Sandstone cleaning and sealing in Avalon Beach

On Avalon's sloping bushland lots, sandstone is used for garden walls, retaining walls, steps and paths, often surrounded by trees. Under the canopy these surfaces rarely dry out, so black mould and green algae thrive, and lichen spreads across the tops of walls. Leaves falling onto paving and steps leave brown tannin stains, especially where they sit wet after rain. Closer to the beach and the headlands, the problem shifts toward salt: grey grime, white bloom and gritty surfaces. Older architect-designed homes may also have stone with previous coatings that have aged and discoloured.

Avalon sandstone is cleaned after a trial on a hidden patch, using a biocide to kill mould, algae and lichen at the root, after which the stone is brushed by hand and rinsed at no more pressure than it needs. Tannin stains are lifted with a specific cleaner or, if deep, a poultice. On older stone, we check for previous coatings before choosing a method, because some need stripping before the stone can be properly cleaned or sealed. No acid, which leaves orange staining in Hawkesbury sandstone, and no narrow high-pressure jets. Run-off is captured rather than left to soak into the bush.

Sealing is worthwhile on paving, steps and pool coping, especially where leaves fall regularly. A breathable penetrating sealer slows tannin uptake so leaves can be swept away before they stain, and near the beach it reduces salt absorption. Retaining walls and freestanding garden walls usually stay unsealed so they can breathe. Shaded Avalon stone takes time to dry, so sealing is a separate visit after a dry spell, with moisture checked first. On heritage-listed or older architect-designed homes, we discuss sealing with you before proceeding, as some stonework is best left unsealed.