Flat Roof Joist Layout

Where a new flat roof abuts an existing external wall the joists can be hung on metal joist hangers which are fixed to a horizontal timber plate wall bolted to the wall.

Flat roof joist layout.

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. A flat roof usually consists of the following. Flat roof joist layout. We ripped off the old flat roof wow did this really need to happen added a third level and are now getting ready to build the roof to it see your thoughts on our joist layout and the materials we are considering to use are greatly appreciated.

As you may imagine there is a fair amount of weight involved here in terms of boards felt etc. Flat roof construction for residential. Joists are the repeated structural members that are used to build a deck. Floor beam span tables of residential structural design we will now look at roof rafter and beam design.

Similarly ceiling joists are the planks of wood that create the flat surface of your attic floor or top story ceiling. Ceiling joists can be on both low sloped roofs and high sloped roofs and help to prevent racking and spreading of your rafters or walls which could lead to sagging. Let s consider a basic gable wood roof framing design. Old asbestos roofs are often replaced with flat roofs.

Waterproof membrane to prevent water penetrating the structure and interior of the. So any timber joists that are used need to be strong enough to support this weight. Flat roof with no permanent access and altitude not exceeding 100m 0 75 kn m udl 0 9 kn point load most areas exceeding 100m but not exceeding 200m excluding parts of scotland pennines north east england refer to bs 6399 3 1 kn m udl 0 9 kn point load. A roof is considered to be flat when it is of a slope of 1 5 o to the horizontal.

Although flat roofs are cheaper to build than pitched roofs they have a shorter life span. They are important load bearing structural elements. Roof rafter span use this table to determine the maximum lengths of roof rafters based on species and grade of lumber spacing dimensions load and slope. A cavity closer should be provided to the top of the walls to prevent fire spread and to stop damp air entering the roof space.

Sizes of joists needed for flat roof construction. The image below shows a cross section of our simple 12 x 13 house from the joist span tables section of this tutorial. Here we have a wood framed gable roof.