What is repointing?
The strength and durability of brickwork depends heavily on the mortar (a combination of cement, lime and builders’ sand) that is pushed into the spaces between the bricks. The spaces are called joints, and the practice of filling them is known as pointing.
Over many years, mortar breaks down through weather erosion. Rain, snow, wind, hail and frost can wear away the mortar until it crumbles and falls out, exposing open joints and allowing dampness to enter the building. This is when the brickwork needs to be repointed.
Repointing a wall
1) Remove the old pointing
Old pointing must be raked out to a depth of about 12-15 mm; don’t be tempted simply to add new mortar to the old. Some of the old pointing may be difficult to dislodge, so you might need to use a club hammer with a cold chisel or a special plugging chisel; looser material will come away with a thin wooden lath. Brush out the joints with a stiff-bristle brush.
2) Preparing new mortar
Now prepare some ready mixed mortar, or mix your own using one part cement, one part lime, (if the brickwork is older handmade or soft bricks) and six parts builders’ sand. Before applying the mortar, spray the brickwork with water to prevent the bricks from absorbing too much moisture from the fresh mortar.
3) Apply the mortar
Shape small sausages of mortar on the back of a pointing trowel and push them firmly into the vertical joints, holding a board underneath to catch any mortar that falls. Then fill the horizontal joints. Take care not to smear the face of the brickwork with mortar, because it will stain.
4) Shaping the mortar
When the mortar is firm enough to retain a thumbprint, it is ready to be shaped. There are various shaping options, and any new pointing should match the style of the existing brickwork.
Flush joints are achieved by scraping the edge of a trowel over the mortar, bringing it flush with the paintwork. Finish off by stippling the joints with a soft bristle brush to expose the sand.
Concave joints (also known as rubbed joints) have a high level of water resistance and, being recessed, can emphasise the quality of the bricks. This style of joint is ideal for an old wall, where the bricks are more worn and not so crisp. For concave joints you will need a pointing iron – a tool designed specifically for this purpose. As with the application stage, work on the vertical joints first.
Weatherstruck joints, shaped in a sloping profile, are decorative and conducive to good drainage. Beginning with the verticals, use the edge of a pointing trowel to press the mortar into shape. When working on the horizontal joints, you will find that the mortar spills out at the base of the joint. Use a Frenchman (a tool with a narrow blade) to trim off excess mortar.
When the shaped pointing has almost hardened, give the brickwork a vigorous brush to remove any surplus mortar.
Repointing is a task that can be done by a reasonably competent DIYer, but to do it effectively and tidily can take a bit of time and a lot of patience! For a professional repointing service by experienced builders, get in touch.