Specification 2 Descriptions of elements referred to in Specification 1

This Specification sets out the descriptions of elements referred to in Tables S1C2a, S1C2b, S1C2c, S1C2e, S1C2f, S1C2g, S1C2h, S1C2i, S1C2j, S1C2l and S1C2m of Specification 1.

Masonry units of ashlar, calcium silicate, concrete or fired clay (including terracotta blocks) must be laid in cement mortar or composition mortar complying with the relevant provisions of AS 3700.

Gypsum blocks must be laid in gypsum-sand mortar or lime mortar.

Gypsum-sand mortar and gypsum-sand plaster must consist of either—

1. not more than 3 parts by volume of sand to 1 part by volume of gypsum; or
2. if lime putty is added, not more than 2.5 parts by volume of sand to 1 part by volume of gypsum and not more than 5% of lime putty by volume of the mixed ingredients.

Gypsum-perlite or gypsum-vermiculite plaster must be applied—

1. in either one or 2 coats each in the proportions of 1 m³ of perlite or vermiculite to 640 kg of gypsum if the required thickness of the plaster is not more than 25 mm; and
2. in 2 coats if the required thickness is more than 25 mm, the first in the proportions of 1 m³ of perlite or vermiculite to 800 kg of gypsum and the second in the proportions of 1 m³ of perlite or vermiculite to 530 kg of gypsum.

Plaster prescribed in Tables S1C2c, S1C2e, S1C2f, S1C2g, S1C2h, S1C2i, S1C2j, S1C2l and S1C2m—

1. must consist of cement and sand or cement, lime and sand; and
2. may be finished with gypsum, gypsum-sand, gypsum-perlite or gypsum-vermiculite plaster or with lime putty.

If plaster used as fire protection on walls is more than 19 mm thick—

1. it must be reinforced with expanded metal lath that—
   1. has a mass per unit area of not less than 1.84 kg/m²; and
   2. has not fewer than 98 meshes per metre; and
   3. is protected against corrosion by galvanising or other suitable method; or
2. it must be reinforced with 13 mm x 13 mm x 0.7 mm galvanised steel wire mesh securely fixed at a distance from the face of the wall of not less than ⅓ of the total thickness of the plaster.

Ashlar masonry must not be used in a part of the building containing more than 2 storeys, and must not be of—

1. aplite, granite, granodiorite, quartz dacite, quartz diorite, quartz porphyrite or quartz porphyry; or
2. conglomerate, quartzite or sandstone; or
3. chert or flint; or
4. limestone or marble.

The thicknesses of masonry of calcium-silicate, concrete and fired clay are calculated as set out in S2C10 to S2C12.

For masonry in which the amount of perforation or coring of the units does not exceed 25% by volume (based on the overall rectangular shape of the unit) the thickness of the wall must be calculated from the manufacturing dimensions of the units and the specified thickness of the joints between them as appropriate.

For masonry in which the amount of perforation or coring of the units exceeds 25% by volume (based on the overall rectangular shape of the unit) the thickness of the wall must be calculated from the equivalent thicknesses of the units and the specified thickness of the joints between them as appropriate.

The equivalent thickness of a masonry unit is calculated by dividing the net volume by the area of one vertical face.

The ratio of height between lateral supports to overall thickness of a wall of ashlar, no-fines concrete, unreinforced concrete, solid gypsum blocks, gypsum-perlite or gypsum-vermiculite plaster on metal lath and channel, must not exceed—

1. 20 for a loadbearing wall; or
2. 27 for a non-loadbearing wall.

If a wall of ashlar, solid gypsum blocks or concrete is plastered on both sides to an equal thickness, the thickness of the wall for the purposes of Tables S1C2b and S1C2c (but not for the purposes of S2C5) may be increased by the thickness of the plaster on one side.

(1) Where Tables S1C2e, S1C2f, S1C2g, S1C2h, S1C2i and S1C2j indicate that column-protection is to be plastered, the tabulated thicknesses are those of the principal material.

(2) The thicknesses referred to in (1) do not include the thickness of plaster, which must be additional to the listed thickness of the material to which it is applied.

In walls fabricated of gypsum-perlite or gypsum-vermiculite plaster on metal lath and channel—

1. the lath must be securely wired to each side of 19 mm x 0.44 kg/m steel channels (used as studs) spaced at not more than 400 mm centres; and
2. the gypsum-perlite or gypsum-vermiculite plaster must be applied symmetrically to each exposed side of the lath.

(1) For the fire protection of steel columns with gypsum-perlite or gypsum-vermiculite on metal lath—

1. the lath must be fixed at not more than 600 mm centres vertically to steel furring channels, and—
   1. if the plaster is to be 35 mm thick or more — at least 12 mm clear of the column; or
   2. if the plaster is to be less than 35 mm thick — at least 6 mm clear of the column; or
2. the plaster may be applied to self-furring lath with furring dimples to hold it not less than 10 mm clear of the column.

(2) For the purposes of (1), the thickness of the plaster must be measured from the back of the lath.

For the fire protection of steel beams with gypsum-perlite or gypsum-vermiculite on metal lath—

1. the lath must be fixed at not more than 600 mm centres to steel furring channels and at least 20 mm clear of the steel; and
2. the thickness of the plaster must be measured from the back of the lath.

A column incorporated in or in contact on one or more sides with a wall of solid masonry or concrete at least 100 mm thick may be considered to be exposed to fire on no more than 3 sides.

A beam, open-web joist, girder or truss in direct and continuous contact with a concrete slab or a hollow block floor or roof may be considered to be exposed to fire on no more than 3 sides.

(1) The spaces between the fire-protective material and the steel (and any re-entrant parts of the column itself) must be filled solid with a fire-protective material like concrete, gypsum or grout.

(2) The insides of hollow sections, including pipes, need not be filled.

The proportion of cored holes or perforations in a hollow terracotta block (based on the overall rectangular volume of the unit) must not exceed the following:

1. For blocks up to 75 mm thick — 35%.
2. For blocks more than 75 mm but not more than 100 mm thick — 40%.
3. For blocks more than 100 mm — 50%.

Masonry of calcium-silicate, fired clay and concrete for the protection of steel columns must have steel-wire or mesh reinforcement in every second course and lapped at the corners.

Gypsum blocks and hollow terracotta blocks for the protection of steel columns must have steel-wire or mesh reinforcement in every course and lapped at corners.

If a steel column or a steel beam is to be protected with structural concrete or poured gypsum, the concrete or gypsum must be reinforced with steel-wire mesh or steel-wire binding placed about 20 mm from its outer surface, and—

1. for concrete or gypsum less than 50 mm thick, the steel wire must be—
   1. at least 3.15 mm in diameter; and
   2. spaced at not more than 100 mm vertically; or
2. for concrete or gypsum not less than 50 mm thick, the steel wire must be either—
   1. of a diameter and spacing in accordance with (a); or
   2. at least 5 mm in diameter and spaced at not more than 150 mm vertically.

(1) If a steel column or steel beam is protected with either gypsum-perlite or gypsum-vermiculite plaster sprayed to contour and the construction falls within the limits of Table S2C26a or S2C26b, the plaster must be reinforced with—

1. expanded metal lath complying with S2C7; or
2. galvanised steel wire mesh complying with S2C7.

(2) The reinforcement must be placed at a distance from the face of the plaster of at least 1/3 of the thickness of the plaster and must be securely fixed to the column or beam at intervals of not more than the relevant listing in Tables S2C26a and S2C26b.

(3) For the purposes of Tables S2C26a and S2C26b—

1. “vertical” includes a surface at not more than 10º to the vertical; and
2. “horizontal” includes a surface at not more than 10º to the horizontal; and
3. “underside” means the underside of any horizontal or non-vertical surface.

The thickness of the fire protection to steel columns and steel beams (other than fire protection of gypsum-perlite or gypsum-vermiculite plaster sprayed on metal lath or sprayed to contour) is to be measured from the face or edge of the steel, from the face of a splice plate or from the outer part of a rivet or bolt, whichever is the closest to the outside of the fire-protective construction, except that—

1. if the thickness of the fire protection is 40 mm or more, rivet heads may be disregarded; and
2. if the thickness of the fire protection is 50 mm or more—
   1. any part of a bolt (other than a high-tensile bolt) may be disregarded; and
   2. a column splice plate within 900 mm of the floor may encroach upon the fire protection by up to a ¼ of the thickness of the fire protection; and
3. the flange of a column or beam may encroach by up to 12 mm upon the thickness of the fire protection at right angles to the web if—
   1. the column or beam is intended to have an FRL of 240/240/240 or 240/–/–; and
   2. the flange projects 65 mm or more from the web; and
   3. the thickness of the edge of the flange (inclusive of any splice plate) is not more than 40 mm.