The Texture, Relief, and Luster of Stone

A conversation with your designer about finishing your own house can turn into an endless series of not always obvious questions about the type of facing stone: smooth or textured? Rounded boulder or broken edge? With a regular pattern or none at all? Rough? Polished? Dark or light? And even once you have settled on the material itself, the variety of textures and treatments of natural stone can give even a seasoned mineralogist plenty to think about.

Today's article is a short guide to choosing the texture and shape of facing stone.

Texture

The surface quality of natural stone depends largely on its inherent properties. There are three types of textures:

Smooth

A polished texture gives the stone a mirror shine, bringing out its pattern, natural color, and structure; this treatment also increases durability and reduces water absorption. The only drawback is that polished slabs become slippery when wet.

Varnished — a matte, fairly smooth surface with no visible traces of processing, a well-defined stone pattern, and a faint sheen; it significantly extends the life of the flooring.

Crystallized — specific to marble: a thermochemical treatment transforms the upper layer of the stone into a hard oxide film. If the procedure is performed after grinding and polishing, the surface becomes almost mirror-like; if not, it takes on a muted metallic luster.

Rough

Ground: the surface retains traces of machining with an abrasive tool and has a roughness up to 0.5 mm in height. The color, pattern, and structure of the stone are revealed only slightly, while the overall tone is noticeably lighter. It makes an excellent surface for floors, steps, and decks.

Sawn tiles feature grooved tool marks. Sawn slabs are used for paving garden paths and for facing plinths and walls, but they are more often given further processing.

Heat-treated stone is rough, with traces of flaking; it brings out the color and texture of the stone beautifully. Heat-treated stone is good for finishing building facades, as well as patios and steps, since it has anti-slip properties.

Sandblasted — a uniformly grained surface produced under a jet of compressed air; this treatment is used for exterior work or in places where there is a risk of slipping.

Shell-shaped — with uniform depressions up to 4 mm deep, which makes the treatment highly decorative. Stone with this texture can be used both for the exterior of buildings and for interior design.

Aged ("antique") — etched and worked with metal brushes to imitate the natural weathering caused by sun and air. Stone with this treatment is used in interior decoration and landscape design; its advantage is that it only looks better with time and use.

Relief

Rock — a man-made imitation of wild stone, a rough surface treatment that leaves a random pattern of depressions and protrusions of 50–200 mm with no further processing; stone with this texture is used for exterior decoration.

Pierced stone has a highly textured surface, with burrs more than 7 mm high. It looks good in combination with polished elements.

The texture of bush-hammered stone is achieved by working the surface with a four-sided metal hammer (a bushhammer), after which the surface remains chipped to a height of 5 mm. The decorative roughness has a practical purpose as well: it reduces slipping. Bush-hammered stone is used mainly for paving sidewalks and walkways.

Rough and embossed textures are most often used for the facades of residential homes, but polished granite, gabbro, and labradorite also make excellent finishing materials for walls and plinths. The beauty of polishing lies in the shine and the way it reveals the depth of the stone's natural color, but chiseled and rock textures have a more natural look, fit more easily into the landscape, and are less demanding of outdoor conditions. Natural stone tiles (limestone, sandstone, travertine) with a sandblasted or heat-treated surface also look great on facades, while slate tiles are often left untreated.

Stone shape

Processing natural stone also gives it the required shapes and sizes. Facing stone is conventionally divided into two groups — sawn (processed) and jagged (raw).

Wild stone — textured, with chipped edges — is used to finish plinths and exterior walls, especially when the goal is to "fit" the house into the landscape. Rounded stones, boulders, and pebbles are used in finishing with no less success, thanks to their highly decorative quality. Most often, however, untreated stones with jagged edges — rubble masonry — are used for facing plinths, facades, and fences.

Sawn stone is available in the form of tiles, faced bars, butts, galvanized stone (slabs of varying size and irregular shape with smooth edges), noodles (solid rock sawn into plates), and end slicing (strips cut from the end face of a flat natural stone). Its range of uses is endless, since in this form the stone looks equally good in the exterior of the house, in the interior, and in landscape compositions.

Masonry

There are two ways to lay stone: seamless and with joints.

Seamless technology involves fitting the elements together like a mosaic. When laying with grouted joints, the stones are set with a gap of 1–2 cm between them, and the resulting gaps (joints) are filled with adhesive grout, sometimes in a contrasting color for a decorative effect. The need for grouting depends on the design concept.