The short answer
A chimney sweep cleans the inside of the flue and a roofer repairs the outside of the stack. If you light fires, you need a sweep. If mortar is crumbling, pots are loose or the stack leaks, you need a roofer. Many chimneys need both, in that order, and each should tell you honestly where their job ends.
What a chimney sweep does
A sweep works inside the flue. Brushes and rods or a rotary system remove soot, tar and debris from the inside of the chimney, and the sweep clears the throat above the fireplace and the smoke chamber. Many also carry a camera to look along the flue, and a smoke test to check the flue draws and leaks nowhere into other rooms. A sweep may find a nest, a collapsed liner or a blockage, and a certificate or note after the visit records what was done. For open fires and solid-fuel stoves, sweeping is regular upkeep that cuts the risk of a flue fire and keeps the appliance burning cleanly.
What a sweep does not do is repair the masonry. They may spot cracks, loose pots or a missing cowl while on site, but sweeping does not mend them, and a sweep who offers to repoint a stack from a ladder is working outside their usual trade. Ask what they can safely reach, and be wary of anyone claiming a fix without scaffolding.
What a roofer does
A roofer works on the outside of the stack, from the roof upwards. That covers repointing the joints, rebuilding the top courses, replacing flaunching, refixing or renewing pots and cowls, capping flues, and dressing the lead flashings and trays where the chimney meets the roof. The roofer also looks at how the stack behaves as part of the roof, since water entering at the base of a chimney can come from the slates or the gutter and not from the chimney itself. Our overview of chimney repairs in Basingstoke lists the work.
Roofers do not normally sweep. Some can arrange a sweep, and a sensible repair visit often follows a sweep, because soot and debris at the top of the flue need to be cleared before pots are replaced or a cap is fitted.
Which one do you need?
| What you notice | Who to call |
|---|---|
| Smoke in the room, poor draw, soot smell | Sweep first, then a flue inspection |
| Crumbling mortar or bricks falling | Roofer |
| Damp patch on the chimney breast | Roofer, and a sweep only if the flue is in use |
| Loose or cracked pot | Roofer |
| Bird or nest noises in the flue | Sweep to clear it, then a roofer to fit a guard |
| Fitting a stove or relining | Appliance installer, plus a sweep and building control |
Damp is the confusing one. A brown patch on a chimney breast usually means water entering from outside, through the flashings, flaunching or failed joints, or condensation from an unvented flue. The flue itself is not normally dirty, and sweeping will not cure it. Our guide to damp on chimney breasts explains how to tell the causes apart.
The order to do things in
If you use the fire and the stack needs work, the usual order is simple. Have the flue swept and inspected first, so any blockage or lining defect is known. Then have the roofer repair the stack with that knowledge, because there is no point rebedding a pot on a flue that is about to be relined. Finally, arrange a smoke test or a second inspection if the roofer has changed the top of the flue, for instance by fitting a new cowl or pot. If the fire is not used and you are capping the stack, the roofer deals with it and can tell you what ventilation to leave. That is covered in capping a disused chimney.
Questions to ask either trade
Whichever you hire, you can learn a lot from a few questions. Ask what they will inspect and how they will record it. Ask whether they can show you photographs of what they find, and what they will do if they find a defect outside their trade. A sweep who spots slipping pots should say so and recommend a roofer. A roofer who sees soot staining on the stack, or a bad draught, should suggest a sweep or a flue inspection. Be cautious of anyone who says everything is fine without looking, or who finds a long list of urgent faults on a ten-minute visit.
At Beacon, we look at the stack, flashings and roof, give you photographs and a fixed written quote, and say plainly when repointing is enough or when the flue needs separate attention. If you light a fire, we suggest having a sweep carry out their own check, because the inside of the flue is a different trade from ours.
What the repair costs, and where the sweep fits in
Costs differ widely between the two. Typical UK ranges reported by cost guides put chimney repointing at £450 to £1,200, and chimney repair as a whole at £500 to £2,000. Sweeping is a much smaller call-out and is billed separately by the sweep. Your fixed quote follows the survey, and it covers the roofing side only. For more on repointing, see chimney repointing.
Every roof is different. A free survey with photos settles it for yours.
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