Caring for Your Brick Walls

Adapted from the website www.bricksandbrass.co.uk

To care for your brickwork, begin by understanding the types of brick you have.

History

Until the 18th century, most houses in what is now the United Kingdom were either made from stone or wood and clay. The latter type would use bricks for chimneys to reduce the risk of fire.

Little used in the UK before the 14th century, bricks rose in popularity when Flemish refugees brought bricks into East Anglia. Their use spread and by the late 18th century, yellow 'stocks' became common in London.

In the 18th century, bricks started to be used for all parts of smaller houses. A brick tax was introduced 1784 and increased in 1794 and 1803. This slowed the trend but after the tax was repealed in 1850 bricks were used almost universally outside the stone areas.

During the period of the tax, one alternative to wooden weatherboarding was the 'brick tile' or 'mathematical tile'; these were tiles in which the surface exposed below the tile in the course above was shaped like a brick.

During the 18th century, as well as being taxed, bricks were also less fashionable; stucco was used to simulate stonework. Stucco frontages ceased to be used in London in the 1850s, being replaced by brick as the desirable material.

By the late 19th century, red bricks were cheaper and could be used for the public side of houses, yellows being relegated to the rear. Using a mix of types of brick in the same wall reached its peak in the Victorian Gothic revival.

For much of this period, bricks were made locally; their colour was influenced by the clays and other materials used, and by the temperature at which they were fired. The coming of the railways meant that bricks could be distributed more widely and greater uniformity resulted.

The finest bricks are 'rubbed' or ground to fit tightly with little mortar. This could be imitated by staining the mortar to match the bricks, and then setting a line of 'putty' into a groove cut in the mortar as it sets. If you are looking for a new career, learn this 'tuck-pointing' technique as you will soon be wealthy!

Materials

Bricks were made from clay which had been puddled, ie squeezed and blended, until it was smooth and impurities had been removed. Other materials were mixed in, such as chalk or ash, and once moulded could be placed in sand when still damp. Shaping could be done with a mould, by extrusion through a wire mesh, or by carving.

The bricks were then baked in a clamp or kiln. A clamp is a stack of dried bricks, with faggots of brushwood inside, and coated with clay. The Hoffman kiln was introduced in 1858; this made continuous production possible and the bricks were uniform in shape and strength.

Until 1800, most bricks were red from the iron in the clay used. Palladian ideals led to the development of 'white' bricks, in which lime changed the brick to pale yellow, buff, or brown.

A whitish brick made from Gault clay was used widely in the south-east of England outside London. Brown bricks were made and used in the Thames valley. A silver-grey brick can be seen in south Oxfordshire, Berkshire and Hampshire. In the Vale of York, a dark brown brick was produced.

As red bricks were re-introduced from the 1870s, they were expensive and so the most basic houses still used only yellow bricks; more expensive houses used reds just for decoration such as over windows. As the cost declined further, the front elevation was built entirely in reds.

Other colours were produced by the addition of cobalt, manganese and sand. If the brick was baked in the hottest part of the clamp or kiln it would often be darker or change colour through vitrification. For example, if a red brick is fired at very high temperatures, a blue or blue-black brick results.

Types of Bricks

'Stock', 'brindle', 'diaper', 'faience', 'bond', 'gault', 'tuck-pointing', 'header', 'fletton'; the language of bricks gives the lie to any suggestion that bricks are simple. But to any of us in a brick-built house, some understanding can help us to care for them.

The types of brick used were:

Yellow Stock

London. These soft, porous bricks were made from clay close to London. They were baked over a bed of coke for 10 to 12 weeks.

The black flecks in the brick come from the ash mixed with the clay; this burns, firing the bricks internally.

Gault

South-east of England, particularly in Ipswich, Cambridgeshire, the Isle of Ely, Peterborough, Huntingdon, Bedfordshire, Maidstone, and the south coast. A whitish brick made from Gault and the adjacent Jurassic and Pleistocene clays in the south-east of England, coloured with chalk.

Staffordshire Blue

These dark, purple-blue bricks were burnt in a kiln at 1200 degrees Centigrade, making a very strong, dense and impervious brick.

They are often called 'engineering bricks'. They were made by 1832, but the coming of the canals made their more widespread use possible.

Accrington Bloods

Lancashire. These are a dense red brick.

Red Builder's

Now called 'Tudor Reds', these were a high quality, kiln-fired, sand-faced brick used as 'rubbers'.

Fletton

Made in the East Midlands from about 1900, a blotchy pink self-firing brick often used for internal walls. Flettons are pressed, in a mould.

Brindle

A brown-purple brick with a striped pattern.

Common Brick

A soft brick used for internal walls.

'Blues' were also used for decoration. This 'diaper work' pattern is on an 1880 house:

As well as the standard, regular brick, typically 8ž inches by 4 by 2ž, shaped bricks are used for cappings, window reveals and sills.

Terracotta

Terracotta is a mix of fine sand and pulverised brick or burnt clay. The moulded block was then dried and fired in a kiln. Much terracotta is unglazed and pervious. Sometimes the firing gave a hard, impervious, vitreous glaze. Full or matt-glazed terracotta is called 'faience', and achieved by adding a glaze or enamel. By the 1880's, new colours were available, in addition to the previous choices of red and buff.

Foundations

The foundations, or brick footings, were typically three brick lengths at the base; 680mm - i.e. 3 x 215mm (8.5 inches), stepped up to the wall. By 1890, poured concrete was often used, with the stepped footings on top.

Bonds

The bond of the brickwork in which the bricks are placed in a pattern of headers and stretchers gives the wall strength and stability.

Three types of bond, the patterns in which the bricks are laid, are shown below:

Stretcher bond is only suitable for a single skin; in a modern house the inner skin is typically made from blocks, fixed to the outer brick skin by metal ties. English bond was not popular in the Victorian period. So the common bond is Flemish, with the alternate header-stretcher pattern.

Bricks are 'glued' together with mortar; until the 1920s, this was usually just a mix of sharp sand and lime. This is porous, flexible and matches the typically soft bricks it was used with. Cement has gradually taken the place of lime; it is much harder and largely impervious to water. It suits modern bricks which are much harder.

Special Patterns

Bricks were often laid in various special patterns, as well in the standard bonds. For example:

string course; a long, horizontal course of a different brick, stone or stucco
hood mould; a rib of brick or stucco over the top and upper sides of a window or other opening (also called a 'label mould'
cornice; a special string course, or set of courses, at the top of an exterior wall, below the eaves or some other horizontal protrusion
coping; a capping of a non-absorbent brick or stone on top of a wall

Finishes

Walls were never painted.

However, roughcast and pebbledash finishes were common, particularly to cover cheaper bricks, and later for more decorative purposes. Roughcast is a mixture of shingle or crushed stone and sand mixed with a cement. To achieve a pebbledash finish, the wall is first coated with cement, and then pea shingle or some other fine stone chippings are thrown onto the soft cement.

Another treatment common, after the 1870s in Gothic and Arts and Crafts styles, is tile or slate-hanging.

In this section we summarise how to manage damp, cleaning walls, repointing, and bricks in newly built extensions.

Damp

In caring for your brick walls, the most important issue is damp. Old bricks 'work' by absorbing rain but must 'breathe' to let it out again. You do not help your wall by painting it or using a textured coating; moisture will still penetrate it but cannot then evaporate. Your wall will slowly become more and more damp. If you already have paint on a wall, it can be removed but this is costly and the long-term effects of the chemicals used are not fully understood. However, if you have a damp problem, removal is still the best solution. Sand-blasting and other abrasive methods are not safe for most brick walls; they damage the hard outer skin of the brick, allowing erosion of the softer core.

Make sure your gutters are working well; you do not want water pouring down the wall. Victorian houses usually have a damp-course of overlapping slates. Older houses may have no such protection but do not worry; 'rising damp' is a furiously disputed phenomenon. If bricks are piled in a bath of water, moisture will rise above the water-level but only for one or two courses. If floor joists are above this level, and the walls are breathing, then your walls will be fine.

Make sure that the lead flashing round the base of chimneys is in good condition. Ideally, you should have a porous ground surface at the base of walls; gravel is good but soil with plants will also stop the bottom of the wall from being saturated. The ground should slope away from the wall.

This section explains the problems you can have with damp and excessive humidity, and how to remedy them.

Note that condensation in the winter on single-glazed windows is normal and does not indicate excessive damp. Damp and humidity is not a 'problem' unless it is excessive and persists all year.

With older, brick-built houses, the walls are often porous; they can get damp. The rules for damp in the walls are:

minimise water reaching the walls (outside - good guttering etc, gravel at the footings to avoid splashing, inside - keep good ventilation)
maximise evaporation (outside - avoid wall paints and treatments, inside - avoid vinyl paints and papers)

For condensation the rules are:

ventilate - opening a window or adding a vent will reduce the amount of water vapour
insulate - reducing cooling will prevent water vapour from condensing
heat - increasing the temperature of a window, wall or room will prevent water vapour from condensing
use moisture-absorbing trays on window sills
Do not over-ventilate otherwise you will reduce the temperature and the remaining moisture will condense; the art is in achieving a balance.

Cleaning Walls

Bricks can be cleaned but this is rarely necessary; you would never strip all the layers of polish from your antique table; your house has a patina too and it is best preserved.

New brickwork sometimes exhibits a white coating as it dries; these are various harmless salts derived from the mortar and bricks. Simply brush them off.

Do not sand-blast brick walls as irreparable damage is likely. In sand-blasting (or grit-blasting), a stream of air carrying sand is directed against a wall at high pressure. This abrasive process does remove dirt but it also scrubs off the brick and mortar surfaces which are usually soft in old buildings. The surface is left pitted and the protective outer layer damaged.

Repointing

Re-pointing is often demanded by a building society. If the pointing just has a lime mortar, you are very lucky. Any loose mortar can be scraped out. Insist on the use of lime without any cement, and that the same style of joint is achieved. If the wall has already been re-pointed but with a cement-based mortar, it is best just to patch any failed areas with a lime mortar. If the corners of the bricks are flaking because the cement mix is too hard, then the pointing must be removed. Use a 'scutch', a special spiked chisel. With care, you can avoid major damage to the bricks. An angle grinder is often used but can cause serious damage. Match the pointing in the existing walls; avoid the modern 'weather-struck' joint. If you need tuck-pointing, you may have to settle for stained mortar with a flush joint.

Extensions

You may need to match your existing bricks if you are building an extension or changing the positions of doors and windows. Reclaimed bricks are fine if you can match the type, colour and quantity needed. Make sure you use a SALVO member. However it is often hard to find good quality bricks; you want them unpainted and with good, crisp corners. There are a few companies which make bricks using traditional techniques. Insist on lime (with sharp sand), rather than cement. In an extension, this should be used for the breeze blocks or modern house bricks used for the inner skin of a cavity wall. Try to match the bond; this will require half bricks for the headers.

Your bricks may look plain and rather dull but they are the canvas for all the period detail in your home; look after them.

Disclaimer:

Original version at the following link below. This article was submitted by a member of the public and is intended to promote balanced discussion. Feel free to comment on this article. The owner of Never Paint Again and its webmasters accept absolutely NO responsibility for the information provided here and we do not infer in any way that the text displayed here is authored or owned by us.

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www.bricksandbrass.co.uk/diyelem/extwalls/bricks/bricks.htm

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