From time to time brickwork may become dull and discoloured. This may be caused by grime and pollution, efflorescence, rust or accumulation of vegetable matter.
Dirt or pollution.
Bricks that are grime-laden and dull but otherwise in good condition usually require only simple treatment. Remove dirt with water and a stiff brush. If you suspect oily fumes have caused the grime, clean the surface with a solution of one part of household bleach to four parts of water. Lichen or mould can also be removed in this way. Stubborn areas may be scrubbed down with a wire brush. But take care not to damage the surface of the brickwork.
Efflorescence, caused by a chemical reaction within the bricks, shows as a white crystalline deposit on the surface. Remove as much as possible of the deposit with a stiff wire brush. Then wash the surface down with a solution of spirits of salts. Rinse afterwards with rain-water, not with tap water, as this may trigger off the chemical reaction all over again. Alternatively, two or three coats of a proprietary neutralising liquid can be applied to remove efflorescence. Brush it on, allowing a quarter of an hour between each coat for drying.
Rust staining can appear in brickwork joints or around ironwork embedded in brickwork, causing the brickwork to flake and crumble. Remove the mortar around the ironwork, clean up the metal and apply a rust inhibitor before re-mortaring.
Vegetable staining. First remove the plant, lichen or climber causing the trouble and brush down the surface of the brick wall with a stiff broom. Apply a liquid colourless antifungicide and allow it to dry.
Bricks may fail and no longer fulfil their waterproof function for a variety of reasons. Spelling occurs when porous bricks absorb water which freezes. As the ice expands, the brick crumbles or “spalls” at the edges. The defective bricks must be replaced.
Replacing a damaged brick. Depending on the degree of damage. Either remove the top layer of the brick and replace it or replace the entire brick. You will need a club hammer, bolster, narrow cold chisel, trowel, wire brush and protective goggles.
To remove and replace the top layer of a brick:
1. With the club hammer and bolster, cut back the brick surface until solid brick is reached.
2. With the wire brush clean out any loose material.
3. Cut a matching half brick (known as a queen closer) lengthwise with a club hammer and bolster to replace the damaged area. The replacement can be cut slightly under-size or the in-situ brick can be cut back a little further to allow a sufficient bed of mortar for the replacement brick to fit flush with the existing surface.
4. Apply a 1:3 mortar mix, with a little PVA additive, applied to both surfaces.
5. Repoint the joints when the brick has set.
To remove a complete brick:
1. Cut away the pointing, using a club hammer and cold chisel.
2. Dislodge the brick with the chisel. An awkward brick, which is firmly set, may have to be chopped out in sections.
3. Remortar the replacement and repoint.
Repointing. Once the joints between brick courses deteriorate, they must be re-pointed. The tools you need are a hawk for mortar, small trowel, Frenchman (a tool used to cut off excess mortar at the bottom of horizontal joints), plugging chisel, piece of sacking, brush, power drill with a routing attachment and, for a recessed joint, a curved piece of metal with a pointed end (a piece of metal bucket handle is suitable).
1. Lay down protective sheeting to catch mortar droppings.
2. Clear out joints on about a 3 ft 6 in square (say 1 m sq) area of the wall at a time. With the plugging chisel and hammer clean out the mortar to a depth of about in. (or 15 mm). Clear vertical joints first.
3. Brush down the wall, cleaning out any loose material.
4. Soak the joints to prevent suction of moisture from the new mortar when applied.
5. With the trowel, apply the replacement mortar. The new joints should match the old.
Recessed joints are used with rough-surfaced bricks. Place the mortar in the joint with the pointing trowel, using the inside bend of the bucket handle to “strike” the joint. Scrape in. (or 6 mm) of mortar from the vertical and horizontal joints. To ensure a waterproof joint, smooth the surface with a rounded piece of wood.