Flat Roof Joist Construction

Flat roof joist calculator.

Flat roof joist construction. Of course you don t need to live in a modern house to deal with a flat roof. 1 enter joist details 1 1 span and joist spacing. Ceilings and roofs excluding trussed rafter roofs for dwellings or ask your lbc surveyor for advice. If you have a low sloped roof or flat roof of less than 2 in 12 these evenly spaced planks will be called roofing joists.

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. 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. What is the process of building a flat roof. 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.

There are key differences between constructing a flat roof compared to a pitched roof and it s important to understand the basic criteria. Joist is a term used in construction for load bearing planks that run horizontally or nearly to horizontally to ground. The construction of the flat roof is similar to that of the timber upper floor. Rolled steel joists or rsj s are used to support joists in flat roofs.

Flat roof joists. 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. The basic construction of a flat roof starts with roofing timber that is laid across two upright items usually two walls. Joists are placed on edge spaced at 400 600mm centres supported by external and internal load bearing walls.

Flat roofs with a slight slope can be achieved using trus joist tji joists and solid section products. Flat roofs aren t architecturally logical as rain and snow will shed much more quickly off a sloped roof. Trada and approved document part a give guidance on sizes of joists for flat roofs relating to spans and loading. Having a manual for warm flat roof construction with details and a summary of rules to follow helps.

This demo version is fixed at 1m. The starting point involves laying roofing joists across the two upright items which in most cases will be the walls of the structure. Strutting is fixed between the joists to. 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.