Kevin Taylor, Training and Technical Support Manager, outlines Marley’s top five tips for a successful and memorable clay pantile roofing project.
Clay pantile roofing projects combine the elegance and heritage of natural clay with outstanding aesthetic appeal and proven performance. As such, clay pantiles have remained a roofing product choice for clients seeking distinction on new builds or the refurbishment of an older property.
Working with clay pantiles is straightforward if professional contractors follow best practice installation guidelines.
1. Appreciate clay pantile characteristics
Always remember every clay pantile is unique. This is because it is a natural material and is fired in a kiln. The tiles will often have small variations in length and width, and slight deviations both in shape and colour.
2. Undertake important checks before starting
The first thing to establish with any clay pantiles is the length, as this can vary depending on the batch.
The length can be identified by measuring 6-10 tiles from different pallets. Once the length has been calculated, the batten gauge can be worked out to ensure the minimum headlap is maintained. The gauge can be open (i.e., variable) fixed (i.e., a set gauge) or limited (i.e., a shunt at the head limited by anti-capillary bars). In the case of the latter, it is good practice to batten the tiles up at the average shunt. By measuring the same 6-10 tiles across, it is also possible to check if there is any variation in the width.
3. Take the time to set out
When setting out more modern clay pantiles across the roof, it is essential to ensure they are kept in straight columns and are laying comfortably in the sidelocks. Or, for more traditional clay pantiles, within the confines of the mitered corners.
In addition, it is good practice to set out for a three or four tile width and to lay clay interlocking tiles at, or close to the average side shunt. This involves opening and closing the tiles and taking the average mark. These marks are transferred to the eaves and ridge battens and lines struck between them.
For traditional clay pantiles, it is good to lay a square (normally 4 x 4 or 5 x 5) of tiles on the battens to make sure they lay comfortably, before taking off the covering width of three or four tiles – it’s worth noting that there is no side shunt with traditional clay pantiles.
4. Mix up the clay pantiles for best results
When loading out the roof, it is important to mix pantiles from at least three pallets. This ensures any slight differences in the shade/colour of the tiles are blended evenly across the roof, as opposed to large bands of shade/colour which are detrimental to the final aesthetics of the roof and can take several years to weather in properly.
It is normal to find that every so often, a tile will not appear to be sitting correctly. Often, by swapping the tiles around, the tile will sit, but if it continues to be a problem, put the tile to one side and use this at the verge, valley, or hip where the distortion is not going to cause a problem.
5. Mortar considerations
When bedding ridges and hip tile in mortar, make sure the roofing mortar is mixed three sands to one cement, with at least a third of the sand being sharp sand. This ensures the mortar will be of the correct strength and durability when used in deeper beds, which are more typical with clay pantiles.
Clay hip and ridge tiles tend to draw the water out of mortar much more quickly than concrete ones, so it is good practice to wet or even soak clay hip and ridge tiles in clean potable water before bedding them on the roof. This is particularly important in hot weather to avoid flash drying which can lead to shrinkage, cracking, and premature failure of the roofing mortar.
Any pans deeper than 25mm should have dentil slips bedded into them to minimise the risk of sagging and shrinkage in the mortar. Traditionally, dentil slips were always bedded in mortar, but, in modern roofing, it is worth considering fixing them with a suitable adhesive, or a mechanical fixing if available.
Following these top tips can go a long way to achieving a better installed, aesthetically pleasing, clay pantile roof.
For more information on Marley’s clay pantiles visit Clay Roof Tiles | Clay Tiles | Marley.