Repairing damaged pointing in brick walls is an important maintenance job that should never be neglected. Repointing can also greatly improve the look of your brickwork, but needs doing carefully if it’s to look uniform.
T he mortar joint visible between the bricks on the face of a wall is called ‘pointing’ and its most important function is to provide a smooth finish thai prevents rainwater from seeping in behind the weather-resistant face of the bricks. If this happens during frosty weather, the water could freeze and expand, possibly cracking off the outer face of the bricks. In some cases defective pointing can allow water to penetrate the wall completely, appearing as damp patches inside. So it’s important that it’s in good condition if it’s to do its job properly.
When the wall was originally built the joints may have been ‘struck’ out of the bedding mortar as the bricks were laid – a process the bricklayer refers to as ‘jointing’. Or the bedding mortar may have been scraped out before it completely set, usually to a depth of about 15mm (5/ain), and then the joints will have been filled with fresh mortar and shaped – true ‘pointing’. Jointing is more durable than pointing because there is no break in the morlar between the bricks. However, either can fail in the end, so for simplicity’s sake we’ll refer to both as pointing.
If pointing starts to crack or crumble, it needs repointing – a job that involves chipping out the old mortar and replacing it with new. At the same time, the cause of failure should be traced and eliminated.
Complete repointing of a wall is only necessary if the damage is extensive. It is a big job to undertake and on any building other than a bungalow you’ll need fixed access equipment – scaffolding or a platform tower. Repointing does tidy up the appearance of the building as well as thoroughly protecting the brickwork, but if the damage is restricted to small patches you should be able to make a neat repair if you take care in matching the mortar colour.
If you intend to paint your outside walls, full repointing in flush pointing is desirable, but if the pointing is fairly new or fault-free you can get away with a little patching up. However, if you intend to give the brickwork an all-over mortar finish (whether rendering or pebbledashing), just scrape out the joints and clean them with a brush to provide a key for the render. Getting up to the job
You may be able to reach the area you’re repointing without access equipment. For small-scale repairs higher up the wall you’ll need steps or a ladder, but if you are tackling large areas or whole walls you need something more secure so that you have the full use of both hands and somewhere to put tools and materials.
For single storey buildings you can use decorators’ trestles and staging, which can be hired – though these may not be tall enough to reach a gable end. The best solution is to hire or borrow an access tower, which will allow you to work on much larger areas of wall in complete safety; full scaffolding, such as a builder would put up for a large-scale repointing job, is likely to be too expensive to hire for the length of time you would need to repoint an entire wall on your own. Access towers are much more flexible. They can be put up and taken down easily and, on level sites, can even be moved along on castors without the need for dismantling.
Experimenting with colour
If you are completely repointing a wall you may want to colour the mortar; if you are patching small areas you will need to try and match the colour of existing pointing so that the patches don’t show up. Different coloured sands give a range of mortar colours and your builders’ merchant can tell you what is available. Cement colouring can also be bought and added to the mix – it is usually combined with a plasticiser and is available in black, brown, green, yellow, red and orange.
You should experiment with any colouring before doing the whole job. If you are trying to match mortars you won’t know if you’ve got it right until the pointing is fairly dry. If you can, it’s best to leave a sample for a couple of weeks before going on. Likewise special colours will be a different shade when they have thoroughly dried out.
TOOLS FOR REPOINTING
Club hammer and 12mm (Vain) cold chisel: to chip out old pointing. A pointing chisel with angled tip is better still. Pointing trowel: like a brick trowel but only 125mm (5in) to 175mm (7in) long. Hawk: for carrying the mortar (a bucket is easier to carry when you’re up a ladder). TOOLS YOU CAN MAKE
Hawk: by nailing a 150mm (6in) length of broom handle or 25mm (1 in) diameter dowel to a 200mm (8in) sq piece of exterior grade plywood 19mm (3/tin) thick. Frenchman: for weatherstruck pointing. Clamp an old table knife in a vice and heat the blade with a blow-torch; bend the top 12mm (1/2in) of the blade into a right angle with a hammer.
Pointing rule: used with the frenchman to trim off excess mortar and shape weatherstruck pointing. Make from planed timber 50 x 10mm (2 x 3/ain), 1 m (3ft) long with parallel long side edges. Screw on two square blocks 25 x 25 x 10mm (1 x 1 x 3/ain) as shown with countersunk screws.
– dry-mixed for small jobs, obtainable in bags ready to mix with water. Buy a mix labelled ‘sand/cement’ or ‘rendering’ mix. Usually grey in colour when dry.
– for larger jobs mix cement and soft (bricklaying) sand in the ratio of 1:6 and add a plasticiser to make the mix more workable and frost-resistant.
– take care when using coloured mortar for pointing; you may get patchy results unless you are meticulous in measuring out quantities of pigment.
FINDING THE FAULT
Defective pointing could be due to:.
– incorrect original mortar mix.
– mortar-attacking chemicals in the atmosphere or rainwater
– leaking gutters and downpipes discharging onto the wall over a long period of time a failed damp-proof course.
Method of working
Unless the area to be repointed is very small, have a trial run first to practise the technique. Chip and rake out the mortar to a depth of about 15mm (5/sin) from a few joints, mix up a small amount of mortar and try to repoint. If you make a mess, scrape out the mortar before it sets and start again. When you are confident of your technique, you’re ready to tackle the whole job.
Whether you are treating the whole wall or only part of it, start raking out the old pointing at the top left-hand side and work across and downwards (reverse the procedure if you’re left-handed). Work on no more than 2 sq metres (21 sq ft) at a time. Be careful not to damage the edges of the brickwork and keep the groove square. At the same time scrub any moss or lichen from the surface of the bricks with a stiff bristle brush. Brush out the joints thoroughly to remove all old mortar fragments and dust. If any bricks need replacing chip them out carefully at this stage. Try to get a used brick replacement of the same colour from a local builders’ merchant so that the repair doesn’t look too obvious.
The amount of mortar you mix up depends on how quickly you can work – in average conditions a mortar mix is workable for a couple of hours. Roughly speaking you will need 2 V2 bucketfuls for 1 sq metre of wall -allowing for wastage and provided that you are filling to a depth of about 15mm (5/sin).
Try to get a workable but stiff consistency. Drag the edge of a trowel across it; this should leave ‘wrinkles’ if the consistency is dry enough.
Dampen the joints with an old brush and clean water, which should prevent the bricks from absorbing water too quickly from the mortar and reducing its strength. Transfer some mortar to your hawk, pick up a small sausage on the back of a trowel and transfer it to the first joint, pressing it in firmly to fill the gap completely. Start off by filling in all of the vertical joints (perpends) in your working area and then go on to the horizontals (bed joints).
It is easy to splash the wall below your working area with mortar, which may be difficult to get off especially if your mix is too wet. Hang a polythene sheet or an old linen sheet the wall below, with long battens to prop it in place. If the bricks do get spattered don’t try to wipe off the mortar with water as this makes a worse mess – leave it to dry and then brush it down with a stiff-bristled brush.
There are a number of different pointing finishes to be done when you’ve filled the joints in the area on which you’re working. You’ll obviously want to match the existing finish on a small repair job, but you have a free choice if you are completely repointing a wall. For exposed exterior walls weather-struck joints are best as they are angled to throw rainwater off very effectively. Rounded (or concave) joints are quite common and can be made with a length of plastic piping, while struck and recessed joints show very little mortar and give the brickwork an interesting shadowy appearance-this is not the most protective of pointing and is not recommended on exposed walls. Flush joints are used where the edges of the bricks are damaged and crumbly or where the surface of the wall is to be decorated later on with paint or rendered.
Pointing and brickwork that is badly cracked in clearly-defined runs across the face of the wall could be caused by:.
– structural movement due to ‘heave’ or subsidence in the wall foundations
– vibration from heavy traffic on a nearby road.
Such damage should be inspected by a builder or surveyor.
Chimneys needing repointing may also be suffering from serious structural defects and if not in use should be demolished by a builder.
Joints are the weakest point of the wall structure. If in doubt about the condition of your brickwork, consult an architect or builder but don’t try to patch up the damage.
REPAIRS TO BRICKWORK
If only two or three bricks in part of the wall are damaged:
– chop out the mortar joints round each damaged brick using a bolster chisel and club hammer, and lift out the brick (you may have to break it)
– mortar-in sound and matching replacement bricks and point to match the rest of the wall.
TIP: WHEN TO REPOINT
Frost will damage your new pointing and very hot weather will cause the surrounding bricks to dry out, however much you soak them, sucking moisture from the mortar and weakening it. Work on a mild, dry day.
TIP: PROTECT THE BRICKWORK
Mortar splashed on bricks is hard to remove without leaving a stain. Hang a polythene or old linen sheet on the wall below your working area, propped up with wooden battens, to protect the surface.
TIP: REMOVING MORTAR
If mortar gets on the faces of the bricks:.
– don’t try to wash it off with water as this makes a worse stain
– leave it to dry, then brush it off with a stiff-bristled brush.