Sandstone cleaning and sealing in Frenchs Forest

Many Frenchs Forest homes sit on generous blocks with sandstone used throughout the garden: retaining walls along the slope, natural outcrops kept as features, steps between levels and paving around outdoor areas. The stone nearest the bush, or under large gums, is usually darkest, with black mould, green algae and brown tannin stains. Exposed outcrops and wall caps carry lichen. Some properties also have older sandstone from before the area's recent redevelopment, which may be softer and more weathered. Our technicians assess each area, identify what is growing on it, and trial a cleaner on a small patch before starting the full job, adjusting strength for older stone.

We dose mould, algae and lichen with a natural-stone biocide and wait for it to work right through, then clear the dead growth by brush and with a light rinse. Natural outcrops are never pressure-blasted, since that strips the weathered skin that protects the rock. Tannin stains are treated with a targeted cleaner, and a poultice draws out deeper marks. Acid has no place on sandstone, because it reacts with the iron in the stone and causes orange staining. Leaves are cleared before work begins so fresh tannin does not run onto cleaned stone. Bunds and a wet vacuum keep the wash water out of the bush and the street drains.

Well-drained paving, steps and wall caps are suited to a breathable penetrating sealer, which holds back growth and tannin and makes leaf litter easier to clear. Retaining walls in front of damp soil, and outcrops in contact with the ground, go unsealed. Under tree cover, stone may need several dry days before sealing. You choose between natural and enhancing finishes from samples on your own stone, and we apply thin coats with no surface film, then log the product and date. Thinning overhanging branches and keeping gutters clear will extend the result, and we point out any changes like that which would help your property.