Cladding a Plinth with Natural Stone

Plinth cladding is the protective and decorative layer of the lower part of a facade between the apron and the ground-floor wall. The plinth receives the most moisture, splashes, snow, de-icing salts and mechanical impacts, so the most durable materials are chosen for it: natural stone of dense rocks, porcelain stoneware, clinker, facade panels.

The key selection criterion is the water absorption and frost resistance of the cladding, plus correct waterproofing beneath it. The best natural stone options are granite, basalt, dense dolomites and quartz sandstones.

This article is for private homeowners, designers and developers who are choosing a plinth finish and want to avoid typical mistakes. More articles on stone are in the section Natural stone for facades and interiors.

External plinth cladding material must meet several requirements:

• Low water absorption: the stone must not accumulate moisture from splashes, melting snow and capillary rise.

• High frost resistance: the plinth goes through dozens of freeze-thaw cycles per season while wet.

• Strength and impact resistance: the plinth suffers from shovels, lawnmowers and wheels.

• Resistance to salts and de-icers, especially for houses along roads and pavements.

• Compatibility with the substrate: for a pile foundation and a plinth on piles, the cladding is fixed to a frame or skirt wall, not to the ground.

Plinth cladding options and their features:

For cladding the plinth of a house on piles, frame-based solutions are more common: panels, profiled sheet or stone on a substructure. For a strip foundation, natural stone cladding on adhesive or on a rainscreen system works well.

Which natural stone to choose for plinth cladding:

• Granite is the benchmark for plinths: water absorption usually below 0.5%, high frost resistance and impact resistance. Finishes: flamed, bush-hammered, split.

• Basalt: dark, dense, does not show dirt.

• Dolomite for plinth cladding is popular in the south: dense grades perform well on plinths but need water-repellent treatment.

• Quartz sandstone: strong, non-slip, in warm shades; flagstone or sawn tiles.

• Dense travertine and limestone: only dense grades with proven frost resistance and protection.

Shell limestone, porous limestones and soft sandstones are not recommended for plinths: they quickly get wet, develop efflorescence and are destroyed by frost.

Artificial stone for plinth cladding is a compromise: it is lighter and cheaper, but its durability depends on the quality of the concrete and its protection. Cladding a plinth with artificial stone follows the same technique as natural stone on adhesive: substrate preparation, frost-resistant adhesive, joint filling, impregnation.

Waterproofing is the foundation of a durable plinth. Even the most resistant stone will not help if the wall behind it is constantly wet.

1. A horizontal damp-proof course between the foundation and the wall, in sheet or liquid-applied form, stops capillary moisture rising into the masonry.

2. Vertical waterproofing of the plinth and foundation, liquid-applied or in sheets, under the cladding and below ground level.

3. Plinth insulation with extruded polystyrene or other moisture-resistant insulation, where required by the design.

4. An apron sloping away from the wall with drainage so that water does not stand at the plinth.

5. A sill flashing above the plinth if the wall cladding projects or is set back relative to it.

6. Water-repellent treatment of the stone after installation.

The junction between the cladding and the apron is designed separately: the stone must not stand in water. Usually a joint filled with flexible sealant is left, or the bottom course rests on a base profile.

There are two main ways to clad a plinth with natural stone:

1. Adhesive (wet) method.

• the substrate is cleaned, levelled and primed; a reinforced layer is applied over polystyrene;

• the stone is sorted by tone and laid out on the ground;

• installation from bottom to top on frost-resistant natural stone adhesive, applied to both the substrate and the back of the slab;

• large and heavy slabs are additionally secured with stainless steel anchors or cramps;

• joints are filled with frost-resistant grout; once dry, the stone is treated with a water repellent.

2. Rainscreen substructure. Slabs, usually 30 mm thick or more, are fixed to a metal frame with clips or concealed anchors. The method suits insulated plinths, pile foundations and buildings where the plinth continues a rainscreen facade. The ventilated gap prevents efflorescence and removes moisture.

TECHNOFORMA carries out natural stone cladding and installation of ventilated rainscreen facade substructures with its own installation team; measurements are taken by its own surveyors. The cost is determined after a site inspection.

Typical mistakes in plinth cladding:

• Porous stone (shell limestone, soft limestone) at ground level: it deteriorates quickly.

• No damp-proof barrier: the stone draws water from the foundation and efflorescence appears.

• Cement mortar instead of stone adhesive: stains, efflorescence, detachment in frost.

• Cladding resting on the apron without a joint: slabs crack when the ground moves, and water stands at the bottom course.

• No sill flashing above the plinth: run-off from the wall gets behind the cladding.

• Polished stone: every drop and splash of dirt shows on it.

• Working at sub-zero temperatures without special measures: the adhesive does not gain strength.

• Rigid cladding on frost-susceptible soil of a pile foundation without a frame: cracks after the first winter.

• Salt de-icers near the plinth in winter: they destroy even dense carbonate stone.

At the Dinastia club house in Kislovodsk, TECHNOFORMA designed and installed a facade using 700 m² of granite, 700 m² of porcelain stoneware and 6,000 m² of glass fibre reinforced concrete (GFRC). Granite and porcelain stoneware are typical materials for the lower, most heavily loaded part of a building. At the Dominanta residential complex in Makhachkala the company installed 13,000 m² of porcelain stoneware together with 14,000 m² of GFRC.

Other projects are in the TECHNOFORMA projects section. If you plan paths and steps after the plinth, read “Natural stone in landscaping: paths, steps, kerbs”.