Flat Roof Joist Construction

Joist is a term used in construction for load bearing planks that run horizontally or nearly to horizontally to ground.

Flat roof joist construction.

1 enter joist details 1 1 span and joist spacing. 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. The construction of the flat roof is similar to that of the timber upper floor. Ceilings and roofs excluding trussed rafter roofs for dwellings or ask your lbc surveyor for advice.

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. Suitable for uk building regulation approval. This demo version is fixed at 1m. Strutting is fixed between the joists to.

Flat roofs aren t architecturally logical as rain and snow will shed much more quickly off a sloped roof. 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. Flat roof joist calculator. Of course you don t need to live in a modern house to deal with a flat roof.

Rolled steel joists or rsj s are used to support joists in flat roofs. 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. Having a manual for warm flat roof construction with details and a summary of rules to follow helps. Yet for historic modern style buildings like this old house s cambridge tv project flat roofs are at the core of the architecture meant to reflect the broad horizontal lines of the natural landscape.

Trada and approved document part a give guidance on sizes of joists for flat roofs relating to spans and loading. Flat roofs with a slight slope can be achieved using trus joist tji joists and solid section products. The basic construction of a flat roof starts with roofing timber that is laid across two upright items usually two walls. What is the process of building a flat roof.

Flat roof joists. For additional stability you can also use steel joists that are built into one or both of the walls. 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.