Re-pointing work should be carried out only in favourable weather conditions – never in wet or frosty weather or when rain or a frost is expected.
After raking out the old mortar, and in readiness for re-pointing, all dust and debris must be removed from the joints with a brush. Any left behind will interfere with the ability of the new mortar to bond into the existing brickwork. To ensure good adhesion for the new mortar, dampen the raked-out joints with a wet brush or a fine water spray, making sure that both the edges of the bricks and the old mortar are damp. The wall must not be too wet or saturated as this would lead to mortar stains on the brickwork when applying the new mortar to the joints.
For small areas of brickwork, the brick trowel blade can be loaded with pointing mortar but for larger areas its is recommended to use a hand-hawk, which can hold more mortar.
Whichever tool is being used to hold the mortar, the back of a pointing trowel is used to flatten an area of the mortar with a ‘patting action’, to a thickness of around 10mm (the width of a mortar joint) and with a fairly straight edge at the front. Patting the mortar in this way also helps the mortar adhere to the brick trowel or hand-hawk.
The process of filling the joints with mortar has four distinct steps (see Fig 271): Always starts with bed joints followed by cross-joints. Work downwards from the top of the wall, concentrating on an area of approximately 1 square metre of walling at a time.
Fig. 271 Method of filling mortar joints during re-pointing.
1. Tilt the hand-hawk away from the wall and use the long inside edge of the pointing trowel blade to cut away a piece of mortar around 15mm thick (in other words, the raked-out depth to be filled) from the front of the flattened mortar. As part of the same movement, move the trowel towards the wall, while at the same time pulling the hawk away from the wall. There will now be a narrow strip of mortar on the edge of the trowel. The cutting action needs to be quick in order to ensure that the strip of mortar sticks to the back edge of the pointing trowel. When re-pointing cross-joints, the strip of mortar needs to be cut off at a length of around 65mm, to fit the height of the cross-joint and to avoid staining the brick above and below the cross-joint. Mortar that is cut off for bed joints can make use of the full length of the edge of the pointing trowel blade.
2. Keeping the trowel at an angle, move the mortar towards the joint to be filled.
3. Firmly push the mortar into the raked-out joint and, using a twisting action of the wrist, pull the mortar against the most convenient arris of the brickwork to one side (for cross-joints) or to the edge above or below (for bed joints), to ‘clean’ the back of the pointing trowel and to release the pointing mortar from it. Pull the pointing trowel away. (The choice of arris used for this purpose is not important – it will change numerous times during the course of the work and depends greatly on the left – or right-handedness of the bricklayer and whether he or she is working above head height or at low level.
4. To avoid staining the brickwork during re-pointing, keep the back of the pointing trowel clean by scraping it on the edge of the hand-hawk. With the empty pointing trowel, repeat the process to build up the correct amount of mortar in the joint.
When an area has been re-pointed, apply a joint finish to the new mortar; see Chapter 10.