Fire Wall Restraint Systems

Achieving up to 4 hours fire resistance

voestalpine Metsec Z and C-section side rail systems, combined with the appropriate fire resistant wall cladding system, have performed satisfactorily in fire tests up to 4 hours duration. The period of fire resistance is dependent upon the construction and materials used in the fire wall cladding, therefore certification for the fire resistance period should be obtained from the cladding supplier.

Accessories and column stays need no facility for expansion and are supplied as standard items. In isolation, the eaves beam is part of the roof system and therefore need not be fire protected. However, if the rail system is suspended from this beam, it then forms part of the rail system and requires fire protection.

Rail Expansion

Under fire conditions, the rails expand. To achieve the necessary movement, the column fixing cleat should be slotted longitudinally. All fixing bolts should be fitted with combustible washers which collapse under heat, thus loosening the bolts and allowing expansion. This reduces distortion and buckling of the rail, ensuring integrity of the wall construction.

Rail Configurations

Fire Wall Connection Arrangement

Connection details

1. Standard butt connection
2. Standard sleeve connection (sleeve arrangement is not to be staggered)
3. Butt connection with slotted holes in cleats (see slotted cleat detail)

Even Bay Sleeved Arrangement

The side rail to be used should be selected from the sleeved rail load tables.

Single Bay Butt Arrangement

The side rail to be used should be selected from the butt rail load tables.

The illustrations above indicate an odd bay arrangement of rails for a fire wall. Grids (1) to (5), are designed as sleeved systems with the sleeves and standard cleats positioned on the same column lines, simplifying detailing and keeping one type of cleat on each column. The slotted cleats are positioned at alternate columns. The end bay, grids (5) to (6), is designed as a butt system keeping the depth of section similar to the rest but increasing the gauge to maintain rail centres.

The philosophy of rail expansion under fire, is that, with the sleeved system, the rail is locked at the sleeved position and expansion occurs to the left and to the right of this connection into the slotted position. Whereas with the butt system one side is locked and the free end is allowed to expand into the slotted cleat.

Utilising the standard slotted cleat detail, the rail length for both systems equates to the distance of column to column less 35mm. When cleating, clearance between ends of rails should be increased to allow for expansion of the corresponding system, as shown.

Slotted Cleat Detail

Slotted cleat by others or to special order.

Fire Wall Combustible Washer Detail

Download our purlin technical manual for more information.