What Timber To Use On A Flat Roof

Installing deck on a flat roof tips.

What timber to use on a flat roof.

The basic construction of a flat roof starts with roofing timber that is laid across two upright items usually two walls. Just enough slope to drain water but also flat enough to be a problem if not constructed properly. Push fit easyfix shoes at gaps of 400mm down the length of timber battens 8 per m2 recommended. C16 timber is commonly used in floor and roof joists for internal building work.

When timbers are used in flat roofing they obviously need to be waterproofed so boards are normally laid across the joists and then a felt or rubber is used to cover the boards to make them waterproof. From the initial building and installation to the materials most often used to cover the roof flat roofs are fairly cheap. In the majority of cases the covering will be plywood or osb timber which is more commonly called stirling board. By far the biggest advantage of using a flat roof is the expense.

For additional stability you can also use steel joists that are built into one or both of the walls. Ensure that the product has been duly certified by the british board of agrément bba before it is used for your project. The usual recommendation is that osb 3 or osb 4 bs en 300 should be used in flat roofs. Osb has almost the same application and usefulness as the plywood it is made from wafers of timber rather than full sheets of veneer.

Of course flat roofs are not flat but have a very slight roof pitch of between 1 4 to 1 2 per foot. Although the construction of the actual roof component of a parapet roof is almost identical to a typical pitched roof it is wise to use a greater minimum roof pitch than is recommended by the roof sheet. 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. Having a manual for warm flat roof construction with details and a summary of rules to follow helps.

It s often chosen as the standard timber for roof extensions or joist refurbishment as it s the most cost effective internal structural timber. 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. Choose what height timber batten to use paying close attention to the height of any existing door threshold. 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.