Asbestos-cement cladding was popular due to its ease of installation and low cost.
Locally manufactured asbestos-cement sheet cladding was popular due to its ease of installation and low cost.
Installation was quick, sheets did not need to be painted and were considered to be fireproof.
While popular as a general cladding, profiled asbestos sheets were commonly used to line the walls of set-back porches irrespective of the cladding used on the remainder of the building.
Sheet sizes ranged from 6–10’ (1.8–3.0 m) long x 3–4’ (900–1200 mm) wide with a thickness of either 3/16” (5 mm), ¼” (6 mm) or ⅜” (9.5 mm).
Large sheets were either butt-jointed or the sheets could be moulded to form joints. They were fixed directly to the framing. Studs were spaced at 18–24” (450–600 mm) centres to suit the sheet width, and the edges of sheets were required to fully supported and fixed.
Vertical joints were covered by asbestos-cement or timber ‘D’ mouldings, while horizontal joints had a metal flashing covering the joint before the moulding was applied (Figure 1). Joints in both directions had a strip of bituminous fabric under the joint or they were sealed with a bituminous compound.
External corners were finished with timber boxed corners (see bevel-back weatherboards) or proprietary, asbestos-cement corner mouldings.
Smaller sheets, planks or shingles that were laid in an overlapping pattern were also available and commonly used. They were 24 x 12” (600 x 300 mm) and 3/16” (5 mm) thick and could have a flat or scalloped bottom edge.
The fixing of smaller sheets was onto 2 x 1” (50 x 25 mm) or 3 x 1” (75 x 25 mm) battens that were fixed horizontally to the wall framing. Before fixing the sheets, the battens were covered with bituminous felt laid horizontally over the battens. The sheets were then nailed to the battens through pre-punched holes.
To provide additional protection against damage to the relatively brittle sheets, they were fixed at closer centres lower down the wall which increased higher up the wall. Fixings were at 5¼” (133 mm) centres up to 7’ (2.1 m) from the base of the wall and 10½” (266 mm) higher up (Figure 2).
External corners were finished with specially shaped metal or timber corner mouldings, while internal angles were flashed with a metal angle or bituminous felt laid under the asbestos-cement sheets and extending for approximately 3” (75 mm) from the corner in each direction.
Note that cement-based sheets that are known to be pre-1988, and have corrugated profile or a dimpled back surface, are likely to contain asbestos and should be dealt with accordingly – see Health risks: asbestos.