What to ask before hiring a stone or brick restoration contractor

Most people hiring a stone or brick restoration contractor are doing it for the first time, on a building they cannot afford to get wrong. That is a difficult position to be in: the technical decisions that matter most — method, mortar mix, sequencing — are exactly the ones a non-specialist has no way to judge from a quote alone. This is a list of the questions that do the judging for you.

What method will you use, and why?

This is the single most useful question you can ask, because the answer tells you whether the material has actually been considered. A specialist contractor names the method — DOFF, TORC, poultice, hand cleaning — and explains why it suits the soiling type and the substrate. A contractor who answers with something vague ("we'll pressure wash it and see how it looks") has not diagnosed the building. They have picked the fastest tool in the van.

On soft or historic masonry — Portland stone, soft London stock brick, anything pre-1919 — pressure washing and sandblasting should be treated as answers that end the conversation, not start it. Both drive damage into the surface that cannot be undone. If a contractor proposes either as the default rather than something ruled out, that is the fastest way to identify a general contractor rather than a specialist.

Will I get a written method statement?

A verbal description of the plan is not the same as a written one, and the difference matters more than it sounds. A written method statement forces specificity: temperatures, pressures, dwell times, mortar mixes, sequencing. It is also the document that protects you if something goes wrong — there is a record of what was agreed, not just what was said on the doorstep.

If your building is listed or in a conservation area, a method statement is not optional; a conservation officer will expect to see one before consent is granted. We go into what a proper method statement needs to contain in our article on listed building consent.

Who will actually be on site?

Ask this directly, because the answer varies more than people expect. Some companies quote with one person and send a different, less experienced crew to do the work. Others sub the job out entirely once it's won. Neither is necessarily dishonest, but both change who is actually accountable for the decisions made on your building while you're not watching.

A named individual, on site, personally responsible for the method and the result, is a different proposition to a managed workforce. It is worth asking plainly: "who will be here on the day, and is that the person I'm speaking to now?"

Is there a trial panel or test clean?

A trial panel — a small, representative area cleaned first and assessed before the rest of the building is touched — is standard practice on any competent restoration project, listed building or not. It is the point where a wrong method reveals itself on a patch of wall, rather than across an entire facade. A contractor who proposes going straight to full works without testing first is asking you to accept the risk of the whole building on their first attempt.

Do they have experience with buildings like yours?

Ask for examples of comparable work — same material, similar age, similar problem — not just a general portfolio. A contractor who has cleaned modern brick extensively may have very little experience with the softer, more porous stock brick common in Victorian London, and the two require genuinely different handling. If your building is listed or in a conservation area, ask specifically about experience working with conservation officers and preparing method statements for consent. That relationship, covered in our guide to working with conservation officers, is its own skill, separate from the cleaning itself.

What does the insurance actually cover?

Public liability insurance is standard, but the level of cover should be proportionate to the building. A contractor working on a Grade I listed facade with irreplaceable carved stonework should be carrying cover that reflects that risk. Ask for the policy level, not just confirmation that insurance "exists" — and be cautious of any contractor unwilling to provide it in writing.

What's excluded from the price?

The cheapest quote is rarely the cheapest job, and the reason is usually in the exclusions. Scaffold access, waste removal, making good after repairs, and a written record on completion are sometimes quoted separately, sometimes not quoted at all. Two quotes that look £2,000 apart on paper are often quoting different scopes of work entirely. Ask each contractor to itemise exactly what is and isn't included before comparing figures. We cover the specific cost factors for stone cleaning in more depth in our article on London stone cleaning costs.

What happens once the work is done?

A specification-led contractor produces a written record on completion — the method used, the materials specified, any variations agreed on site. This becomes part of the building's file: useful for a future sale, for insurance, and for whoever does the next piece of work on the building in ten or twenty years. If a contractor doesn't mention this unprompted, ask whether it's included.