How to choose a stone sealing contractor in Sydney

The Prestige Standard stone-care team · Published 5 November 2026 · Updated 5 November 2026 · 8 min read

Why the contractor matters more than the bottle

Good stone sealers are widely available. What separates a lasting result from an expensive problem is almost always the work around the sealer: how the stone was cleaned, whether it was dry, whether the product suited the stone and the exposure, and whether the excess was removed before it dried on the surface.

Sandstone and travertine also punish the wrong method in different ways. Sandstone is soft and iron-bearing, so high pressure erodes it and acid can leave orange staining. Travertine is calcium carbonate, so acid etches it and salt water attacks it from inside. A contractor who treats every surface the same way, with the same machine and the same product, will get one of them wrong.

A good first visit tells you a lot. Expect the contractor to walk every area with you, identify the stone, look closely at stains, holes, flaking and any existing coating, and ask about the property's history: when the stone was laid, what has been used on it, and what bothers you about it now. If they can quote from the kerb without touching the stone, they are quoting a standard job rather than yours.

The questions below are the ones we would ask if we were hiring someone to seal our own stone.

Questions to ask before you accept a quote

Method and pressure

• How will you clean the stone before sealing? Sealing locks in whatever is on the surface, so preparation is most of the job. Expect a specific answer for each problem: biocide for mould and lichen, degreaser for oil, poultice for rust.
• What pressure and nozzle will you use on sandstone? The answer should be low pressure with a wide fan, or a soft wash. Gosford Quarries, a Sydney sandstone supplier, advises low pressure only because high pressure strips particles from the face of the stone. Conservation guidance from the US General Services Administration starts with a garden hose and increases pressure only as needed.

Chemistry

• What products will you use, and are any of them acidic? On travertine and limestone the answer should be no acid at all. On sandstone, acid should be a rare, controlled specialist step with a test patch, not a routine wash. Heritage guidance first published by the Heritage Council of NSW notes that acids can bleach sandstone, cause uneven iron oxide colouring and leave salts behind.
• Can I see the product data sheets? A professional will name the products and share the technical and safety data.

Sealer type and why

• Which sealer, and why that one for my stone? Outdoors, the usual answer is a breathable penetrating impregnator that sits in the pores rather than forming a film. Dry-Treat describes its STAIN-PROOF impregnator as invisible and breathable, for example. The contractor should explain how the choice suits your stone's porosity, its exposure to salt, sun or shade, and the look you want.
• Natural or enhancing finish? An enhancer deepens colour, which some owners love and others don't. You should see both on your own stone before deciding. Our comparison of penetrating, enhancing and topical sealers explains the trade-offs.
• How will you check the stone is dry? Sealing damp stone traps moisture. Lithofin's guidance is to apply impregnators only to completely dry surfaces, and notes that newly laid stone can take weeks to months to dry out.

Test patches

• Will you do a test patch, and when will we judge it? Heritage cleaning guidance recommends trialling methods on a representative area next to uncleaned stone. Sealer makers say the same: test first, then judge once cured. A test patch should cover the cleaning method and the sealer, and you should see it dry.

Run-off, water and noise

• Where will the wash water go? In NSW it is an offence to pollute waters, and that includes putting anything other than rain into drains and gutters built to carry rainwater. The answer should involve bunding drains and recovering wash water, not hosing it down the driveway.
• How will you comply with Sydney Water's Water Wise Guidelines? Hosing hard surfaces is limited to purposes such as safety, health and surface contamination. Treating mould, algae and staining fits, but a careful contractor will still use low-volume equipment.

Licence, insurance and paperwork

• What is your licence number? See the next section.
• Can you send certificates of currency? Ask for public liability cover, and for workers compensation if they employ staff, and check the expiry dates.
• Will I get a written record? The product, batch or date, and the areas treated, so the next re-seal uses a compatible product. Some manufacturer warranties also depend on who applies the product. Dry-Treat's written warranty for STAIN-PROOF, for example, applies only when an accredited applicator does the work and the surface is maintained to its written system.

Licensing and written contracts in NSW

Contractor licensing for residential building and trade work in NSW is administered by Building Commission NSW. There is a specific licence category for minor maintenance and cleaning, covering non-structural maintenance and cleaning of existing structures. Its qualification areas include pressure washing, graffiti removal and brick cleaning, and applying protective coatings to surfaces.

A contractor licence is needed to contract for or advertise work in this category when the job is worth more than $5,000 including GST in labour and materials. You can check a licence, its categories, its expiry date and any conditions on the NSW Government's online licence check. The NSW Government's own advice is to get more than one written quote, ask for references and examples of past work, and not to pay any money without a written contract.

Residential building work over $5,000 also needs a written contract. Jobs between $5,000 and $20,000 can use a small jobs contract, and jobs over $20,000 need a full home building contract. The contractor must give you the Consumer Building Guide before signing.

Jobs under the threshold don't need a licence, but a written quote and scope still protect both sides. If your property is heritage-listed, in a heritage conservation area, or part of a strata scheme, there may be further approvals to sort out before work starts. Our regulations page covers these, and our guide to strata sandstone and common property explains how stone work is organised in apartment buildings.

Red flags to watch for

Most of the damage we are asked to fix comes from a handful of avoidable mistakes. Treat any of the following as a reason to ask more questions, or to look elsewhere.

• Acid washing travertine or limestone. Calcium carbonate stones dissolve in acid. An acid wash leaves dull, etched patches that can only be removed by honing. Our guide to fixing etched travertine shows what that involves.
• High-pressure cleaning of sandstone. A turbo tip or narrow nozzle held close cuts into the binder and leaves pale stripes and a sanded surface that soaks up dirt faster than before. The damage is permanent.
• Glossy coatings outdoors. Film-forming acrylic and polyurethane coatings look striking at first, then trap moisture and salt, cloud, peel and can become slippery when wet. Removing them costs more than applying them.
• No test patch. A contractor who won't test on your stone is guessing about the cleaner, the dwell time, the sealer and the final look.
• Clean and seal on the same day. Unless the stone was dry to begin with and only dry-cleaned, sealing straight after a wet clean traps moisture.
• One product for everything. Sandstone, travertine, bluestone and granite absorb differently and react differently. A single bottle for the whole property is a warning sign.
• Promises of stain-proof or lifetime results. The Natural Stone Institute is clear that sealers make stone more stain-resistant, not stain-proof. Re-sealing intervals depend on exposure and use.
• Run-off down the gutter. If the plan is to hose everything into the street, they are not managing the environmental side of the job.
• No licence number for a job over the threshold, or reluctance to put the scope, price and products in writing.

How to compare quotes fairly

Two quotes for the same terrace can differ widely, and the cheaper one is often pricing a different job. Put them side by side against the same list.

Once the quotes are aligned, the real differences become clear: one contractor may have allowed for stripping an old coating or refilling travertine holes that another missed. Our guide to sealing costs in Sydney explains what drives those differences.

What you can do before anyone visits

A little preparation helps you get better quotes and ask sharper questions.

1. Do a water-drop test. Put a few drops of water on several areas. If they bead, existing sealer is still working. If they soak in and darken the stone quickly, it isn't, or there never was any.
2. Take photos. Daylight photos of each area, plus close-ups of stains, flaking, holes and any peeling coating.
3. Find your records. The stone supplier, the installer, and any product used before. A compatible re-seal is much simpler than stripping an unknown coating.
4. Note what bothers you. Mould, staining, salt, slipperiness, dull patches or colour. Each points to different work.
5. Check your obligations. Heritage listing, conservation area, strata rules or a pool safety barrier near the work area.
6. Keep up the basics. Sweeping, rinsing salt off coping and using a pH-neutral stone cleaner won't replace sealing, but they keep the stone in better condition for it.

What we'd suggest you don't do is try to strip an old coating or acid-clean the stone yourself before a contractor arrives. Those are the steps most likely to cause permanent damage.

When a specialist is worth it

Sealing a small, sound, already-clean sandstone path with a penetrating product, following the label exactly, is within reach of a careful homeowner. A specialist earns their place when the stone is large in area, high, near a pool or the sea, heritage-listed, stained, salt-damaged, previously coated, or when you want an enhanced finish and need it to be even.

Our sandstone sealing and travertine sealing services start with a test patch on your stone and a written record of the products used. Pool edges are handled through our pool coping service, and limestone, bluestone and granite through natural stone sealing. We work across the Eastern Suburbs and Northern Beaches with vetted, insured technicians, and price each job on request after seeing the stone. Ask us the questions above through our contact page. We'd expect you to.

Sources

• NSW Government: Minor maintenance and cleaning work licence
• NSW Government: Checking your contractor or tradesperson is qualified
• NSW Government: Consumer Building Guide
• Georges River Council: Water pollution and the POEO Act
• Gosford Quarries: How to clean sandstone
• U.S. General Services Administration: Removing dirt from stone masonry by pressure washing
• Heritage Victoria: Cleaning masonry (adapted from Heritage Council of NSW, Cleaning Masonry Walls)
• Dry-Treat: STAIN-PROOF impregnating sealer product information and warranty conditions (Kebur)
• Lithofin: Natural stone outdoors, cleaning and care information
• Natural Stone Institute: Care and cleaning of natural stone