Soft, porous, unforgiving

Sandstone Cleaning

Sandstone is the most commonly wrecked surface we see. It is soft, it is porous, it contains iron, and it punishes exactly the two things people reach for first: hydrochloric acid and a turbo nozzle.

Think Brick accredited
Fully insured
20+ years experience

Think Brick accredited

Fully insured

20+ years experience

Illawarra to the Highlands

Quick answer

How do you clean sandstone without damaging it?

Sandstone should be cleaned with low pressure and pH-appropriate chemistry rather than hydrochloric acid or high-pressure water. Acid reacts with iron compounds naturally present in the stone and can trigger permanent orange-brown staining, while high pressure erodes the soft matrix and leaves a pitted, sandy surface that soils faster afterwards. Biological growth is best treated with a biocide and allowed to die back before gentle rinsing.

At a glance

Avoid: Hydrochloric acid — triggers iron staining
Pressure: Low; wide fan, never a turbo nozzle
Common issues: Lichen, algae, salt attack, iron bleed
Optional finish: Breathable penetrating sealer

What goes wrong with sandstone

Coastal sandstone through the Illawarra, Jervis Bay and the Shire takes salt-laden air constantly. Salt crystallises inside the pores, expands, and pushes the surface off in flakes — a process called salt attack or fretting. Cleaning a fretting wall aggressively accelerates it dramatically.

Then there is iron. Sandstone contains iron compounds as a natural inclusion. Hit it with hydrochloric acid and those compounds mobilise and oxidise, producing deep orange-brown staining that is far worse than the dirt you started with and extremely difficult to reverse.

What we clean

Sandstone retaining and boundary walls, flagging and paving, capping and steps, pool surrounds, feature walls and cladding, heritage stone facades, and sandstone blockwork on older civic and church buildings.

Sealing

Where it suits the stone, a breathable penetrating sealer slows re-soiling and makes future cleaning far easier. The word that matters is breathable — a film-forming coating traps moisture behind the surface and on coastal sandstone that accelerates the salt attack it was supposed to prevent.

Coverage

Where we do sandstone cleaning

Illawarra

Wollongong · Shellharbour · Albion Park · Dapto · Kiama · Shell Cove

Shoalhaven

Nowra · Bomaderry · Vincentia · Huskisson · Berry · Culburra Beach · Ulladulla

Southern Highlands

Bowral · Mittagong · Moss Vale · Bundanoon

Sutherland Shire

Helensburgh · Engadine · Sutherland · Cronulla

Based at Warilla. Everything from Helensburgh to Ulladulla and inland to the Southern Highlands is inside our normal working area.

FAQ

Sandstone Cleaning — questions we get asked

Can you pressure clean sandstone?

At low pressure with a wide fan and correct standoff distance, yes. With a turbo or rotary nozzle, no — it cuts visible lines into the stone within seconds and leaves a surface that holds dirt worse than before.

Why has my sandstone gone orange?

Almost always iron staining, usually triggered by acid contact, bore or dam irrigation water, or rusting metal fixings above the stone. It is a different problem to surface dirt and needs a reducing treatment rather than a wash.

Will cleaning remove the lichen permanently?

Cleaning removes what is there. A biocide treatment kills the growth at the root so regrowth is much slower, but any shaded, damp masonry will eventually re-colonise. Most sandstone benefits from a treatment every few years rather than an aggressive clean every ten.

Keep reading

Need sandstone cleaning quoted?

Call 0448 882 780 or send photos through the quote form. We will tell you what the job needs and what it will cost, including when the honest answer is that you do not need us.

0448 882 780 Free quote