Warm Flat Roof Joist Construction

Trada and approved document part a give guidance on sizes of joists for flat roofs relating to spans and loading.

Warm flat roof joist construction.

Thermoplastic or elastomeric are the most effective and should extend up adjacent walls at least 150mm from the roof surface. 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. The major difference between the warm flat roof and the cold flat roof has to do with the air flow between the roofing timbers known as joists that help to hold up the 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.

Constructing a warm roof on a new extension with parapet walls i will have surplus amounts of insulation left over and am considering adding this insulation to the underside between the joists to double up the insulation would this install have any negatives. Getting the balance right here is crucial as too much weight will inevitably lead to an unstable roofing structure. Of course you don t need to live in a modern house to deal with a flat roof. The insulation is immediately below the waterproofing layer.

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. The steels or rsj s rolled steel joists are often built into one or both walls to give added stability to the roof structure. In the warm flat roof construction there is insulation packed into every possible space where air can flow. Learn more about warm roof cold roof construction.

Or else on the interior of the building just. No ventilation is required for these types of roofs. 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. 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.

Flat roofing under construction plywood decking is then used to cover the joists with the width in between also determined by the weight being placed upon them. The construction of the flat roof is similar to that of the timber upper floor. Flat roofs aren t architecturally logical as rain and snow will shed much more quickly off a sloped roof.