Lime repointing on the old walls of Ashmore

Lime pointing on solid walls. An old wall here 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 covered for days rather than hours.

Undoing a cement repoint. This is the commonest job in the village and the most damaging thing done to its walls. 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. A stack up here 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 here 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.

No rate per square metre: the area tells you almost nothing until somebody has looked at what the joints are like.

Getting to it. A thatched cottage with a stack on the ridge, a flint and brick lane wall and an outbuilding up a farm track are three different set ups before a joint is opened. The work at height rules are why the scaffold is a priced line, not something absorbed into a rate.

The joints decide it, not the wall. How deep the joints have to come back, and whether the faces have already spalled, sets the hours far more than the area does.

Matching is the part that shows. Too strong a mix is the classic mistake, and one hard frost takes the face off soft brick. Lime is right on most pre-1919 walls here.

Comparing quotes? Ask how deep the joints are raked and by hand or by disc, what the mix is and whether it has been matched, and whether the scaffold is in the price. Two quotes for the same job are usually two different jobs.

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 two things: frost, which expands the water in the joint and turns the mortar to powder, and 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 here 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.

We cover Ashmore and the villages along the top of Cranborne Chase, out through Tollard Royal and Fontmell Magna, broadly the SP5 and SP7 lanes, 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 is the one who comes out to price the job, not a salesman. A verified customer's 10 out of 10 on Checkatrade. The visit and the written quote are both free.