Repointing and lime mortar in Corfe Castle

Rubble walls and the wide joint. The bulk of the village is local Purbeck limestone laid in thin, roughly coursed beds with a good deal of mortar between and behind the stones, so a fixed raking depth is meaningless here. We take out what is loose, friable or crumbling, follow it back to sound material, and fill deep voids in stages. Hand tools only: an angle grinder on soft limestone leaves a sawn line down a wall that was never straight.

Ashlar and dressed work, which is a different job. Window and door surrounds, quoins and the better frontages use dressed stone with joints a couple of millimetres wide, and a rubble mix will not go into those. They want a fine lime putty mortar with a finer sand, worked in with a thin blade. Treating an ashlar joint like a rubble one is how a good frontage ends up coarse.

The mix. Purbeck limestone is soft and permeable and these are solid walls with no cavity, so the wall sheds water by evaporating it back out through the joint and has to stay breathable. That means an NHL lime or lime putty mortar gauged to the original sand for colour and texture, kept back a few millimetres off the face and brushed once it has taken up, so the stone reads as the surface of the wall. A weather struck or bucket handle profile belongs on brickwork; on stone the finish is flush or recessed.

Taking cement back off. Much of what we do in the village is undoing hard sand and cement pointing applied in the last fifty years. It comes off slowly with hand tools, because the cement is stronger than the stone and will lift a face away. Where a face has spalled we cut it back or piece in a matching stone against a sample, then point the surround softer so the repair is not the hardest thing on the elevation.

Brick stacks, and the Victorian additions. Even where everything below is stone, the chimney above the roof line is often fired brick. A stack takes weather on four sides with nothing warming it, so its joints wash out first and the penetrating damp lands on a ceiling below. We repoint the stack, renew the flaunching round the pots and make good the junctions. A low stack sometimes comes off a tower; anything on a main ridge is a scaffold, priced as its own line.

Garden and boundary walls. Many of the stone walls along the lanes were built with very little mortar and meant to let water through, so pointing one up solid takes that drainage away. Where a wall is shedding stones we bed and pin them back in a soft mix. Past that, we say so rather than sell you pointing that will not hold.

No rate per square metre: the square metres tell you almost nothing until somebody has looked at the joints.

Getting to it. A cottage straight on the village street with no pavement to stand a platform on, a stone gable set back off a lane and a boundary wall along a track are three different set ups. A chimney or gable wants a scaffold, a low wall a tower or nothing at all. How long the platform stands matters as much as how big it is, and the work at height rules make it a priced line.

The joints decide it, not the wall. Raking out by hand is slow, and on soft brick the only safe way, because a disc cutter widens the joint and takes the arris off. How deep the joints come back, and whether faces have already spalled, sets the hours far more than the area does. The mix matters as much: cement holds water against a soft brick and the face blows off in the first frost, while lime is the right answer on most pre-1919 walls here.

Comparing quotes? Ask how deep the joints are raked, by hand or by disc, what the mix is and whether it was matched, how many spalled bricks are cut out, and whether the scaffold is in. Two quotes for the same job are usually two different jobs.

Most villages have a handful of listed buildings. Corfe Castle has 134 entries, which changes the running order of a repointing job. On a listed building the mortar is not a finish applied to the fabric, it is part of the fabric, and replacing it in a different material or profile alters the character of the building. Doing that without consent is not a paperwork slip. It is an offence, and the owner carries it.

So the specification comes first and the trowel second. An application will want the binder named, the sand identified, the gauge stated and the joint finish described, and often a sample panel built on the wall first. None of that is quick, so allow for it. It also means a quote saying only that the wall will be repointed is no use here, because it does not say the one thing the council will ask about.

If your building is not listed you are still inside the conservation area, where appearance is controlled even though the fabric is not. Either way: get the mix and the finish written down before you agree a price, so what is quoted, what is applied for and what goes on the wall are the same thing.

We cover Corfe Castle, Church Knowle, Kingston, Harmans Cross and out to Wareham and Swanage, broadly BH20 and BH19, all of it under Dorset Council. You are dealing with Bournemouth Roofing & Building, the trading name of Bournemouth Roofing & Building Ltd, registered in England and Wales, company number 15471719, which you can look up in a minute. Thomas Hannen's business, and he prices every job himself. A verified customer's 10 out of 10 on Checkatrade. The site visit and the written quote are free.