Quoting a plumbing job you cannot fully see behind the wall

1 day ago
3 min read

Introduction

A great deal of plumbing sits behind plaster, under floors and inside boxing. A customer wants a fixed price and the honest answer is that nobody knows what is in the wall until it is opened. Quote a firm figure and you carry every risk; refuse to quote at all and the customer books somebody who will.

The way out is not a higher fixed price. It is separating the part you can see from the part you cannot, and pricing them differently and openly.

Customers accept uncertainty when it is explained. What they do not accept is a fixed price that changes without warning. The warning is the whole difference.

1. Quoting a plumbing job you cannot fully see means splitting the quote

Two categories, priced two ways.

Fix the price on what is visible and known

The boiler, the bathroom suite, the labour to fit it, the materials you can count. That part can be firm. Most of the quote will sit here.

Price the unknown as a stated rate

An hourly or day rate for anything found behind the wall, with an estimate of the likely hours. Honest and easy to explain. Give a likely range as well as the rate.

2. Investigate before quoting where you can

Some uncertainty is removable cheaply.

Lift a board or open an inspection point

Twenty minutes of looking frequently converts a guess into a price. Ask permission and do it at the survey. Take a torch and a screwdriver.

Charge for a paid survey on larger jobs

An hour of proper investigation, priced, credited against the work. It protects you and produces a better quote. Say it is credited if they proceed.

3. Name the specific risks in writing

Vagueness is what causes disputes, not uncertainty.

List what might be found

Lead pipe, asbestos-containing material, non-standard fittings, corroded steel, no isolation valve. Name them rather than referring to unforeseen circumstances. Customers accept named risks and distrust vague ones.

Say what each would cost, roughly

A stated additional figure for each named possibility. The customer can then budget for the worst case rather than being surprised by it. Most jobs come in below it.

4. Set the rule for stopping and calling

The moment of discovery decides the relationship.

Agree that you will stop and ring

Before incurring anything beyond the quote. A customer consulted is a customer who agrees; one informed afterwards is a complaint. Agree it before you start, in writing.

Photograph what you find

Nobody can see inside their own wall. An image resolves the conversation instantly and permanently. Send it before you telephone.

5. Do not absorb it to keep the peace

Absorbing found work is a habit that compounds.

Charge for genuine additional work

Discovering a problem is not your fault and fixing it is real labour and real materials. Quote it before doing it.

Own your own omissions separately

If you could have seen it at the survey and did not, absorb that and say so. The distinction is what makes the rest credible. Customers can tell the difference.

Conclusion

Split every quote into what you can see and what you cannot: a firm price on the visible work and materials, and a stated rate with an estimated range for anything found behind the wall.

Remove what uncertainty you can by lifting a board at the survey, and charge for a proper paid investigation on larger jobs, credited against the work. Name the specific risks in writing — lead pipe, asbestos, corroded steel, no isolation valve — with a rough figure against each, so the customer can budget for the worst case. Agree in advance that you will stop and telephone before exceeding the quote, photograph everything you find, and charge for genuine additional work while owning your own omissions plainly.