The damage
Heritage and traditional brickwork is a tricky beast. A traditional building is a building constructed before WW1 using solid walls and natural materials like clay, wood and lime. These Victorian walls, for example, are made with Lincolnshire bricks which are handmade, so not uniform in size or shape as modern bricks are. They will last hundreds of years if cared for correctly, but if they have been “restored” with modern materials, such as cement or concrete render, then their faces break, leaving them open to the elements, and they will often dry out and crack. You can see the damage from incorrect cement application in the middle picture. This wall was so bad that many bricks were loose, and we even found several birds’ nests inside! To repair this gable end, the top half had to be entirely rebuilt, selecting the best bricks and using others purchased from a reclaimed brickyard, but the bottom half was able to be repaired and repointed. In this blog, we’re going to walk you through it.
The correct materials for restoring brickwork
To restore brickwork such as this, it is essential to use a lime-based mortar, not cement. Lime allows the bricks to breathe, and it will withstand a certain amount of movement without cracking. The good news is, lime mortar is wetter, more flexible and in many ways easier to work with. The bad news is, it’s more expensive and it takes far longer to cure. Depending on the weather, your lime could still be soft after several days, or even weeks. You must lay on a dry day, yet, you must ensure the bricks themselves are not too dry. Lime mortar won’t stick to dry bricks. So, if it’s 25 degrees and sunny, mist your bricks with water regularly while repairing and repointing. If you need to know how to mix hydraulic lime, Mike Wye, who specialise in supplying heritage building materials, have an excellent guide here.
Preparation for restoring brickwork
It often takes longer to prepare the wall than to repair it. All the surfaces must be as clean and smooth as possible, with any loose materials removed. For us, this meant chipping away at all the cement that had been previously used to repoint the wall, with a pick-axe. Yes, it took ages. Yes, it hurt my back! For larger areas, it may be possible to grind old cement out, but this is not advisable because you can damage the bricks further.
You can identify which mortar shouldn’t be there by the colour. Lime mortar is lighter than cement. It is like white sand, and has a sandy texture. When you pick it, it is soft and will come away in grains.
By contrast, cement is grey and hard. When you pick it, it will (eventually) chip and come off in chunks.
This photo shows some of the original lime mortar on the far right, still in decent condition after 175 years, and the scruffier cement mortar that had been used to bulked the chimney (in the wrong bricks too!) and used to point over the top of the old bricks. All of this cement had to be removed (including the whole chimney, which we rebuilt.)
One you’ve chipped away all cement, check the whole wall for loose and damaged bricks. Remove any loose bricks by carefully chipping out the mortar surrounding them and easing them out. Small areas of “faceless” bricks can be left in and covered with lime, but where you have whole bricks that have lost their faces or cracked through, it’s best to remove them. They won’t last much longer.
Here, you can see there was a crack in the wall where movement had taken place following a failed lintel. Several bricks were loose and had to be removed. You can also see how the facing mortar has been chipped out from between the remaining bricks.
Replacing brickwork
Identify any loose bricks and damaged mortar and carefully chip it out to remove the brick.
Find a suitable brick the right size and shape for the recess. Lay a bed of mortar beneath it, slightly higher at the back, then place the brick inside.
To replace missing bricks, first clean out the recess. You need to chip away any mortar so you have a clean brick beneath.
Repoint all the way around the brick, pushing lime mortar into any of the gaps with a narrow trowel or your fingers. Ensure there are no air pockets.
Then use your fingers to ease out any loose mortar, and a blower or brush to remove the dust.
Once the lime has started to cure, you can smooth it off and brush it down as you would for repointing (see below).
Repointing brickwork
Begin by preparing the surface as detailed above, ensuring that all the recesses are free form dust by blowing or brushing it out. Unless there happens to have been a recent heavy rainfall, you will need to dampen the bricks with a spray mist of water to ensure the mortar “sticks”.
You will need a flat paddle, a trowel for scooping mortar from your bucket and a narrow trowel for applying mortar between bricks.
Deposit two/three scoops of mortar onto your paddle using the larger trowel. You will need to keep doing this regularly as you will use a lot.
Hold the paddle up to the surface of the brick and, using the narrow trowel, push mortar between the bricks repeatedly until there are no gaps. Keeping the paddle against the edges of the bricks should minimise the chance of mortar getting on the brick faces.
Identify bricks that have broken faces, such as this red one, or significant cracks. These faces will need to be covered with mortar to protect the brick from further perishing.
Apply the mortar with the trowel using movements in several directions. If it doesn’t stick, the brick is too dry and will need misting again. Don’t worry about it being too neat at this stage.
When you have applied mortar to the entire wall, the beginning should have started to cure – it will be harder and drier than when you applied it. Beginning at the place you started, rub a flat object along your mortar to remove rough edges.
You should aim for the wall to be as flat as possible to minimise weather damage. The misshaped bricks will be slightly proud of the mortar if you apply gentle pressure as you clean the mortar off.
Finally, brush off the wall with a fairly stiff, straw brush. Don’t brush too hard, just enough to clean off the brick faces without removing the mortar (it will still be soft.)
Restoring brickwork in this way will never look as “neat and today” as a rebuilt wall, but the wall will look considerably better than at the first, and will stand the weather again. As the mortar dries over the next few days, keep an eye on it. If you start to see cracks, it is drying too quickly, and you may need to mist it again and push in the cracks with your fingers. If you want to see more, you may be interested in reading about our restoration project on the even older stone wall on our property here.
