How Are Clay Roof Tiles Made?
After being dug from the ground, the clay used to make the tiles has to be weathered for around nine months to a year.
It is then ground into fine particles with water added to make the clay workable. At this stage grog (which is previously fired clay pieces ground down) is added to help reduce shrinking, cracking and warping during the firing process. This also naturally adds texture to the tile.
Historically, handmade tiles would been hand thrown into the mould before being finished. However, nowadays they are more often mechanically pressed either by hand or by using a hydraulic press to ensure a more consistent density and to speed up production.
The roof tiles are then handled and dried in several ways to create the different character variations of shape and colour. The shape is created either by hand or machine and the colour can be varied by adding different oxides. For example, manganese oxide fires to a darker colour.
Temperature variations within the kiln will also lead to variations in colour, with a higher temperature resulting in a darker tile.
Top Tips When Choosing Clay Roof Tiles
It is recommended that tiles are mixed from at least three crates to allow for variations within, and between, batches. Laying a roof using tiles picked from sequential crates (without mixing them) could result in pronounced stripes or blocks of colour on the finished roof.
The density of any roof tile is important as the denser the product, the less water it will absorb, which in turn means the tile is less susceptible to frost damage. It’s important to check that your roof tiles have been tested to BSEN 539-2:2013 (Determination of Frost Resistance) as a poor-quality tile could lead to expensive repairs or, at worst, a complete re-roof.
A handmade clay roof tile will typically cost up to 50% more than its machine-made counterpart but will in return offer more shape, texture and colour variation. The benefits of a handmade clay tile are all in the aesthetic and for period properties and those of character there really is no alternative.
Have you started a new project and looking for just the right tile? Give us a call to talk to one of our experts who can advise you on just the right rile for your project.
