Don’t underestimate the importance of pointing. When it comes to brickwork and stonework, the mortar can account for around 15 per cent of the overall surface area and has a huge overall impact on the quality of your wall.
Done badly, with poorly mixed mortar spread all over the brick itself, and/or if the mortar is too dominant, it can spoil even the best brick — done well, it can give an alluring texture and shadow to any elevation.
As the primary defence against water ingress, as well as having a vital structural role, mortar is a critical aspect of a home’s maintenance schedule and shouldn’t be ignored. When taking on older homes it should be high on the priority list — it can often be a source of leaks and damp in homes in need of wider renovation.
Given the requirement for working at heights repointing is usually a job that is outsourced to a professional. But how do you approach it?
What is Mortar?
Mortar is the substance that separates individual masonry units from one another — not, as many people believe, holds them together. It also fills any irregularities on the bedding faces of the bricks or blocks. Whether your home is built of brick, stone or concrete blocks, mortar will play an important part in your home’s construction.
Mortar is softer than your bricks and this is why at some point in the life of a building, it will begin to show signs of ageing due to the weathering. Believe it or not, you want this to happen — the alternative is that the mortar is harder than the bricks and that they take the brunt of weathering, eroding and meaning portions of wall need to be rebuilt, which can be an expensive and disruptive job.
Repointing is simply the task of renewing the outer portion of the mortar joint, and a good repointing job on your home should last up to 50 or 60 years.
When Should you Repoint a Wall?
If you can easily see open joints around the mortar bed, then it is time to think about repointing. This is a straightforward job and the materials required to carry it out are not expensive. On the downside, it is a fairly labour-intensive task, meaning the cost of employing a builder to do it for you may be considerable. You might also find it hard to pin down a tradesperson who will be willing to come out to do bits and bobs of repointing.
For this reason, many people choose to carry out repointing on a DIY basis, as and when the need arises. Obviously this requires scaffolding hire and a head for heights in most cases.
Which Mortar Should You Use?
A large range of textures and colours (from dark to light) can be achieved when mixing mortar. The majority of homes built up to and including the Victorian era used lime mortar.
The use of cement in repointing mixes does tend to be a bad thing (although it is still frequently done) causing decay to occur earlier than with lime mixes and damp more likely to raise its head. Cement mortars are harder, more brittle and less porous than lime and will weather slower than the bricks themselves.
Mortars containing cement tend to be more susceptible to salt and sulphate attack, while mortars containing only lime (putty or hydraulic) and sand are not vulnerable to this kind of damage. Lime mortars are more expensive than cement — but in the long run they can actually save money as putting right problems caused by inappropriate cement mixes can be costly.
DIY Wall Repointing: A Step-by-Step Guide
Tools and Materials Needed:
- Cement mixer
- Pointing trowel
- Mortar board
- Soft brush
- Wire brush
- White cement
1. Just a taste of the patched-in mess of face joints before the work starts. Not only is there a mixture of materials, but the profile of the pointing ranges from semi-recessed to plastered-on-top — not good. Inevitably with an older house, plants have been growing up against the walls and these have to be pinned back and then restrained before any work can start on the building. Repointing is a messy job so plastic sheets are laid over flower beds and areas of grass.
2. The old pointing is removed with a hammer and chisel, with particular care taken near the areas shown in the following four steps. Disturbing old mortar around windows can affect the way they fit (and open). The chisel is used on its own to chip out only the loose material.
3. If mortar gets pushed into this gap it can move the door frame and make the door hard to open and close. Loose mortar is raked out gently with a narrow chisel. Metal gutter brackets are prone to falling out if they are disturbed during the chopping-out phase. A lot of stone had already weathered away beneath this one, so the team were very careful. The power cable for outside lamps is often run inside the pointing. It was easy to spot on this job because the joint was a different colour in the course leading up to the lamp.
4. This is what is left after the old mortar has been removed. The edge of the stone is revealed all round and there is now a gap wide enough to take (and hold) the fresh mortar which will soon be applied to the wall.
5. Plenty of dust is left in the gaps between stones afterwards. This is brushed out before pointing begins.
6. To keep the colour of the mortar consistent for the whole job, the mix is carefully measured out. In this case, three buckets of yellow building sand, one bucket of lime and a quarter bucket of white cement. Each full bucket is levelled off at the top while the quarter-full bucket of white cement is measured off to a line drawn inside the bucket.
7. Repointing is generally done from the top of the wall downwards. However, the first half metre of a solid wall without a damp-proof course (as here) holds a lot of moisture so this section is done first — giving it more time to dry. The mortar is pushed in firmly, working from right to left.
8. Once two or three courses have been filled, the vertical joins between are filled too. Notice that the mortar is allowed to overlap all the joints and no attempt is made at this point to neaten it up. With the bottom half metre of the wall complete, the top section is started. Within five hours, a team of two complete this stage on this 24m2 wall. The mortar is left until nearly dry. How long the drying process takes depends on the weather and the position of the house in relation to the sun. In this case, the mortar is ready in just a couple of hours.
9. A wire brush is used to take off the excess mortar and leave a face joint that is just lower than the face of the wall. In other areas of the country, a deeper joint or one that is flush with the wall may be more appropriate. The wire brush also cleans up the stonework as it moves over the surface. You can see the finished pointing, and the cleaner stone, emerging in this picture.
10. A close-up of the finished job. With the face joints now clearly defining the stones, the wall not only looks great, it is now ready to shrug off the weather for years to come.
How to Get Repointing Right: Top Tips
- Using a narrow chisel around windows and doors minimises the risk of pushing loose pieces further in around the frames.
- The use of an angle grinder should really be avoided — it is easy to slip and damage the face of the brickwork or stone and is unnecessary with most traditional lime-based mortars.
- When you have a space large enough to take the new mortar, stop raking out and brush the joints down. Then give the joints a spray with water — this helps the new mortar dry out evenly. Wait for the water to dry off before beginning to repoint.
- Aim to replicate the colour, texture and durability of the existing mortar. Carefully measure each component of your mortar and make a note of the quantities used to ensure each bucket load matches the last.
- Begin from the top down (in order to keep any dust and water spray away from freshly repointed joints).
- A slightly open final texture tends to look more attractive than a very smooth one. An easy way to achieve this is to gently rub the filled joint with a stick or rubber, and then to softly brush it over before it dries.
- To avoid the new mortar drying out too quickly, spray the joints lightly with water from time to time.