Setting Out and Laying
In particular with clay pantiles due to the shrinkage during the drying and firing process in their manufacture there will often be more natural variation in the tile dimensions than with concrete tiles. Therefore the tiles have to be laid to create the best fit, and regardless of how good the tiles are there will be some gaps generated that will vary from tile to tile.
In terms of headlap many traditional overlapping pantiles due to the corner cuts have little or no batten gauge variance and for setting out purposes should be treated as fixed gauge tiles. This means that the same batten gauge is used up the length of the rafter and the last top course tile course in most cases will need to be cut (at the head of the tile) to size, nail-holes re-drilled and nailed/screwed into the top course tiling batten.
With traditional overlapping single clay pantiles it is also very important that perpendicular lines are struck prior to laying these tiles. Traditional pantiles which are not of the interlocking variety use the roll of the tile as the sidelap and as such the sidelap is essentially fixed and determined by the design of the specific pantile with little shunt available.
The best method of determining the batten gauge to be used is to take a random sample of 12 tiles and lay them along the ground upside down with all the tiles shunted in. A distance should be measured over ten tiles and divided by ten. The same process repeated with the tiles shunted out and again the distance measured over ten tiles divided by ten. The distance should be measured from nib face to nib face where possible. The average of the two figures then used to set out the batten gauge. The same process should be used to determine the coursing. Take the same 12 tiles and lay them along the ground lapping the sidelaps, first shunting them in and then shunting out, measuring over ten tiles divide by ten and average the result. The horizontal coursing should be marked on the battens from eaves to ridge onto the battens with a coloured chalk line every third or fourth tile to help maintain the perpendicular lines up the roof. When laying the tiles, the batten gauge and the coursing must be maintained and this will minimize problems. As each tile is laid, an assessment by the tiler should be made to ensure that each tile fits correctly and should reject any that do not. The rejected tiles can be used somewhere else where they fit better.
For pantiles of the more modern interlocking type the sidelap is dictated by the proprietary nature of the interlock and coverlock design and the setting out advice given in the sections discussing large format interlocking clay tiles (profiled or flat) and large format concrete interlocking tiles should be followed. Similarly the headlap variance is dictated by the proprietary nature of the interlocking tile design and features such as nail hole positions and design, weather bars etc can all influence the headlap variance possible.
In general modern interlocking pantiles tend to be designed to afford some headlap variance unlike traditional overlapping pantiles which have little or none but tile manufacturer guidance and technical recommendations should always be followed in any case.
Dry Ventilated Ridge
Gas Flue Ridge Terminal
Ventilation Tile (connected to soil or mechanical extraction)
Ventilation Tile (for roof space ventilation)