Flat Roof Joist Construction Details

I joist construction details.

Flat roof joist construction details.

Flat roof detail masonry cavity wall flat roof insulation above and between. This demo version is fixed at 1m clear span. 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. So any timber joists that are used need to be strong enough to support this weight.

Sizes of joists needed for flat roof construction. As you may imagine there is a fair amount of weight involved here in terms of boards felt etc. The starting point involves laying roofing joists across the two upright items which in most cases will be the walls of the structure. Masonry cavity wall flat roof insulation above and between joists.

Old asbestos roofs are often replaced with flat roofs. 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. By way of metal flat roof joist hangers. Flat roof with asphalt finish with felt boarding insulation.

The construction of the flat roof is similar to that of the timber upper floor. 1 enter joist details 1 1 span and joist spacing. Others would treat even steeper pitches as flat roofs. Using timber wall plates.

Good installation begins with specification of the correct joist for the application. 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. 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. In the warm flat roof construction there is insulation packed into every possible space where air can flow.

There are key differences between constructing a flat roof compared to a pitched roof and it s important to understand the basic criteria. Joists are placed on edge spaced at 400 600mm centres supported by external and internal load bearing walls. Flat roof joist calculator. In addition to floor and roof framing details this guide includes recommendations for cantilevers and placement of web holes.

Flat roofs aren t architecturally logical as rain and snow will shed much more quickly off a sloped roof. 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. I joists in floor and roof applications. Of course you don t need to live in a modern house to deal with a flat roof.