Grün Engineering

Can my old chimney be used?

Read time 3 min

Plenty of buildings already have a chimney. Whether you can use it depends on what the survey finds and what appliance is going on it. This guide covers lining, new stacks and how we decide.

Short answer

Often, yes. An existing chimney is often lined, which means a new flue is fitted inside the old one. If the survey shows it won’t suit the appliance, we put in a new stack instead.

What a liner is

A liner is a new flue that runs up inside the old chimney, from the appliance connection at the bottom to the top. The flue gases go up the liner. The old chimney stays where it is, around it.

We install flexible chimney liners. The exact system is confirmed for each project.

What the survey checks

  1. The routeWe measure, sketch and photograph the chimney and the connection to the appliance.
  2. The conditionInspections and condition checks on the chimney.
  3. The insideAn optional CCTV survey, recommended if you want a flue report or condition report. The camera goes down from the top, so we can see what you can’t from the roof or the plantroom.
  4. The applianceWhat’s going on the end of it, and whether the chimney suits it.

Lining or a new stack

Lining

  • Uses the chimney you already have.
  • A new flue is fitted inside it.
  • Often the answer when the survey shows the chimney suits the appliance.

A new stack

  • A new chimney, built for the job, such as a twin wall insulated chimney.
  • Stands on its own base, with supports where it needs them.
  • The answer when the old chimney won’t suit the appliance, or there isn’t one.

Which one depends on the survey and the appliance. Neither is always cheaper or quicker. That also depends on what the survey finds.

Diagram

Old chimney with a liner, or a new stack

The same appliance, two ways of getting the flue gases out. On the left, a liner inside the old chimney. On the right, a new freestanding stack.

Section of an existing masonry chimney beside a building, with a flexible liner running up inside it from the appliance connection at the bottom to a terminal on the cap at the top.

Existing chimney with a liner

Section of a new freestanding twin wall stack beside a building. The flue runs out through the wall into the stack, which stands on a base, is held by supports off the wall, and has a terminal at the top.

New freestanding stack

Simplified sections drawn to the same scale. The survey decides which one suits your building and appliance.
Stainless liner terminal and cap plate on top of an old brick school chimney at dusk
Sir Thomas Boughey Academy, Stoke-on-Trent, flexible chimney liner

About the rules

Chimneys have rules on size and height. We do the calculations and check the design against the current regulations. If the job needs building control or chimney height approval, we provide the calculations and drawings, and you or your consultant submit the application.

Design and calculations

Common questions

Asked most about old chimneys.

Anything else, call 01395 201950 or email sales@gruneng.com.

  • Can an old chimney be used for a new boiler?

    Often, yes. An existing chimney is often lined. Otherwise we put in a new stack, depending on the survey and the appliance.

  • What is a chimney liner?

    A new flue fitted inside an existing chimney. The flue gases go up the liner, and the old chimney stays around it.

  • How do you check an old chimney?

    We survey it. We measure, sketch and photograph the route, and check its condition. If you want a flue report or condition report, we recommend a CCTV survey down from the top as an optional extra.

  • Who applies for chimney height approval?

    You or your consultant submit the application. We provide the calculations and drawings.

Related

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Send photos of the chimney and the appliance details. A price normally comes back within 24 hours.

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