Timber Joist Flat Roof

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.

Timber joist flat roof.

Span tables for solid timber joists. For additional stability you can also use steel joists that are built into one or both of the walls. 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. Depth to width ratio should not be greater than 6.

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. Tables 1 and 2 in this chapter are derived from the trada technology ltd. 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. The section sizes are based on regularised als or cls timber.

Timber to be covered these span tables do not apply to timber which is fully exposed to the elements. The joists should be sized using either the trada span tables or bs en 1995. Joists are placed on edge spaced at 400 600mm centres supported by external and internal load bearing walls. Span is clear span between supports.

This will give additional stability to the roof structure. At least 40mm bearing on supports. 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. These span tables apply only to flat roof and roof with a slope of up to 10 degrees.

Maximum slop3 10 deg. For timber floors between homes. Floor joists flat roof joists assumptions at 400mm centers supporting permanent load excluding self weight of joists up to 50kg m2. 1 2 timber strength class and joist size.

Trada and approved document part a give guidance on sizes of joists for flat roofs relating to spans and loading. The construction of the flat roof is similar to that of the timber upper floor. 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.