Repointing stone and brick walls in Owermoigne

One elevation, two materials. The old walls in the village core are solid wall construction, with no cavity anywhere in them, and they are rubble stone and soft handmade brick mixed in the same face, the brick usually saved for the quoins, the window reveals and the chimney. A wall like that has to stay breathable, because the only way it sheds the water it takes in is by evaporating it back out through its own surface. Stone and brick absorb water at different rates and dry at different rates, so a joint that suits one is rarely ideal for the other. The rule that gets you out of it is to match the softer of the two, because a mortar weaker than everything around it wears out first and can be renewed, while a mortar stronger than the brick moves the wear into the face of the brick where you cannot renew anything. So we point to the brick, not to the stone, and we use a lime with a coarse well graded sand so the wider joints between rubble do not shrink back as they cure.

Telling a tired wall from a failing one. Not every open joint is due. What we are looking for on the visit is mortar that has washed out behind the face of the material either side of it, mortar that is friable enough to come away under a thumbnail, and courses that sound hollow when you tap along them, which means the pointing has parted from the wall behind. Where those turn up together on the weather side, and there is penetrating damp showing on the inside face after a wet spell, the elevation is due. Where the joints are merely weathered and still hard behind the surface, it is not, and we will say so.

Undoing a cement repoint. This is most of what we do here. Hard cement over soft material stops the wall breathing and pushes the moisture out through the face, and once that starts the brick spalls and the stone loses its skin. Taking it out is slower than putting it in, because it has to come away without opening the joint any wider or disturbing what it is sitting against. The faces that have already gone are cut out and turned or replaced with reclaimed stock of the right size, held against the wall as a sample before anything is bedded.

Rake depth and finish on rubble work. On coursed brick you rake to about twice the joint width. On rubble stone the joints are irregular and the depth is judged as you go, back to material that is genuinely sound and no further. It all comes out by hand with a hacking iron and a plugging chisel, because a disc cutter or an angle grinder widens a joint permanently and takes the arris off soft brick in a single pass. The joints are damped down before filling so the wall does not pull the water out of the mix, and brushed back once the mortar has taken up rather than while it is still wet. The finish is kept slightly back from the face of the stones rather than smeared flush across them, which is the difference between a wall that reads as stone from the road and one that looks as though it has been rendered and then scored. On the brick, the joint goes back to whatever the wall already carries.

Plinths under cob. Several of the pre-1919 buildings here are cob standing on a period brick or rubble plinth, and that plinth is doing a real job: it keeps the earth wall clear of the splash line off the ground. When the plinth loses its mortar, water gets behind it and starts working on the cob above, which is a far more serious and far more expensive repair. Pointing a plinth is worth doing early and it wants the weakest, most open mix on the building, never a cement fillet at the base.

Stacks on thatched and tiled cottages. The stack is the most weathered brickwork on a cottage here, so it goes first: perished joints above the flashing, cracked flaunching and pots sitting loose. Repointing and re-flaunching is normally the whole job. Where the roof is thatched it changes how the access is set out, and we take that seriously, with sheeting over the coat and nothing that throws sparks anywhere near it.

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 rubble stone outbuilding up a farm track and a roadside wall on a narrow lane are three different set ups before a joint is opened. The work at height rules are why the scaffold is a priced line rather than 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.

The question that decides a repointing job in this village is which material you point to. On a wall of rubble stone with brick quoins and reveals you have two absorbencies and two strengths in the same face, and the mortar can only be matched to one of them. Match the stone, which is usually the harder of the two, and the mix ends up stronger than the brick beside it, at which point the brick starts doing the wearing instead of the joint. Match the brick and the mix is a little weaker than the stone, which costs you nothing, because a joint that wears is a joint you can renew.

So the practical advice on an old wall here is to ask whoever is quoting which material they have matched to and why. If the answer is that they have matched the colour, that is not an answer to the question. Ask for a sample panel that includes both the stone and the brick, and look at it after a few days rather than wet, because lime lightens a great deal as it dries and a panel judged on the morning it goes on tells you nothing. We put the panel somewhere sheltered and out of the way, and we would rather lose a week to that than get the mix wrong on a frontage that has to look right for the next thirty years.

We cover Owermoigne, Crossways, Warmwell and the DT2 villages between Dorchester and Wool, 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.