Lime repointing on the old walls of Ashmore

Lime pointing on solid walls. An old wall in Ashmore has no cavity. It keeps the weather out by being thick and dries through its own surface, so the pointing has to stay more open and absorbent than the material around it: a breathable wall.

Joints come out by hand, never with a disc cutter or angle grinder, to roughly twice their width and back to sound mortar rather than a set depth. Back in goes an NHL, a natural hydraulic lime, with a well graded sharp sand matched to what came out, finished flush or slightly recessed rather than the weather struck or bucket handle profiles you see on later work. Joints are damped down before filling, brushed back once the mix has taken up, then kept covered for days, not hours.

Undoing a cement repoint. This is the repair Ashmore walls need most, because it is the most damaging thing done to them. A hard sand and cement joint over soft handmade brick or flint stops the wall breathing, so water leaves through the face instead and the first sharp frost lifts it off in flakes. Spalling like that usually arrives with penetrating damp on the inside face after a wet spell, and the two have the same cause. You can spot it from the lane: joints standing slightly proud of a wall whose faces have gone hollow. Taking that out without widening the joint is patient work, and blown bricks are cut out and turned, or replaced with reclaimed stock against a sample held on the wall.

Flint panels and brick dressings. Where a wall is flint with brick quoins, arches and cills, the two want handling differently in one elevation. Flint is bedded rather than coursed, so raking to a fixed depth takes the bedding out from under the stones and loosens more than it fixes. We judge that face by face, re-bed loose flints, put the galleting back where the original had it, and cut out brickwork only where the face has gone. The mix for a flint panel carries a coarser aggregate, because the joints are wider and a fine mortar shrinks back and cracks as it cures.

Stacks and the courses above the roof. An Ashmore stack stands in clear air with weather on all four sides and nothing warming it from inside, so it carries the tiredest mortar on the building. Repointing above the flashing, cutting out perished brick and renewing the flaunching around the pots is normally the whole job. A tower will sometimes reach a low outbuilding stack, anything on a main ridge is work at height off a scaffold, and that is why access is priced on its own line.

Lane walls and copings. Lane walls in Ashmore have been clipped, rooted and rained on for a very long time and nearly all fail from the top down. Once a coping loses its bedding the water goes into the core of the wall and the frost does the rest. Repointing the coping and the exposed top courses early is quick work next to rebuilding a bowed length later.

We never price repointing by the square metre; the state of the joints decides the hours. Joint depth. Joints have to be raked back to sound mortar. Shallow failure is quick, but joints washed out deep on a weather side take far longer.

By hand. Raking out lime by hand is slow. An angle grinder saves time but opens the joint up and knocks the arris off, and on old soft brick that damage shows for good.

The mix. Too strong a mix holds water against soft brick, and the face comes off in the first hard frost. A lime mix matched for sand and colour costs more in time than an off-the-shelf mortar.

Spalled faces. Bricks with blown faces are cut out and replaced with reclaimed matches, counted one by one.

Getting to it. A thatched cottage with a stack on the ridge, a flint and brick wall along a lane and an outbuilding up a farm track each need different access. Under the work at height rules the scaffold has to be a line of its own rather than tucked into a rate.

Put these points to anyone else: the depth of raking and the tool used, the mix and how it was matched, the number of replacement bricks, and whether scaffold is included.

Ashmore sits higher than any village in Dorset, on the top of the chalk where the Chase runs out, and that changes the calendar of a lime job more than the specification. Lime does not go off the way cement does.

It takes up slowly and hardens over months by taking carbon dioxide out of the air, and while green it is vulnerable to frost, which expands the water in the joint and turns the mortar to powder, and to a drying wind, which pulls the water out before the mix has set. Both arrive earlier and stay longer at this height, and the wind up here has nothing in its way.

So the pointing season on the top of the Chase is shorter than most people expect. We work lime in Ashmore from spring through to early autumn, stop when frosty nights are forecast, and sheet finished elevations and hang damp hessian for days so they cure slowly instead of flashing off in the wind. If somebody offers to point an old wall up here in December, ask what they will do about frost protection, and read the published guidance on lime and cement mortars before accepting an answer that amounts to putting cement in the mix to make it go off quicker. That is the shortcut behind most of the damage on these walls.

Repointing in Ashmore, and in the villages along the top of Cranborne Chase towards Tollard Royal and Fontmell Magna, is 19.7 miles from our base in Boscombe. Ashmore and Fontmell Magna come under Dorset Council, and Tollard Royal, over the county line, under Wiltshire Council.

We are Bournemouth Roofing & Building Ltd, a company registered in England and Wales under number 15471719, and the person who samples your mortar and prices the wall is the owner, Thomas Hannen. Checkatrade shows a 10 out of 10 left by a verified customer. The visit is free, and the written quote, itemised by line, is free as well. Before you book a visit in Ashmore, you can read our customers' Google reviews, word for word, on our reviews page.

Most repairs in Ashmore need no application at all. What decides whether a change to the outside of your house does is who the council is, whether a conservation area or a listing applies, and whether the place sits in a protected landscape.