Repointing stone walls in Langton Matravers

Rubble limestone elevations. A stone wall is not a brick wall with different units in it. The bed joints are uneven, the perpends wander, and the mortar does more packing than a thin brick joint. So we do not rake to a set depth. We take out what is loose, crumbling or friable, follow the decay back to sound material, and fill in stages so deeper voids are not left hollow. All of it with hand tools: an angle grinder on soft limestone takes the arris off and leaves a sawn line down a wall that was never straight. Joints are damped down before filling.

The mix, and where the joint finishes. 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. That means a breathable lime: an NHL or lime putty mortar gauged to the original sand, and BS EN 459 sets out which lime is which. The joint is kept a few millimetres back from the face, slightly recessed, so the aggregate shows and the stone reads as the surface of the wall. The weather struck and bucket handle profiles you see on brickwork have no business on a rubble elevation, and neither does a flush joint carried over the stone face.

Taking cement off stone. Much of what we do in the village is removing hard sand and cement pointing put on in the last fifty years. It is slow work with hand tools, because the cement is stronger than the stone and will bring a face away with it. Spalling gathers under sills and beside downpipes; where a face has gone we cut the stone back or replace it against a sample, then point the surround in the softer mix. A trial panel goes up first, judged on how it will look weathered.

Chimney stacks and brick dressings. The stacks here are often fired brick above the roof line even where everything below is stone. A stack takes weather on four sides with nothing warming it, so its joints go first and penetrating damp turns up on a ceiling below. We repoint the stack, renew the flaunching around the pots and make good the junctions. A low stack on a single storey range sometimes comes off a tower; anything on a main ridge wants a scaffold and is priced as its own line.

Boundary and field walls. Plenty of the walls along the lanes are built dry or nearly dry, with little more than earth and a lean lime between the stones. Pointing one solid in a modern mortar wrecks it: the wall loses the drainage it was built with. Where one is coming apart we bed and pin it back with a soft mix, or say it wants rebuilding rather than pointing.

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

Getting to it. A Victorian quarryman's cottage straight on the village street, a stone gable taking the weather off the ridge and a boundary wall along a lane 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.

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.

Walk the village and you can pick out the walls pointed in cement since the war. The giveaway is a band of grey mortar standing proud of the stone, spread wide across the face to save cutting back into the joint. It is called strap or ribbon pointing, and on a Purbeck wall it does two kinds of damage at once.

The first is what the conservation area is concerned with. A stone wall should read as stone with mortar between it. Ribbon pointing inverts that, so the wall reads as mortar with stone showing through, and the shadow lines that give a rubble elevation its texture disappear. That is a change of appearance rather than a repair. The second is technical: a hard cement band seals the one route water had out of a solid wall, so damp goes deeper and stays longer, and when the cement parts from the stone it takes a layer of face with it.

So ask any quote where the joint will finish relative to the face of the stone, and what happens to the existing cement. A quote that says nothing about either is a quote for a ribbon.

We cover Langton Matravers, Worth Matravers, Kingston, Acton and down into Swanage, broadly 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.