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 in Swanage 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 in Swanage 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.

What 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.

The area of a wall tells you almost nothing until someone has looked at how far back the old mortar has failed.

Depth and method. Joints have to come back to sound mortar, well behind the face. Hand raking is slower than a disc, but a grinder widens the joint and knocks the arris off soft Purbeck stone and old brick, and once that edge is gone the wall never looks right again.

Matching the mortar. Too strong a mix is the classic mistake. Cement holds water in a soft stone, and the face blows off after a hard frost. On the town's older walls it is lime to the building lime standard, with the sand chosen to match the colour of what is there.

Access on the hills. A terrace that steps down towards the bay, a stone cottage on a narrow lane and a post-war bungalow need different set ups, and work at height rules decide when a scaffold goes up.

Replacement. Spalled bricks and decayed stones are cut out and replaced one by one, and that count moves the price more than the metres do.

Ask other quotes how deep they rake and with what, what mortar they use, and how many bricks or stones they have allowed to replace.

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 Swanage, the mix and the joint profile are part of what the listing protects, so the specification has to be agreed before work starts.

From our base in Boscombe to Swanage is 10 miles. We repoint across Swanage, Herston and Durlston and along the road to Langton Matravers and Corfe Castle, all of it Dorset Council. Bournemouth Roofing & Building Ltd is registered in England and Wales, and company number 15471719 lets you look us up. Before you book a visit in Swanage, you can read our customers' Google reviews, word for word, on our reviews page.

The business is Thomas Hannen's, and he is the person who comes out, checks the joints and prices the job. There is a verified 10 out of 10 from a customer on Checkatrade. Both the visit and the written quote, line by line, are free.

Most repairs in Swanage 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.