Flat Roof Joist Construction Details

I joist construction details.

Flat roof joist construction details.

Flat roofs aren t architecturally logical as rain and snow will shed much more quickly off a sloped roof. Others would treat even steeper pitches as flat roofs. 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. As you may imagine there is a fair amount of weight involved here in terms of boards felt etc.

So any timber joists that are used need to be strong enough to support this weight. Using timber wall plates. 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. Sizes of joists needed for flat roof construction.

Flat roof with asphalt finish with felt boarding insulation. By way of metal flat roof joist hangers. This demo version is fixed at 1m clear span. In addition to floor and roof framing details this guide includes recommendations for cantilevers and placement of web holes.

Good installation begins with specification of the correct joist for the application. 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. 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.

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. The full version allows any size. Of course you don t need to live in a modern house to deal with a flat roof.

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. What is the process of building a flat roof. The construction of the flat roof is similar to that of the timber upper floor. 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. I joists in floor and roof applications. When building a flat roof it is vital that a degree of falls is built into the construction to ensure rainwater run off. The starting point involves laying roofing joists across the two upright items which in most cases will be the walls of the structure.