Flat Roof Joist Construction Details

There are key differences between constructing a flat roof compared to a pitched roof and it s important to understand the basic criteria.

Flat roof joist construction details.

Sizes of joists needed for flat roof construction. 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. In the warm flat roof construction there is insulation packed into every possible space where air can flow. By way of metal flat roof joist hangers.

Of course you don t need to live in a modern house to deal with a flat roof. I joist construction details. This demo version is fixed at 1m clear span. Flat roofs aren t architecturally logical as rain and snow will shed much more quickly off a sloped roof.

Joists are placed on edge spaced at 400 600mm centres supported by external and internal load bearing walls. Using timber wall plates. What is the process of building a flat roof. In addition to floor and roof framing details this guide includes recommendations for cantilevers and placement of web holes.

Flat roof with asphalt finish with felt boarding insulation. 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 joists in floor and roof applications. 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 starting point involves laying roofing joists across the two upright items which in most cases will be the walls of the structure. 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. Masonry cavity wall flat roof insulation above and between joists.

Good installation begins with specification of the correct joist for the application. 1 enter joist details 1 1 span and joist spacing. Flat roof joist calculator. Apa performance rated i joists pris are manufactured in accordance with pri 400 performance standard for apa ews i joists form x720 this performance standard provides an easy to use table of allowable spans for applications in residential floor construction allowing designers and builders to select and use i joists from various member manufacturers using just one set of span.

The construction of the flat roof is similar to that of the timber upper floor. So any timber joists that are used need to be strong enough to support this weight.