The design and construction of the supporting structure and the subsequent fixing of the roof tiles is a complicated procedure involving not only the fixing of the roof tiles, but the input of information from various manufacturers and specialists together with preparatory work by other trades. The extent of input to be expected from these sources is as follows:

Information Supplied by the Designer or Main Contractor

The following information would normally be supplied by either the designer or the main contractor:

• Design wind velocity (m/s).
• Rafter or truss spacing and material.
• Roof pitch.
• Corrosion potential of the site.

Information from the Tile Manufacturer

The tile manufacturer would normally provide advice specific to the tile type and relative to the design wind velocity, regarding:

• The minimum pitch of the roof.
• The need for sarking.
• The maximum rafter length.
• The correct batten spacing and fixing systems.
• Batten fixing requirements where design wind velocity is >33m/s, including nail or screw dimensions.
• An appropriate tile fixing system.

Bracing

Adequate supports and braces are to be installed, and roof truss bracing must run diagonally. Where timber braces are used, they should run diagonally on the underside of the top chord.

Structural Accuracy

The building and roof structures must be square and straight, with dimensions true to specification. Before tiles are loaded onto the roof framework, certain work must be completed:

• Timber walls must be properly braced and all load-bearing internal partitions framed and braced.

• Chimneys, abutments, vent pipes, gutters and valleys must be installed complete with their flashings.

• Barge Boards and tiling battens (where applicable) must be installed.

It may be necessary to install additional temporary bracing until the roof is fully loaded.

Barge Boards

For barge bed and point finish on fibre cement strip, or similar, (unless metal flashing is used) all barge boards should be 6mm below the surface of the tile batten.

Conditions for Exposed Rafters

Sarking is required (regardless of roof pitch) and all counter battens must be positioned accurately over the rafter centre lines. Counter battens must be of adequate section to allow sarking to sag to comply with AS 1904-1976 and provide clearance between the sarking membrane, the ceiling lining and any additional insulation material.

Fascia Boards & Tilting Battens

Fascia boards (or tilting battens) to eaves should be secured to the rafters with the top edge of the board or batten 25mm higher than the tile batten thickness, e.g. a 25mm thick batten requires a distance between top of rafter and top of fascia of 50mm. These measurements should be reduced by 10mm if the roof pitch is less than 20.

Gutter Projection

The gutter should project about 18mm past the outside face of the barge board for square barge tiles and about 65mm for half round barge tiles. The gutter must be installed before commencement of tiling.

Hip Corners

Dummy creeper rafters must be installed at hip corners to ensure that normal rafter spacing along the eaves is maintained.

Ridges & Hips

Hip and ridge boards should have their top edges level with the top of the rafters.

Valleys

Metal valleys must be fixed in place prior to tile laying. The sides of the valley tray should extend about 220mm up each roof slope.

Fire Walls

Where timber battens are not permitted over internal fire walls a galvanised metal strap or angle (preferably gang nailed) is fitted to support tiles. This trap should overlap the ends of the battens by 120mm.

Gutter Projection

The gutter should project about 18mm past the outside face of the barge board for square barge tiles and about 65mm for half round barge tiles. The gutter must be installed before commencement of tiling.

Battens

Battens should be of good quality timber in long lengths and correct size, according to local requirements.

Timber type and stress grading (F Value) should be in accordance with AS1684-1979 Timber Framing Code, also AS 1748 and AS 1749-1978 Mechanically Stress-Graded Timber, where applicable. (Refer Batten Table for batten sizes applicable in each State).

Batten Size and Grade

Battens of the correct size and material type are to be supplied in sizes specified and in accordance with AS 1684-1979 Timber Framing Code (Stress Grade).

Nailing & Jointing

Battens must be nailed at every intersection with rafters or trusses to a minimum penetration of 19mm. All joins are to be located at the centre of a rafter or truss member. There must be no more than two adjacent joins on any one rafter or truss and no less than two continuous battens between such joins.

Hip & Valleys

Battens should be mitre cut where they intersect with all hip and valley battens, and should be secured by skew nailing. Where ridge security is required, a batten of the same dimensions as the tiling batten should be fixed on top of the hip and ridge boards, and the tile battens mitre cut and skew nailed.