Timber Joist Flat Roof

Tables 1 and 2 in this chapter are derived from the trada technology ltd.

Timber joist flat roof.

For additional stability you can also use steel joists that are built into one or both of the walls. The joists should be sized using either the trada span tables or bs en 1995. For timber floors between homes. If insulation is placed on top of the flat roof joists and as such the joists are not fastened to the boarding above the depth to width ratio should not be greater than 4.

Span tables for solid timber joists. 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. Should refer to trada document span tables for solid timber members in floors ceilings and roofs excluding trussed rafter roofs for dwellings or ask your lbc surveyor for advice. Joist breadth 47mm.

Trada and approved document part a give guidance on sizes of joists for flat roofs relating to spans and loading. 1 2 timber strength class and joist size. Span is clear span between supports. This will give additional stability to the roof structure.

All roof timbers including joists wall plates blocking strutting battens firings and noggings must be to be preservative treated unless the timber used is naturally durable. Supporting imposed load for access and repair only. Maximum slop3 10 deg. Notches are not to exceed 0 125 of the depth of the joist and are to be located between 0 07 and 0 25 of the span from the support.

At least 40mm bearing on supports. Depth to width ratio should not be greater than 6. The basic construction of a flat roof starts with roofing timber that is laid across two upright items usually two walls. The section sizes are based on regularised als or cls timber.

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 construction of the flat roof is similar to that of the timber upper floor. Eurocode 5 span tables for solid timber members in floors ceilings and roofs for dwellings 3rd edition. Timber to be covered these span tables do not apply to timber which is fully exposed to the elements.