Vaucluse sits on the sandstone headland at the harbour’s southern entrance, and the stone is everywhere: garden walls, retaining walls, steps down to the water, house bases, and natural rock shelves left exposed in gardens. Sandstone cleaning is one of the higher-value searches in exterior cleaning in Sydney, with advertisers paying over $4 a click for it, and in Vaucluse it is the core job.
Why Vaucluse sandstone goes black
Freshly cut Sydney sandstone is cream to honey coloured. Over years it darkens to grey and black. Most of that is biological: algae, lichen and fungi growing on and in the surface, especially in shade and on faces that stay damp. Some is airborne soiling. More: why Sydney sandstone turns black.
On the harbour side the growth is heavier. On the ocean side salt weathering is the bigger issue: salt crystallises inside the stone as it dries and breaks the surface apart, leaving honeycombed and powdering faces.
What not to do
High pressure is the most common way sandstone is ruined. The stone is soft and layered; pressure scours the face, opens the bedding planes and leaves a rough surface that collects dirt and growth faster than before. Acid cleaners dissolve the clay and iron minerals that bind the grains and can leave orange or white staining. More: what high pressure does to sandstone and can you pressure wash sandstone.
What works
A biocide applied at low pressure with dwell time kills the growth, which then releases and weathers off. Gentle rinsing and soft brushing removes loose material. Stubborn staining is treated with stone-specific products, tested on a hidden patch first. More: how to clean sandstone walls.
Expect improvement, not a new stone. Old weathered sandstone has character that aggressive cleaning destroys.
Steps and paths
Steps down harbour-side slopes are often in shade and wet much of the year. Growth on them is a slip hazard. Clean them gently, check for loose and cracked treads, and consider slip resistance before sealing. More: slip resistance and how to clean sandstone pavers.
Exposed bedrock
Natural rock shelves in gardens and along the foreshore are best left largely alone. Cleaning them back to bright stone looks unnatural, removes lichens that may be decades old, and the runoff goes straight into soil or the harbour. A light clean where the rock is used as a path or seat is reasonable.
Sealing
Sealing sandstone is a judgement call. A breathable penetrating sealer can slow staining and growth on paving and steps. On walls, especially old walls, it is often better left unsealed so moisture can leave freely. Sandstone sealing is one of the most expensive searches in the trade at over $10 a click, which tells you how often it gets sold. Ask whether it is needed before you buy it. More: should sandstone be sealed and sandstone sealers.
Heritage controls
Part of Vaucluse is within the Bell Street heritage conservation area, where Woollahra Council’s controls require sandstone walls and fences to be retained and original materials maintained. Gentle cleaning is maintenance; rebuilding or altering is not. More: sandstone care in Vaucluse and Watsons Bay.
See the Vaucluse maintenance calendar and our sandstone cleaning service.
