Natural Stone, Artificial Stone, or Klinker Brick Cladding

Natural stone is cut or split from real rock such as granite, slate, sandstone or limestone. It is heavy, every piece is different, and the right type can last for decades outdoors. Not every stone copes with frost, though. Sandstone soaks up water and gets dirty quickly without a protective sealer. Marble is better kept indoors, because outside it tends to lose its polish over time. Before you buy, ask the supplier whether the stone is frost resistant.

Artificial stone is cast in moulds that copy real stone closely. Concrete-based pieces can be used inside and out. Gypsum-based pieces are lighter and easier to work with, but they belong only in dry rooms. They are not suitable for bathrooms or façades. The main advantages of artificial stone are lower weight, regular sizes and easier cutting.

Clinker brick slips are thin slices of fired clay that look like real brickwork. They absorb very little water, resist frost and are easy to keep clean. You often see them on façades, plinths and chimneys, and indoors in industrial-style rooms. Matching corner pieces are available, so a corner looks as if it had been built from whole bricks.

One thing people often overestimate is insulation. Thin cladding hardly insulates a wall at all. It protects the surface and changes how it looks, but it does not replace thermal insulation.

1. Checking and preparing the background. The tiler removes loose render, dust and old paint, checks how flat the wall is and fills larger dips. The background has to be firm, clean and dry.
2. Primer and waterproofing. An absorbent background gets a coat of primer. On a plinth that is exposed to moisture from the ground, a waterproofing layer is essential.
3. Setting out. The pieces are first laid out on the floor and mixed from several boxes, so the wall does not end up with colour bands. A level line and the corner positions are marked.
4. Bonding. Adhesive is spread on the wall with a notched trowel. Outdoors it also goes on the back of each piece. This is called back-buttering, and it prevents hollow spots where water could collect and freeze. Façades need a flexible, frost-resistant adhesive. Heavy stone needs an adhesive made for large, heavy pieces.
5. Cutting and corners. Pieces are trimmed around windows, doors and switches. Corners are finished with corner pieces or with alternating overlaps, so no cut edge shows.
6. Grouting. Once the adhesive has set, usually after about a day and sometimes longer according to the manufacturer, the joints are filled. The grout or pointing mortar must suit outdoor use and the material being used.
7. Cleaning and protection. Mortar residue is cleaned off before it dries. Natural stone and some types of artificial stone are then sealed if the manufacturer recommends it.

A flat, continuous wall without windows is a simple job for a tiler. These things make the work slower and more complicated:

• A broken-up surface with lots of corners, window reveals and cut-outs
• Irregular natural stone laid like a mosaic, where every piece has to be chosen and trimmed
• A poor background that first needs repairing, levelling or drying out
• Work at height that needs scaffolding
• Cladding over external wall insulation, where the insulation system manufacturer's rules have to be followed
• Weather, which limits outdoor work to warm, dry days

If your façade is insulated, keep in mind that not every insulation system can carry heavy stone. The system manufacturer sets which cladding and what weight is allowed, and whether extra mechanical fixings are needed. In that case lighter artificial stone or clinker slips are usually the more sensible choice.

If you plan to change the look of a house façade, check with your local building authority first. Rules differ from place to place, and the authority will tell you whether you need a permit, a notification or nothing at all. In a conservation area or on a listed building, the heritage authority also has a say. In a block of flats the façade is shared property, so do not touch it without approval from the owners' association or building management.

• Bonding with only a few dabs of adhesive, which leaves hollows behind the cladding that frost slowly pushes off
• Using ordinary indoor adhesive on a façade or plinth
• A plinth without waterproofing and cladding that runs right down into the soil, so water rises into it
• Gypsum-based artificial stone in a damp room
• Working in direct sun, in frost or just before rain, when most adhesive manufacturers state a range of roughly 5 to 25 °C
• Pieces from one box fixed side by side, so the wall looks patchy
• Dried mortar left on the face, which is very hard to remove from porous stone

In practice the problem is often not the cladding itself but a missing movement joint. Large areas and transitions between different materials need a flexible movement joint.

If you want to clad one wall in the living room or the area around a fireplace with lightweight artificial stone, up to a height you can reach safely from a stable stepladder, you can do it yourself. Leave façades, waterproofed plinths and any work on scaffolding to a tiler. Around a fireplace, keep the clearances from the firebox given in the fireplace manufacturer's instructions and use a heat-resistant adhesive.

1. Check that the wall is firm, dry and flat, and remove any loose plaster.
2. On plasterboard, ask the board manufacturer how much cladding weight the wall can carry.
3. Prime the wall and let it dry as stated on the product.
4. Lay the pieces out on the floor and mix them from several boxes.
5. Draw a level line for the first row using a spirit level.
6. Mix the adhesive as instructed and spread it with a notched trowel only over an area you can cover in time.
7. Press each piece in with a slight twist and keep checking that the surface is flat.
8. Cut pieces with an angle grinder and diamond blade, wearing safety glasses, a dust mask and ear protection.
9. Wipe adhesive off the face straight away with a damp sponge.
10. Once the adhesive has set, fill the joints and smooth them with a pointing tool.
11. Prime or seal the surface if the manufacturer recommends it.

• Rows are level and the wall looks flat when viewed from the side, with no pieces sticking out
• Tapping the cladding gives no hollow sound that would point to voids behind it
• Colours and shapes are spread evenly, without bands or patches
• Joints are full, of even depth and free of cracks
• Corners are clean, with no visible cut edges
• Pieces around windows, sills and switches are cut neatly
• The plinth has waterproofing and the cladding does not end directly in the soil
• Movement joints are filled with a flexible sealant
• No dried adhesive or mortar is left on the surface
• You have the names of the adhesive, grout and sealer used, for any future repairs