don t need to live in a modern house to deal with a flat roof. The vapour control layer is above the decking but below the insulation.

On a basic level flat roof construction comes in the form of roofing timbers or joists as they are more commonly known or steels that are laid across two uprights walls in most cases. In the warm flat roof construction there is insulation packed into every possible space where air can flow. Trada and approved document part a give guidance on sizes of joists for flat roofs relating to spans and loading. No ventilation is required for these types of roofs.

A warm flat roof or a built up roof bur is one where all the insulation is above the joists deck making them part of the warm fabric of the building. Flat roof with no permanent access and altitude not exceeding 100m 0 75 kn m udl 0 9 kn point load most areas exceeding 100m but not exceeding 200m excluding parts of scotland pennines north east england refer to bs 6399 3 1 kn m udl 0 9 kn point load. Thermoplastic or elastomeric are the most effective and should extend up adjacent walls at least 150mm from the roof surface. The steels or rsj s rolled steel joists are often built into one or both walls to give added stability to the roof structure.

Flat roofs aren t architecturally logical as rain and snow will shed much more quickly off a sloped roof. 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. A thermal layer of fibreglass polystyrene or other insulating material should be inserted either above the roof decking the warm roof model which is suitable for homes or permanent residences.