Flat Roof Joist Construction Details

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.

Flat roof joist construction details.

Flat roof joist calculator. The starting point involves laying roofing joists across the two upright items which in most cases will be the walls of the structure. The full version allows any size. Flat roofs aren t architecturally logical as rain and snow will shed much more quickly off a sloped roof.

Of course you don t need to live in a modern house to deal with a flat roof. The construction of the flat roof is similar to that of the timber upper floor. As you may imagine there is a fair amount of weight involved here in terms of boards felt etc. In the warm flat roof construction there is insulation packed into every possible space where air can flow.

I joists in floor and roof applications. This demo version is fixed at 1m clear span. There are key differences between constructing a flat roof compared to a pitched roof and it s important to understand the basic criteria. Masonry cavity wall flat roof insulation above and between joists.

When building a flat roof it is vital that a degree of falls is built into the construction to ensure rainwater run off. So any timber joists that are used need to be strong enough to support this weight. By way of metal flat roof joist hangers. 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. Flat roof detail masonry cavity wall flat roof insulation above and between. What is the process of building a flat roof. Others would treat even steeper pitches as flat roofs.

Important note for cold roof construction a 50mm airspace is required for ventilation purposes over the insulation the minimum depth of joist required is usually taken as 175mm even if a lesser depth would be acceptable from a purely structural point of view ventilation details for flat roofs. In addition to floor and roof framing details this guide includes recommendations for cantilevers and placement of web holes. This article covers all manner of flat roofing venting methods and details on how to build a flat garage roof and how to frame a flat roof and also encompasses flat roofs roof decking roof coverings including flat roof felt how to prevent leaks at abutments timber flat roof construction details and parapets and common. I joist construction details.

Old asbestos roofs are often replaced with flat roofs. Using timber wall plates. The definition of a flat roof according to bs 6229 is having a pitch less than 10 o to the horizontal however some in the industry would consider up to 15 o as their definition of a flat roof. 1 enter joist details 1 1 span and joist spacing.