Chimney repairs in Wisbech

The repairs, and what each one actually cures

Re-flaunching

The old mortar cap is cut off, the pots are re-set and a new flaunching is formed with a decent fall so water runs off rather than sitting on it. A small job with a large effect, because a cracked flaunching lets water into the top of the stack where it has the whole height of the chimney to work down through. Very often this and new flashings together cure a leak that has been blamed on the roof for years.

Repointing, and the mortar question

Repointing means raking the old joints out to a proper depth and refilling them. The depth matters, because a superficial smear of new mortar over old joints looks fine for a season and then comes off in sheets.

The mix matters more, and it matters more in Wisbech than in most places, because so much of the older stock here is soft brick built with lime mortar. A hard cement mortar on soft brick is worse than no repointing at all: the mortar ends up stronger than the brick, so moisture that used to escape through the joint escapes through the brick face instead and the face spalls off. On a listed building it may also put you the wrong side of consent as well as the wrong side of good practice. A firm that does not raise the mortar mix unprompted on a period stack is not the firm you want on it.

Flashings

New lead, dressed to the roof line, wedged into a chased mortar joint and pointed up. Code 4 is the usual domestic specification, and leadwork done to that standard will still be there when the covering around it is not.

What you want to avoid is the cheap version: a fillet of cement run down the junction, or self adhesive flashing tape. Both crack or peel within a few years on an exposed elevation, and both have to be stripped off before the proper repair can happen, so the cheap fix costs you twice.

Rebuilding above the roof line

Where the brickwork has spalled badly or the stack has begun to lean, the section above the roof comes down and is rebuilt, reusing sound bricks where possible and matching them where not. New flashings go in as part of the same job, because the leadwork has to come out to do it anyway.

Capping a disused stack

Where the fireplace has gone and the flue is redundant, the stack has two remaining jobs: keep rain out and keep breathing. A vented cap or a capping pot does both, shedding water while still letting air move up the flue.

Close a flue off completely at both ends and the moisture already in the brickwork has nowhere left to go, so it comes out as staining on the chimney breast in the room below. A great many unexplained damp patches on upstairs walls are nothing more complicated than this.

Taking a stack down is structural, and often a consent question too

Removing a chimney is a popular job. It takes away a maintenance liability, frees up floor space and removes a weak point from the roof. It is also the chimney job that goes wrong most often, largely because the difficult part of it is not roofing.

The critical point is that a chimney breast and stack are usually load bearing masonry, and they frequently provide lateral restraint to a gable or a party wall. Cutting a section out of the middle and leaving what is above it unsupported is dangerous, and it happens.

• Removal is building regulations work. Taking out a chimney breast or stack needs building control approval, and the structural support has to be designed rather than improvised.
• Anything left above must be carried. Remove the breast downstairs and leave the stack in the loft, and the remaining masonry has to sit on gallows brackets or a beam sized for the load.
• A shared stack is a shared decision. Stacks on terraces and semis frequently straddle the party wall, which puts the job squarely in party wall territory and makes it your neighbour's business too.
• The roof has to be properly closed. Removing to below the roof line means new rafters, battens, underlay and covering across the hole, matched to what is already there, not a sheet of something laid over the gap.
• Account for the flue you are losing. Anything still using it, a boiler, a stove or a ventilation path, has to be resolved before the stack comes down.

Then the appearance question, which in this town is not a matter of taste. Fenland District Council has ten conservation areas, and in a conservation area it takes extra control over the demolition of most buildings, whether they are listed or not, as well as over minor alterations. Removing a stack from a listed building, or from a building in a conservation area, is not something to assume you are allowed to do. Establish it before you budget for it, and read the listed buildings and conservation areas guide first.

There is a straightforward visual argument as well. On a terrace, a run of matching stacks is part of what the street looks like, and taking one out of the middle is noticeable from the pavement for as long as the building stands.