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.

Flat roof joist layout.

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. Waterproof membrane to prevent water penetrating the structure and interior of the. 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.

Flat roof joist layout. Although flat roofs are cheaper to build than pitched roofs they have a shorter life span. Here we have a wood framed gable roof. A flat roof usually consists of the following.

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. Let s consider a basic gable wood roof framing design. Flat roof construction for residential. Joists are the repeated structural members that are used to build a deck.

Similarly ceiling joists are the planks of wood that create the flat surface of your attic floor or top story ceiling. Floor beam span tables of residential structural design we will now look at roof rafter and beam design. Old asbestos roofs are often replaced with flat roofs. They are important load bearing structural elements.

So any timber joists that are used need to be strong enough to support this weight. Floor joist span use this table to determine the maximum lengths of floor joists based on species of lumber joist spacing and joist size. A roof is considered to be flat when it is of a slope of 1 5 o to the horizontal. 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.

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. 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.