Flat Roof Joist Construction

The construction of the flat roof is similar to that of the timber upper floor.

Flat roof joist construction. Many slope in several directions like squashed hip roofs toward scupper holes that connect to downspouts. Flat roofs with a slight slope can be achieved using trus joist tji joists and solid section products. The standard construction of interior framing in a home uses 16 inch on center oc spacing for ceiling joists. Joists are placed on edge spaced at 400 600mm centres supported by external and internal load bearing walls.

Maximum clear span of flat roof joists in metres for sc3 timber spacing between joists size of roof joist 400mm 450mm 600mm 47 x 97 1 84 1 81 1 74 47 x 120 2 43 2 39 2 27 47 x 145 3 08 3 02 2 87 47 x 170 3 75 3 67 3 42. Flat roof joist calculator. Trada and approved document part a give guidance on sizes of joists for flat roofs relating to spans and loading. On a basic level flat roof construction comes in the form of roofing timbers or joists as they are more commonly known or steels that are laid across two uprights walls in most cases.

Joist spacing in this design mode incorporates different types of wood used in ceiling construction including 2 grades of southern pine douglas fir and hemlock fir types which are the most common. Getting the balance right here is crucial as too much weight will inevitably lead to an unstable roofing structure. The steels or rsj s rolled steel joists are often built into one or both walls to give added stability to the roof structure. The basic construction of a flat roof starts with roofing timber that is laid across two upright items usually two walls.

The most important thing to know about a flat roof says tom is that it s not flat to prevent water from pooling and eventually invading the home flat roofs are always built on a slight incline at least 1 8 inch per foot. Flat roofing under construction plywood decking is then used to cover the joists with the width in between also determined by the weight being placed upon them. 1 enter joist details 1 1 span and joist spacing. It is the responsibility of the designer of record to address items like ponding snow drift loads lateral loads wind loads bracing ventilation and insulation when adding a slope to roofs.

Ceilings and roofs excluding trussed rafter roofs for dwellings or ask your lbc surveyor for advice. This will give additional stability to the roof structure. Suitable for uk building regulation approval.