Electrics and gas
A Rayburn and the boiler appear to share one stack. What has a visual survey not proved about either flue?
Not that either flue is sound. A Rayburn and a boiler that appear to share one stack have not had their flues proved by a visual survey. The survey can record two appliances and one chimney stack. It cannot see the liners inside the brick, prove the passages are separate, or show that fumes from one appliance stay out of the other. It has not swept either flue and it has not certified either appliance. Ask a competent person for each fuel to inspect the flues before you rely on both of them together.
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?
Sharing a stack is a picture of the outside, or of two appliances against one breast. It is not a drawing of the flues. A Rayburn may burn oil, solid fuel or gas, and the boiler may be a different fuel again. The passages inside the stack can be lined, shared, or blocked, and none of that is settled by looking at the pots or the cases. A visual survey does not open the flues and does not prove a safe route for either appliance.
Tell the next inspector that both appliances seem to use the same stack, and ask them to say which flue they could examine and which they could not. Do not light both appliances together as an experiment on a viewing. If one fuel needs a different competent person from the other, instruct both, and keep their notes beside the survey paragraph rather than guessing that the pots looked clear.
What should you ask your surveyor?
- What did you actually see: two pots, one pot, or only the appliances against one breast?
- Could you tell the Rayburn fuel and the boiler fuel from the cases?
- Was any flue liner, hatch or soot door visible, or was the stack closed?
What are the typical next steps?
- Ask a competent person for each fuel to inspect the shared stack.
- Do not fire both appliances together to test the flues yourself.
- Keep each flue note with the survey paragraph about the stack.
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
If both appliances have worked for years, are the flues proved?
No. A history of use is not an inspection of the liners. The survey still has not seen inside the stack or proved the passages stay apart.
Does one clear pot mean the Rayburn and the boiler are safely separate?
No. A pot shows an opening at the top of the stack. It does not show whether the passages inside the Rayburn and the boiler stay apart.