Sandstone cleaning and sealing in Collaroy

Sandstone on Collaroy beachfront properties often looks older than it is. Walls and terraces facing the sand develop a rough, worn surface from wind-blown grit, a grey layer of salt and grime, and in places a powdery white bloom. Lower walls and stairs down toward beach access stay damp and grow algae. Further back from the beach, toward and beyond Pittwater Road, sandstone garden walls and paths deal more with leaf staining, mould and traffic grime than with direct spray. We begin by walking the property and recording which surfaces face the beach and which do not.

Cleaning beachfront sandstone is mostly about removing salt and growth without removing stone. Our technicians rinse surfaces with fresh water to dissolve surface salt, pre-treat growth with a biocide, and then lift the residue with hand brushes and a low-volume rinse. On surfaces already roughened by blown sand, we use the lowest pressure that works, and some sections are cleaned by hand. If a white crust keeps coming back, a poultice left to dry on the surface can pull salt out of the outer layer of the stone. All run-off is collected and taken away, not allowed to run down to the sand.

Collaroy sandstone that takes direct spray is a strong candidate for sealing, particularly paving, terraces, steps and coping. An impregnating sealer that still lets vapour out limits how much brine the stone takes up, and the surface stays matte and natural. Retaining walls and walls in contact with damp ground are usually left unsealed so moisture can escape. Before sealing, the stone is rinsed of salt and dried thoroughly, and we pick a calm day so blown sand does not land on fresh sealer. Beachfront stone needs the water-drop test every year, as protection wears faster than on sheltered paving.