Question answered
How often should a chimney stack be inspected?
The short answer
Look at your chimney stack from the ground each year and again after a storm, using binoculars in dry light. Check the mortar, brick faces, flaunching, lead and lean. Have a roofer go up and survey it when you see damage, a damp patch below it, or after a long gap since it was last checked, because a ground view cannot show the top or the back.
The stack is the part of the roof you see least, and it takes the worst weather. A short look from the ground at the right times catches most problems while they are small.
A yearly look from the ground
The early signs show without a ladder. Pick a dry day with good light, stand back far enough to see the whole stack, and use binoculars if you have them. Do it from every side you can reach, including a neighbour's garden if they agree, as the faces away from the road are often worse.
Look at the brickwork first. The mortar between the courses should be firm and set slightly back from the brick face. Sandy, missing or recessed joints are early signs. Bricks with flaked or peeling faces, called spalling, suggest frost has got in.
Then look at the top: the pots, the cement bed that holds them, and any cowl. Look at the lead around the stack's foot. Note any green growth, white salt marks and rust stains. Photos taken from the same spot each year show change at a glance, and make a handy record for a roofer.
After a storm, check again
The coast gets gales that test every stack, so a quick look after a bad blow is worth the effort. Sea wind pushes against the tall, narrow shape of a chimney far more than it does against a flat roof slope.
Walk round the house and check the ground, the path and the roof edge for fallen mortar, brick fragments or pot pieces. Look at the stack for a changed angle, a pot that has shifted or a bracket that has moved. Our page on stacks left after a chimney breast is removed explains why an unsupported stack is a particular concern.
Indoors, if it is safe, take a torch up into the loft. Look at the timbers next to the chimney for fresh tide marks, and sniff for a damp, earthy smell. Feel the wall of the chimney breast on the upper floor for cold, damp patches. If any of these have appeared since the last storm, the stack should be looked at properly.
What a surveyor sees that you cannot
From below, the top of a stack is largely hidden, and the back is invisible from the street. A roofer working from a safe platform can see the flaunching, the inside of the cracks, the rear of the lead and the state of the bricks under the pots. They can tap the mortar to hear whether it is loose, and check whether the stack moves.
We trace water to the place it begins. A stain on a bedroom wall may come from a failed flashing, or a gap in the pointing, or a cracked pot bed, or a gutter behind the stack. The inspection works from the damp backwards, then matches it to what we find on the outside. How long chimney repairs take depends partly on what the inspection turns up.
After the visit you receive pictures of the stack, and if work is needed, a written quote that gives one figure. If nothing needs doing, the report says that.
When to book rather than wait
Book a survey when any of the following appear: loose or missing mortar, bricks coming away, a visible lean, cracks that run through several courses, rust stains, fallen pieces, or a damp patch that has no other explanation. Book too if the stack has not been looked at in a long time and you have no record of its last repair.
Waiting makes the job bigger. Water in an open joint freezes, widens the gap and takes more mortar with it. A cracked flaunching lets rain into the stack, and the damage spreads to the brickwork below. Repointing is a modest repair; a rebuild is a much larger one. For a sense of where a stack can end up if the early signs are ignored, read about chimney rebuilds.
Do not climb to check it yourself. A stack that is already loose is the wrong place to put your weight.
Protection that helps between inspections
Between checks, keep the roof around the stack clear of moss and debris, and keep the gutters running so water does not back up near the chimney. If you want to treat the brickwork, read our page on chimney waterproofing sealants first, because a coating that stops the brick breathing can cause more trouble than it prevents.
Keep a simple log with dates, photographs and notes of any work done, since a pattern over several years says more than one look. If you are buying a house, look at the stack as well, and ask for any repair record.
Unused flues need ventilation, and a roofer can advise on caps and pot repairs when we survey. Our chimney repairs page sets out the full range of work.
Stack checks: two more questions
Can I use a drone or phone zoom to inspect my chimney?
Either gives a closer view than the naked eye, and the photographs are useful to a roofer. Neither shows how loose mortar feels or what is behind the pot bed. Treat them as a way to spot a problem, then have the stack surveyed properly if anything looks wrong.
Does an unused chimney still need checking?
Yes. Rain still falls on it, and an unused stack can be neglected for longer. Capped and ventilated flues need their caps looked at, and a stack with no fire beneath it can leak into a bedroom just as readily as one in use.
Tell us about your roof
Describe what is happening and we will call you back to arrange a visit.
- Photographs of what we find
- A written quote with one total price
- Or call 01903 299063
10-year workmanship guarantee, in writing.