Brickwork: facelift for outside walls

Flakes of brick lying along the foot of a wall in winter are a sure sign of frost damage. The longer the problem is ignored the worse it will get, so as soon as the weather warms up apply a colourless, microporous water-repellent sealant, which will allow the bricks to breathe but will keep out moisture.

If you’re going to apply it with a spray gun , choose a still day, wear a respirator, and cover up to keep the fluid of your skin.

Treat the whole wall because the waterproofer can alter the colour of the bricks very slightly. Otherwise, the wall will look patchy, with treated areas being darker.

You can remove years of grime from bricks with nothing more elaborate than a stiff bristle brush and a running hose.

Work in horizontal bands from the top to the bottom of a wall, inspecting the pointing as you go. Use a solution of household ammonia—about half a cup in a bucket of water—on really grimy areas.

Wear goggles and rubber gloves to protect your eyes and hands.

Frost-damaged bricks should be replaced, but if you cannot find a matching one turn the damaged brick around. Use a power drill, on hammer action, and a masonry bit to make holes in the joint all around the brick to its full depth.

Chip away the remaining mortar with a plugging chisel, prise the brick out, then mortar it back into the hole, back to front.

A white powdery deposit, called efflorescence, is common on new brick walls. It is caused by salts in the bricks reacting with rainwater. Don’t try to wash it off or you will make the problem last longer. Instead, brush the affected area with a dry bristle brush until it stops recurring.

Think hard before you have the outside of your home sandblasted or cleaned with acidic chemicals. Although the results can look effective, both methods are harsh because they remove a layer from the surface of the walls.

Like a piece of old furniture that has been rubbed down and lost its patina, your house could lose some of its character if you try to make the old bricks look like new.

Remove stubborn stains like tar and oil with a paste made from fuller’s earth or ground chalk, mixed with paraffin or white spirit. Wipe over the stain with a little of the solvent used to make the paste, then spread a layer of paste over it.

Finally, tape a plastic bag or a piece of aluminium foil on top to stop the poultice drying out. Over a few days the paste will draw the stain out and you can wash the bricks clean.

A scrap of 6 mm or 9 mm external plywood makes a good mortarboard. Ideally, you want a piece about 400 x 400mm (16 x 16 in). Drill a hole for a screw in the centre of the piece and fix it to the end of a short length of broom handle.

Hold the board tight against the wall, directly below the joint being repointed. This minimises the amount of wet mortar getting on the face of the bricks or dropping on the ground.

Buy a bag of premixed mortar containing a plasticiser for a small area of repointing. Otherwise, it’s more economical to make your own; mix 1 part of ordinary Portland cement or masonry cement into 6 parts of clean building sand.

Add the recommended volume of a liquid mortar plasticiser or 1 part of hydrated lime if you’re using Portland cement (masonry cement contains a plasticiser). Don’t use washing-up liquid instead of lime or plasticiser, it is detrimental to the mortar.

Adding extra cement will make the pointing too hard, so that bricks absorb moisture more readily than the mortar, making them liable to frost damage. Adding extra water to a mix that is going dry will weaken it, although it is a good idea to flick a little water into the raked joints with a brush, to stop the mortar drying out before you can achieve a neat finish.

Bricklayers use a bladed tool called a frenchman to trim away wet mortar neatly from the base of weatherstruck joints. You can make one for yourself from a strip of thin metal. Bend about 25 mm (1 in) at one end over at an angle of 90º. Wear goggles in case the metal snaps.

Make a guide from a straight piece of 75 x 25 mm planed timber about 600 mm (2 ft) long to use with the frenchman. Pin two small pieces of hardboard or thin plywood on one side of the piece of wood, near the ends. These allow clearance for the tip of the frenchman between the guide and the wall.

Fıx a handle on the other side of the guide.

Traditionally, bricklayers used a short piece of metal bucket handle to ‘tool’ a bucket-handle joint. You can imitate the effect by dragging a short piece of hosepipe along the joint.

The way pointing is Ïnished is crucial to repelling rain.

Weatherstruck and bucket-handle joints are best, although flush joints often look best when you want to disguise small areas of new pointing.

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