Timber Joist Flat Roof

1 2 timber strength class and joist size.

Timber joist flat roof.

Depth to width ratio should not be greater than 6. The construction of the flat roof is similar to that of the timber upper floor. Span is clear span between supports. 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.

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. 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. Maximum slop3 10 deg.

Eurocode 5 span tables for solid timber members in floors ceilings and roofs for dwellings 3rd edition. Joist breadth 47mm. Trada and approved document part a give guidance on sizes of joists for flat roofs relating to spans and loading. Joists are placed on edge spaced at 400 600mm centres supported by external and internal load bearing walls.

The section sizes are based on regularised als or cls timber. These span tables apply only to flat roof and roof with a slope of up to 10 degrees. The steels or rsj s rolled steel joists are often built into one or both walls to give added stability to the roof structure. Supporting imposed load for access and repair only.

The joists should be sized using either the trada span tables or bs en 1995. Timber to be covered these span tables do not apply to timber which is fully exposed to the elements. For additional stability you can also use steel joists that are built into one or both of the walls. For timber floors between homes.

Span tables for solid timber joists. Tables 1 and 2 in this chapter are derived from the trada technology ltd. The basic construction of a flat roof starts with roofing timber that is laid across two upright items usually two walls. Floor joists flat roof joists assumptions at 400mm centers supporting permanent load excluding self weight of joists up to 50kg m2.