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Timber frame construction details

The fire safety requirements for timber frame houses are the same as those for other forms of construction. The nature of timber frame construction does, however, give rise to particular aspects of detail that do not arise in the case of external walls comprised solely of masonry construction.

Timber frames have a far more combustible nature than traditional masonry; it is therefore a requirement that specific care is taken in the detailing and installation of cavity barriers and firestops. Unless recommended by the timber frame manufacturer, firestops and cavity barriers should be provided at required locations.

Floor fire resistance and structural steel fire protection

In general two-storey dwellings, the first floor is required to have a modified half-hour fire resistance. In dwellings with three storeys or more, the requirement changes and a full half-hour fire resistance is required. Normally this is achieved by incorporating either 15 mm plasterboard or 12.5mm fireline board into the floor structure by attaching it to the joists. The timber frame manufacturer’s guidance should be sought where fire-resisting constructions are required.

Structural steel fire protection

Supporting steel members to wall and floor are required to have fire protection. Typically, this is achieved by boxing in the steel with fire-grade plasterboard.

Precise specifications will vary with the period of fire resistance required and the type of steel member being protected. The timber frame manufacturer should provide all details relevant to the fire protection of steel members.

Cavity barriers and firestops

Cavity Barriers

Cavity barriers are required in the following locations:

  • At the top of external walls at eaves/verge level

  • If a party wall is present, installed horizontally at ceiling level

  • Around all opes (e.g. windows, door, flues, etc.)

  • At the intersection point between external and party walls.

Firestops

Firestops are required in the following locations:

  • At the intersection point between external and party walls.

  • Horizontally installed in the party walls at each floor level present.

  • Horizontally installed in the party walls at each ceiling level present.

  • At the eaves box.

  • At the top of the party wall at the underside of the roof level.

Firestops should be of non-combustible material, typically of the wire-reinforced rock fibre variety.