Stone tiles

Product types / variants

Limestone

Limestone  is a sedimentary rock that occurs naturally in the UK with a significant amount of quarrying from the South West of England through the Midlands to Yorkshire and the Humber. Imported stone from Europe and the Middle East is also used in Britain. Limestone ranges in colour from whites, beiges and creams through to blues and blacks. It has been used extensively as a masonry material for buildings, but hard limestones are also highly suitable for paving. It is less durable than sandstone, as a general rule, so care should be taken that it is sufficiently robust for use in high traffic or exposed locations.

Marble

Marble  is a metamorphosed limestone traditionally used in sculpture and as building stone. It is imported from around the world. Its wide spectrum of colours ranges from pure white to pinks, reds, golds, browns, greys and blacks. It can have irregular patches or substantial mineral veining. Its hard, durable nature makes it suitable for high traffic applications. When highly polished, the beauty of its visual characteristics is revealed, but this can be slippery and should be specified with caution for internal use. Honed and tumbled finishes are also common.

Slate

Slate  is available in indigenous varieties from Cumbria, Wales and Cornwall, as well as from several European countries, with Spain being the world’s largest producer. Brazil is also an abundant producer of slate. It is usually dark grey, blue or green in colour, although many other colours exist. It can be easily riven, making this a popular finish but it can also be sawn, honed, polished, flamed and tooled. High strength and low porosity make slate well suited to flooring applications, and it requires little maintenance.

Sandstone

Sandstone  is a sedimentary rock that has historically been sourced in the UK from the Pennines, the north of England and Scotland, although it is now also imported from China and India. Almost any colour is available, with tan, brown, yellow, red, grey, pink and white being the most common. Although historically used as a building stone or ornamental stone, because it is easy to carve, many types of sandstone are suitable for internal flooring. Some can be split or riven, but normally they have a sawn finish. Tooled, sandblasted, flame textured and antiqued finishes are also available. Sandstone is a porous material that should be impregnated and fully sealed when used internally.

Granite

Granite  is an igneous rock that is quarried in the UK, mainly in Devon and Cornwall, Cumbria, Peterhead, Aberdeen and on the east coast of Scotland. Imported granites are available from places such as Portugal, South Africa, India, China and Brazil. There is a very large range of colours on offer, which vary from fine to densely grained. Its hardness and low porosity make granite suitable for flooring. It is a very strong material and can take a fine polish, which best reveals its colours and patterns. However, this finish can be slippery and is more appropriate for cladding than flooring, where a textured surface would be safer.

Quartzite

Quartzite  is quarried in Ireland as well as in Norway, Sweden, Italy and elsewhere. In general, it is a strong, hard wearing material, with low porosity, making it suitable for flooring in high traffic locations. It is one of the hardest, most durable stones, and often has sufficient compressive strength to carry very high loads, meaning that thinner tiles can be specified.

Porphyry

Porphyry, most commonly sourced from Italy, is regarded as one of the strongest stones in the world and therefore suited to modern urban areas with their associated high loadings. It is traditionally purple or red, with greys, browns and buffs also available. Porphyry can also have good high anti-slip characteristics.

Travertine

Travertine  has a distinctive white, cream or buff colouring and is imported from countries including Italy, Spain and Turkey, where it is found near hot mineral springs. It is generally less durable than other stones, due to naturally occurring pitting and voids in the material. It is therefore used for internal flooring applications with light loading. The voids are usually filled with resin, but they can make it difficult to polish or hone the surface, and can lead to problems if the filler fails.

Applications

It is important to assess each individual stone for its suitability to the specific application.

Due to the variety of classifications and terminology used for stone, simplified descriptions are often used. If due care is not taken, a stone selected as a marble, for example, may actually be a limestone or a completely different type of stone that does not perform as expected.

BS EN 12440 (denomination of natural stone) addresses this classification issue and provides the correct procedure for identification of stone type and origin.

Finish and appearance

Colours

Stone almost always displays variation in hue and pattern from block to block. Stone producers recommend quarry visits so that designers and specifiers can witness first hand the colour range, banding and special finishes available.

Surface finishes

Sawn, honed and polished finishes give a formal look, especially when the tiles are of uniform size and arranged geometrically.

Riven, tumbled and tooled finishes may be used to blend with a historic or traditional building, or to give a more relaxed, homely look. Random laying patterns are best suited in these cases.

• Riven stone has a textured finish with natural clefts that occur when a stone block is split from its bed. It is a slightly irregular surface that provides a degree of slip resistance.

• Sawn stone has a smooth but slightly coarse surface. This method of production gives a more consistent thickness and width than rustic textures such as riven and tumbled. Sawn flooring often has an additional treatment applied, such as a honed or polished surface finish or a hand-applied texture.

• Honed stone has been ground to a smooth surface, but one that is not reflective. To achieve a shinier, glossy polished surface, further buffing and polishing is carried out on the stone.

• Polishing reveals the full colour and crystal structure of the stone, but makes stone flooring more slippery when wet. Honed and polished finishes are better suited to contemporary style landscape designs than riven and tumbled finishes.

• Tumbled finishes give a rustic appearance. Tumbled paving stones are placed in a machine that vibrates and gives them a worn look with an irregular surface and rounded corners.

• Antiqued finishes give a stone an artificially aged, distressed appearance by replicating wear and tear. Various methods can be used, including acid washing or other hand-applied techniques.

• Flamed, shot- or sand-blasted, and bush-hammered finishes are applied to sawn paving, typically for stone types that cannot naturally be riven. These finishes give a textured appearance and improve the slip resistance characteristics of the product.
– Flamed: a rough surface that is created by heating the stone, fracturing some of the crystals.
– Shot-blasted: a matt texture created by firing grit onto the stone under high pressure.
– Bush-hammered: a pneumatic tooling action that produces a pitted surface.

• Tooled finishes can be machine or hand applied to stone to achieve a specific effect, and include hand-picking (also known as dolly pointing), chiselling and other techniques.

Technical data

Thickness

• Floors: tile thickness will depend on the strength of the stone type and the expected use. 10 and 12mm are common thicknesses for areas with any degree of traffic. Thinner tiles tend only to be specified for applications with light loadings.

British and European Standards classify stone tiles as no larger than 610x610x12mm. Any tile thicker than 12mm is classified as a slab and covered under separate standards.

• Walls: for wall tiling, a thickness greater than 12mm will exceed the load-bearing capacity of nearly all wall substrates and must be mechanically fixed. Thicker stone cladding panels are fixed using support systems.

Dimensions

Tiles vary in size from 300x300mm up to 610x610mm. Larger tiles, such as 900x600mm are sometimes available, although according to British Standards, these are classified as slabs .

Dimensions have a significant impact on price: stone tiles (especially when riven) are cheaper when supplied as one-way gauged widths in random lengths, as his makes most economic use of the raw material. Specifying a dimensional two-way size is significantly more expensive – up to 25%.

Accreditation

BS EN 12057: 2004 Natural Stone Products – Modular Tiles – Requirements
BS EN 12058: 21004 Natural Stone Products – Slabs for Floors and Stairs – Requirements

Maintenance

Stone tiles should be sealed, as almost all stone types can be stained if left untreated.