Electrics and gas
What is a back boiler, and why is a neat gas fire not a service record?
A back boiler is a boiler hidden behind a gas fire, heating water as well as the room. The fire can look fine while the boiler and the flue do not. A home survey does not strip the fire or test the gas. Only a Gas Safe registered engineer should work on gas appliances. HSE is explicit that gas work is for those engineers.
Last reviewed 24 October 2026. Written for buyers in England and Wales unless this answer says otherwise. No named surveyor has signed this page. It is general guidance, not a report on your house, and not legal advice.
What is the fuller explanation?
These units are often old. A surveyor may see scorching, a flue that looks obstructed, or no ventilation where ventilation is needed. That is a reason not to use the appliance until it is checked. It is not a condemnation written as a certificate, and it is not a clean bill because the coals were tidy.
Ask the seller for any Gas Safe record. If there is none, commission one before you rely on the boiler. There is no national price in the RICS guide for that visit. Do not deduct a full heating-system replacement until an engineer has said the unit, rather than the radiators, is the problem.
What should you ask your surveyor?
- Could you tell there is a boiler behind the fire?
- Did you see ventilation and the flue, or only the case?
- Are you telling me not to use it until it is checked?
What are the typical next steps?
- Do not light it as a test.
- Book a Gas Safe engineer for the appliance, not a general surveyor for a second look.
- Keep radiator condition, if noted, separate from the boiler verdict.
Costs vary with the building and with who you instruct. Where this page does not cite a published figure, ask the surveyor, a relevant specialist, or your solicitor for a written quote. Do not treat a forum average as the price.
Also asked about this
Is a back boiler the same as a combi in a cupboard?
No. A combi is a different appliance, usually visible in a cupboard or on a wall. Both still need a gas engineer, not a survey, to be tested.
Does removing the fire leave a hole in the chimney?
It leaves an opening that has to be made safe and ventilated or capped properly. The survey does not do that work.