Repointing old Swanage walls in a matched mortar

Solid walls built in lime. Getting on for three in ten homes in Swanage predate 1919. Those are solid wall: no cavity, one thickness of masonry, shedding water by letting it evaporate back out through the joint. That only works while the mortar stays softer and more permeable than what it beds. We rake those joints by hand to roughly twice the joint width, perpends included, and point back in an NHL lime or lime putty mix gauged against a sample of the sound original for sand, colour and texture. The finish matches the profile the wall carries, usually flush or slightly recessed.

Stone walls, and why they are not brick. A good deal of the older fabric here is local stone rather than fired brick, laid in rough courses with wide, irregular joints. The principle is the same: the mortar has to be weaker than the stone, and it wants to be lime. The method differs. There is far more mortar in a rubble wall, the raking depth varies joint by joint, and the joint is struck back so rain runs off the stone.

Post-war outer skins. A third of the housing here went up between 1945 and 1982, and that is cavity work: a single skin of fired brick in a cement and sand mortar struck weather or bucket handle. It fails differently. The joint pits and opens at the arris rather than washing out, and once water stands in it a hard frost lifts the face off the brick. Matching mortar from that period means matching the sand and the gauge, not only the colour, so a trial panel goes up on a discreet part of the wall. Fresh mortar reads lighter than aged, so it is judged on how it will weather.

Blown faces, cut out rather than filled. Where a face has spalled we cut the brick out whole and turn or replace it against a sample held on the wall. Filling the hollow with mortar leaves a patch that never matches and drops out in two winters. Frost damage gathers under sills, beside downpipes and just above the damp proof course where a path has been laid up against the house.

Stacks, parapets and communal walls. Close to four in ten homes in Swanage are flats, many in converted houses still carrying a shared stack and a parapet. A stack takes weather on four sides with nothing warming it from inside, so its joints go friable years ahead of anything at ground level and the penetrating damp lands on a top floor ceiling. That is work at height. Where the wall belongs to a block, the freeholder instructs it.

Two things we will talk you out of. A water repellent painted over open joints traps what is already in the wall. And we will not point over movement: regular horizontal cracking every fifth or sixth course is corroding wall ties rather than tired mortar.

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

Getting to it. A three storey terrace running down towards the bay, a stone cottage in one of the old lanes and a post-war bungalow up on the hill are three different set ups. A chimney or a gable wants a scaffold, a boundary wall wants nothing at all, and how long the platform stands matters as much as how big it is. Access under the work at height rules is a priced line, not 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. Hand raking is slow, but a disc widens the joint and takes the arris off either side.

Matching is the part that shows. Too strong a mix is the classic mistake: cement holds water against a soft brick and the face blows off in the first hard frost. Lime is the right answer on most pre-1919 walls here.

Comparing quotes? Ask how deep the joints are raked and by hand or disc, what the mix is and whether it was matched, how many spalled bricks are being replaced, and whether the scaffold is in the price.

Swanage is unusually old for this stretch of Dorset. Nearly three in ten homes here were built before 1919 and the largest single slice of the town predates 1900 altogether, where a few miles inland the bulk of the housing is post-war. That decides the mix at the start. Put a dense cement mortar into a wall built in lime and the wall loses its route for getting rid of water, so moisture leaves through the brick or stone face and takes the face with it.

So settle the mortar first. Ask whoever is quoting what mix they intend and how they arrived at it, and be wary of an answer that is the same on an 1890s cottage as on a 1970s semi. If your address is one of the 129 listed entries in the town, the mix and the joint profile are part of what the listing protects, so the specification has to be agreed before work starts.

We cover Swanage, Herston and Durlston, and out along the coast road towards Langton Matravers and Corfe Castle, 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 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.