KLH Online Tile Catalogue (for Local Projects)
Types of Materials

Terracotta Tiles (Spain, Italy)

What is Terracotta?
Terracotta is a form of unglazed earthenware, usually fired from red clay, characterized by longevity and retention of ambient temperature. It has a warm variegated color which can range from pinks through to cream and even ochre tints, this coloration, as well as the durability of the terracotta, being derived from the final firing conditions. When used on the floor, with wear Terracotta, achieves a patina which improves its overall appearance. 

How is Terracotta produced?
Traditionally terracotta was produced in wood fired kilns using a reduced air flow. The yellow/ochre color is due mainly to the blend of clays, but characteristic flash or flame marks occur if two tiles touch or are fired close together. 

These types of handmade terracotta are still often laid out on sand beds to dry, forming an interesting reverse side to the tile which is often used as the top, if an aged effect is desired. 

Spain produces many forms of Terracotta, from traditionally handmade terracotta's made in the south of Spain to mass produced machine made products. Spanish terracotta is probably the second most popular terracotta used in England.

Where can you use terracotta?

Terracotta is a porous material and will absorb water to differing extents depending on its porosity, which is in turn dependent on the type of clay used and the conditions under which it is fired. Most terracotta's are only suitable for indoor use as they absorb water which may then freeze causing the tile to crack or flake if subjected to frost. (Think of your terracotta plant pots).

When using terracotta out of doors, the substructure on which it is laid is also crucial, in that water below the terracotta may leak up under the surface and leach impurities up to the surface resulting in unsightly markings or damage due to frost. We would only recommend our Sitra terracotta for external use in view of its low porosity - as discussed above.

Characteristics of Terracotta

Chips, pits, salt pops and firing marks are all characteristics of handmade terracotta, even animal footprints are sometimes seen, all of which contribute to the character and individuality of the material - some of these characteristics can be seen in the adjacent picture. Salt pops are a result of the presence of calcium compounds within the clay and are particularly characteristic when the clay is only coarsely ground prior to forming the tiles. Rather like using baking powder, water in the adhesives and grouts used in the fixing process activates minerals within the deposit which expand at the surface leaving a small crater or salt pop.

Terracotta sizes and Design Ideas

We can supply a large range of different sizes of terracotta, and even shapes in some products, ranging from our 2.5x2.5cm taco inserts, through the sizes up to 40x40 cm - special shapes are also available to special order.  Material thickness vary from about 5mm for the smaller sizes up to 18 or 50mm for the larger dimensions.

There are a number of traditional designs used for interesting floor layouts, similar to those used for other flooring materials, and we have featured a number of these within our design ideas pages.  Different effects can also be achieved depending on which face is laid uppermost - a distressed aged appearance can be achieved with some terracotta by laying effectively upside down.  These often include the use of inserts, in either a glazed tile suitable for flooring, such as our sitra tiles, or natural stones such as marbles or slates, either machine cut or tumbled - see also our tumbled slate material and marble pages. We also supply centre feature designs - yes you guessed it, using our Sitra tiles, as well marble designs which can provide a stunning central focus point to a room.

Sealant
Terracotta must be sealed in order to prevent water absorption and staining. Some terracotta's may be supplied ready sealed but most will require treatment during and after laying.

The porosity of Terracotta can vary quite significantly, dependent on the type of terracotta and country of origin, which in turn will affect the choice of sealant and process used - in particular, for example, Mexican terracotta tends to be very porous.

Ideally, Terracotta should be sealed prior to fixing, to provide protection from staining etc. by tile adhesives. It is however normal to fix the terracotta and then seal prior to grouting, but care must be taken during the fixing process to ensure that the surfaces are kept clean and adhesives splashes or other substances are not allowed to remain on the surface of the tile for any length of time.

Traditionally, terracotta is sealed using boiled linseed oil, preferably double boiled. The oil is applied to the surface of the terracotta until no more can be absorbed. If after about an hour any puddling is seen, then the surface is wiped off with a sponge - excess sealant will dry in time on the surface and result in unpleasant staining.

For dense terracotta, such as the Sitra frost resistant range, and reclaimed terracotta , the linseed oil may need to be thinned down with methylated spirit to allow the oil to fully penetrate the surface. Once the terracotta has been oiled it should be left for at least 24 hours. The terracotta can then be grouted and once the grout is thoroughly dry, linseed oil is subsequently applied over the whole surface of the floor including the grout, any excess being removed.

It is strongly recommended that reclaimed Terracotta is thoroughly cleaned prior to sealing with an acid based cleaner.  TReclaimed terracotta is is normally very dense, and as such the above instructions for sealants may not be generic to this product. In particular, if a traditional linseed oil treatment is used, this will certainly need to be diluted with methylated spirits, and a small area tested prior to sealing a complete floor to  ensure there is no pooling of the oil.

For external use of terracotta it is strongly recommended that a waterproofing process is used such as that described within the FILA documentation. Linseed oil would not be recommended for terracotta which is to be used externally.

Although linseed oil treatment is the traditional method for sealing terracotta, the process can be rather time consuming and as such, proprietary sealants such as those from Fila discussed above are a good alternative.