A full mortar bed on top of a compacted MOT Type 1 sub-base provides the most stable foundation. Dot and dab methods should be avoided as they leave voids under the slabs, which can cause the stone to crack or become unstable over time.
Natural Stone Paving Materials and Applications
Natural stone paving includes materials like sandstone, limestone, granite, and slate, providing a durable surface for outdoor spaces. These slabs feature inherent variations in colour and texture, with naturally riven or sawn edges depending on the finish. Many of these products are calibrated to a standard thickness, typically 22mm, which provides a consistent depth across the entire paved area. The dense mineral composition offers high frost resistance and standard slip-resistant properties, suitable for varying weather conditions.
These flags are typically laid to create patios, garden pathways, and structural borders. A successful installation requires a solid sub-base and a full mortar bed. Mixing cement with building sand creates a strong, supportive foundation that prevents the slabs from shifting or lifting under foot traffic. The uniform depth of calibrated stone makes it easier to keep the surface level, reducing the time spent adjusting the mortar mix during laying.
Once the paving is set, filling the gaps with brush-in jointing compounds prevents weed growth and stops surface water from undermining the mortar bed. The porous nature of some stone types means they can be treated with specific sealers to protect against staining from organic matter, while regular sweeping helps maintain the textured grip. The versatility in slab sizes allows for modular laying patterns, accommodating both traditional and contemporary outdoor designs.
Natural Stone Paving FAQ's
Sealing is not strictly necessary but it helps protect the stone from stains, algae growth, and colour fading. If you choose to apply a sealer, it is best to wait a few months after installation to allow any natural salts or moisture to escape from the stone and mortar.
Natural stone is best cut using an angle grinder fitted with a diamond-tipped masonry blade. Alternatively, a power saw with a water attachment will keep the blade cool and reduce dust. Always wear appropriate safety gear, including safety goggles and a dust mask, when cutting stone.
A joint width of 10mm to 15mm is standard for natural stone slabs. This gap allows enough space to properly pack in the jointing material, ensuring a solid seal that prevents water from seeping under the paving.
Pressure washing can be used carefully to remove stubborn dirt, but holding the nozzle too close can damage the surface or wash out the pointing between the joints. Use a wide fan setting and keep the lance at a distance, or use a dedicated stone cleaner with a stiff brush for a gentler clean.