Flat Roof Joist Construction Details

Masonry cavity wall flat roof insulation above and between joists.

Flat roof joist construction details.

Flat roofs aren t architecturally logical as rain and snow will shed much more quickly off a sloped roof. There are key differences between constructing a flat roof compared to a pitched roof and it s important to understand the basic criteria. Good installation begins with specification of the correct joist for the application. The starting point involves laying roofing joists across the two upright items which in most cases will be the walls of the structure.

This demo version is fixed at 1m clear span. Of course you don t need to live in a modern house to deal with a flat roof. The full version allows any size. Using timber wall plates.

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 roof with asphalt finish with felt boarding insulation. 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. By way of metal flat roof joist hangers.

So any timber joists that are used need to be strong enough to support this weight. I joists in floor and roof applications. 1 enter joist details 1 1 span and joist spacing. Flat roof detail masonry cavity wall flat roof insulation above and between.

In the warm flat roof construction there is insulation packed into every possible space where air can flow. The construction of the flat roof is similar to that of the timber upper floor. 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 calculator.

Joists are placed on edge spaced at 400 600mm centres supported by external and internal load bearing walls. Sizes of joists needed for flat roof construction. What is the process of building a flat roof. I joist construction details.

In addition to floor and roof framing details this guide includes recommendations for cantilevers and placement of web holes. 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.