Problems & Repairs
Something dropping into the fireplace is one of the few chimney faults that announces itself in the living room. It is also one of the most useful, because what falls is direct evidence of the condition of a part of the house nobody can see.
This guide is organised by what you find in the grate, since that is what you actually have to work with.
Fine black powder
Loose, dusty soot means normal deposit that has lost its grip, usually because the flue is due a sweep or because wind is disturbing it. On its own it is not alarming, but it is the flue telling you the deposit load is high enough to shed.
If it arrives in quantity after a windy night, add a cowl to the conversation as well as a sweep, since an open pot on an exposed stack takes the full force of the weather.
Hard shiny flakes
Glossy black flakes that feel brittle rather than powdery are creosote glaze breaking away. That is a more serious finding, because glaze is concentrated flammable deposit and it is the material behind most chimney fires.
It also tells you something about how the stove is being run: glaze forms when flue gases run cool, which means wet fuel, shut down burning, or a cold uninsulated flue. Clearing it matters, and so does changing what caused it.
Sand, grit and lumps of mortar
This is the one to take seriously. Mortar and brick fragments falling into the grate mean the flue is deteriorating internally, and in older unlined stacks that can mean the parging between the flue and the neighbouring rooms is breaking down.
A degraded flue can leak combustion gases into other parts of the house rather than sending them out of the top, so this is a stop and check finding rather than a sweep it and carry on finding. A camera survey is the sensible next step.
- Fine sand, joints eroding internally
- Mortar lumps, parging or brickwork failing
- Clay fragments, a damaged liner section
- Rust flakes, a corroding metal liner or flue pipe
Twigs, straw, feathers and mess
Nesting material. If it is spring or early summer the nest may be active and legally protected, in which case nothing should be disturbed until it is empty. If it is late summer or autumn, it needs clearing before the heating season, because nest material is a full blockage waiting to happen and it is also highly combustible.
Safe checks and what to leave alone
Collect what falls in a bag rather than sweeping it away, because it is the evidence and a sweep will want to see it. Note when it falls, whether it follows wind or rain, and roughly how much. Photograph the grate.
Do not push rods or a brush up blindly to see what shifts. If there is a loose mass above, the useful outcome is that it comes down in a controlled way with the fireplace sealed and a vacuum running, not in one go into the room.
Frequently asked questions
Is soot falling dangerous in itself?
The soot is mostly a mess and a dust hazard. What it indicates is the concern: a flue heavy enough with deposit to shed, or a structure breaking up above. Both need looking at rather than clearing up and forgetting.
Why does it only happen when it is windy?
Wind across the pot creates pressure changes down the flue that dislodge loose material, and downdraught pushes it into the room instead of letting it settle. It is a sign of both loose deposit and an exposed terminal.
The fireplace is not used, does it still matter?
Yes. Debris from an unused flue still tells you the stack is deteriorating, and an unused flue that is quietly breaking up affects the building rather than just the fireplace. Capping and ventilating an unused flue is worth doing.
Will a sweep tell me what the debris is?
Yes, and that is a large part of the value of the visit. What comes down, plus what the camera shows, gives you a condition report on the flue rather than just a clean.
Found something in the grate? Bag it and give us a ring
We sweep, identify the deposit and put a camera up the flue so you know whether it is routine or structural.