The cement fillet around the base of this Warrington flue terminal had broken up and was letting water into the brickwork. We cut the crown back to sound material and re-flaunched the whole top.
This Warrington stack had reached the point where the flaunching was doing more harm than good. Flaunching is the sloped fillet of mortar that caps the top of a chimney and beds the pot or terminal into it. Its job is to throw rain off the crown and away from the open brickwork underneath. On this stack it had split, lifted and broken away in lumps, and what was left had gone soft and chalky to the touch.
Moss and lichen had settled into the cracks, which keeps the surface damp and works the splits wider every time the weather turns. Water was running into the top courses of brick instead of off them, and the grey flue terminal was sitting in a bed that no longer gripped it. That is the stage at which a chimney starts sending damp down the breast into the rooms below.
Our first photographs show it clearly. Around the back of the terminal the old fillet had broken off in slabs and left a rough, open face of weathered cement. Cushions of moss had rooted along the front edge, and the brickwork immediately below the crown was darker than the rest of the stack, which is usually a sign that it has been taking water for some time.
The brickwork itself was still sound enough to keep, with the mortar joints worn but not open. That kept the job to the crown rather than the whole stack. Where the joints have gone as well, the work becomes repointing as much as re-flaunching — that is what happened on our chimney leak repair in Warrington.
Everything loose, cracked and weathered came off the crown until we were down to material that would hold. The surface was then cleaned of dust, moss and debris so the new mortar had something to bond to; fresh mortar laid over a dirty face simply lifts again in a year or two.
We re-flaunched the whole chimney top in a high-strength, weather-resistant mortar, working it up from the outer edge of the brick and shaping it so that every face falls away from the terminal. The terminal was re-seated level and the mortar worked in tight around its base, then the surface was sealed off with the trowel to shed water rather than hold it.
Flaunching is exposed on every side and gets no shelter at all, so it wears out well before the stack does. From the ground you can sometimes see a pot leaning, or a dark stain spreading down the brick. From inside, it usually shows as damp on the chimney breast after heavy rain. Lumps of cement in the gutter are another giveaway.
If your stack is doing any of that, we look at chimneys across the borough — see chimney repairs in Warrington for the local page, or chimney repairs for the full list of work we take on. Send us a photograph through the enquiry form and we will tell you what we think it needs.
Tell us what the roof is doing and roughly where you are. We will come and look, and you get a written price before anything starts.
