Terrain Categories & Wind Code
No simple set of rules can be given which will specify all the measures that should be taken to avoid wind damage to tiled roofs in all geographic areas or at all sites.
The history of wind storm damage in Australia, however, indicates that reasonably simple precautions, as described in this manual and the attached AS 2050-1989 Fixing of Roofing Tiles, when applied in conjunction with local knowledge and experience, are usually sufficient to ensure the stability of the roof even in severe wind storms. Attention to the fixing of battens and tiles will, under all but the most exceptional wind forces, provide a satisfactory degree of security.
Tiles to Battens
Tiles should be mechanically fixed at or near the nose end. This is particularly important around the perimeter of the roof, and for overhangs beyond the line of the external walls.
Battens to Rafters
Taking the rafter material into consideration the fixing should resist the design uplift forces.
In locations where high wind (>47m/s) can be expected, sarking should be used irrespective of the roof pitch.
A roof pitch below 15% is not recommended for tiling without taking special precautions to ensure the weather resistance and competence of the roofing system. Indeed AS 2050-1989 Fixing of Roofing Tiles specifically notes that:
"The Standard applies only to roofs with a pitch of 15 or greater"
"Where it is intended to fix tiles to roofs with a pitch of less than 15 the
tile manufacturer's advice should be sought."
Pitches below 15 can be acceptable in specific circumstances and Monier products have been used on such installations for many years. However, in line with AS 2050-1989, such installations should be reviewed with the local Monier office.
Having noted the above, the minimum recommended roof pitch for each tile profile follows. While sarking is shown as being optional at an increased pitch, Monier recommends that sarking is used in all circumstances for its insulation and additional weatherproofing properties.
Minimum pitch is not advised for long rafter runs in order to prevent water inundation, and again sarking is recommended. As a general guide for contoured tiles, rafter length should not exceed 4.5 metres at minimum pitch. For each 0.5 metre increase in rafter length above 4.5 metres, the pitch of the roof should be increased by 1 up to 22 which is an acceptable pitch for long rafter runs. Refer to the supplementary tables regarding pitch and maximum rafter length as related to sarking and flat profile tiles.
Division of Work
Work to be carried out by the tile fixing team and by other trades, e.g. builder or plumber, varies slightly from State to State but generally the following applies.
Work by Other Trades
Work normally carried out by other trades prior to tiling would include the following:
- Installing all rafters and trusses and all permanent and temporary
- Securing the roof structure.
- Installing all above-rafter boarding and ceiling sheeting.
- Installing counter battens, if required.
- Installing bellcast (tilting) battens, if required.
- Installing gutters and drainage pipes.
- Installing fascia boards, and barge boards, if required.
- Installing flashing and flashing supports.
- Installing roof ventilation, other than vent tiles.
- Installing valley boards and valley irons.
- Installing safety mesh, where required.
- In Victoria and Western Australia, fixing anti-ponding facilities.
The tiling of the roof would normally include the following operations:
- Lying anti-glare reflective foil or sarking, and if required, fire-resistant
batts over party walls.
- Fixing anti-ponding facilities, if required.
- Fixing tile battens.
- Fixing tiles and accessories.
- Bedding and pointing.
- Cleaning down.