Split-Face Stone Cladding - (Concrete Fencing, External Plinth/Sill)

The usual places are concrete fences, gate piers, garden walls and the plinth of a house, the lowest strip of the façade just above ground level. The plinth takes the most punishment. Rain splashes onto it, snow sits against it in winter, and next to a path it gets hit by de-icing salt. Render in this zone tends to crack and get dirty after a few years. Stone copes with this much better.

One thing needs saying plainly: stone does not waterproof a wall. The plinth still needs a working damp-proof course and waterproofing, and water must drain away from it. The cladding is a protective and decorative layer. It does not replace waterproofing.

If you live in a block of flats, talk to the building management or owners' association before you change the plinth or façade. If the fence stands on a boundary, or the work clearly changes how the building looks, check with your local building authority what the local building regulations require. Do not assume that no permission is needed.

There are two basic types:

• Natural split stone, such as sandstone, andesite, limestone, travertine or slate. Every piece is different, the colours are lively and the surface ages well. It is heavier and the pieces vary in thickness, so fixing takes more work.
• Cast stone, also called manufactured stone: pigmented concrete cast in moulds. It is lighter, the pieces have an even thickness and it goes on more easily. The pattern repeats, but good products are hard to tell apart from natural stone.

For plinths and fences, choose stone that the manufacturer or supplier clearly states is frost-resistant and suitable for exterior use. Soft, porous types, including some limestones, can flake off in layers near the ground over time because of frost and salt. On an insulated plinth with polystyrene boards, a lighter stone is usually chosen. Always check how much cladding weight the insulation system manufacturer allows.

First the installer checks the background. It must be firm, dry, sound and free of dust, old paint and moss. New concrete has to cure properly first, usually for around four weeks. Loose render is knocked off and uneven areas are levelled.

On a plinth, the bottom edge needs thought. The cladding should not run down into the soil without waterproofing behind it. It normally stops a little above ground level, and a gravel strip is laid along the house so that rain does not splash back onto the wall.

Then comes the bonding. The adhesive should be flexible, frost-resistant and made for exterior use, usually class C2 to EN 12004, ideally with the S1 (deformable) rating for stone. The stone is fixed using the double-buttering method: adhesive goes on the wall and on the back of each piece, so no voids are left behind it. Voids collect water, which freezes in winter and pushes the stone off. Work runs from the bottom up, and pieces are mixed from several boxes to avoid patches of one colour.

The cladding is either laid with joints, which are filled with stone pointing mortar once the adhesive has set, or "dry-laid" with tight joints. Depending on the stone, a sealer is applied at the end to reduce water absorption and white salt marks. On a fence, a coping or cap with an overhang on top matters a lot. Without it, water runs in from above behind the cladding.

• Flat, solid walls with no openings or projections go quickly. Every corner, pier, opening or step means a lot of cutting.
• Corner pieces: if ready-made corners exist for the chosen stone, corners are quick and clean. Otherwise pieces have to be mitred and fitted by hand.
• Natural stone of uneven thickness needs more adhesive and more patience than cast stone of even thickness.
• Condition of the background: removing old render, levelling or sorting out a damp plinth adds work before the first stone goes on.
• Access and weather: a thick hedge, a flower bed right against the wall or very hot or cold days all slow things down.

• Fixing stone on a few dabs of adhesive, which leaves voids behind it, so the cladding falls off after a few winters
• Using an ordinary indoor adhesive instead of a flexible, frost-resistant one
• Fixing onto a dusty, wet or frozen background, or in direct sun, where the adhesive skins over before the stone is pressed in
• Leaving a fence without a coping, so water runs into the top joint and behind the cladding
• Taking plinth cladding down into the soil with no waterproofing and no drainage
• Laying stone from one box at a time, which leaves visible bands of different colour on the wall

Adhesive is usually used at roughly +5 to +25 °C. The exact conditions are on the packaging.

You can clad a low concrete fence or garden wall yourself if you have some patience and an angle grinder with a diamond blade. When cutting stone, wear safety glasses, a dust mask and ear defenders.

1. Clean the fence of dust, moss and loose material, wash it if needed and let it dry.
2. Lay the stones out on the ground next to the fence and mix pieces from several boxes.
3. Stretch a string line or mark a level line for the first row.
4. Mix the flexible frost-resistant adhesive as instructed, only as much as you can use within the working time on the bag.
5. Spread adhesive with a notched trowel on the fence and on the back of each stone.
6. Press the stone on with a slight sliding movement so the adhesive covers the whole back, and remove any adhesive that squeezes out.
7. Start with the corner pieces, then fill in the flat areas from the bottom up.
8. Cut pieces to fit at the edges and around piers with the grinder.
9. Once the adhesive has set, point the joints with stone mortar if you chose a jointed finish.
10. Fit a coping on top of the fence with an overhang and a drip edge.
11. When everything is fully dry, apply a sealer according to the manufacturer's instructions.

Leave an insulated house plinth, or one with damp problems, to a professional. A mistake there shows up across the whole wall.

• Stones do not sound hollow when tapped
• No piece moves or has cracked edges
• Colours and shapes are evenly mixed with no obvious patches
• Joints are full, without cracks, and there is no adhesive left on the stone face
• Corners are clean and corner pieces line up with the flat areas
• The fence has a coping with an overhang and water drips clear of the cladding
• The bottom edge of the plinth stops above ground level and water drains away from the house
• You have the product names of the adhesive, pointing mortar and sealer used