SpecifiedBy Editornoun
- a small rectangular block typically made of fired or sun-dried clay, used in building.
verb
- block or enclose with a wall of bricks.
“the doors have been bricked up”
A Brief History
Bricks as we know them today have barely changed for many centuries. A basic form of brick was used as early as 7000BC in some parts of the world, though these were sun baked in order to harden them and not fired as they are today.
The Romans
The Romans were brilliant craftsmen and many of the bricks which they made to build their homes and public buildings are still perfectly viable today centuries later and continue to function as they were originally intended to.
They perfected brick making in the early days of their empire and it was used heavily in all construction. Because the Romans travelled so extensively, they brought their skills and knowledge along with them and local people were introduced to and taught techniques which would revolutionise building in Europe.
Travelling with mobile kilns, the Romans would create bricks wherever they wanted buildings and many were stamped with the marks of the particular legion who had overseen their creation, these can still be seen today in many of England’s older towns and cities.
Early Brick Making in the UK
Brick making as an industry in the UK didn’t really take off again until the Medieval era, although the use of bricks was not widespread until the Elizabethan period when the first of England’s grandest stately homes were being created.
Prior to the 13th and 14th centuries, brick was an unpopular building material and was considered to be inferior when compared to stone, even the Romans had commonly used stone within the fabric of their buildings, alternating a layer of stone with a layer of supporting bricks.
A shortage of suitable stone and usable timber in Eastern England however, gave rise to a surge in brick making and by the late 1400s, brick makers and brick layers were considered to be as important as their stone mason counterparts.
It was however, an expensive building material at this time because bricks were created individually and by hand. Most brick makers worked alone or with a partner, taking many months to make enough bricks for a house.
Bricks during the 14th and 15th century were not only created in basic forms but also in elaborate and decorative shapes. The patterns of laying were distinctive and it was commonplace to create designs within walls by introducing darker coloured bricks which had been over-burnt deliberately in order to create deep purple or slate colours.
By the 17th and early 18th century, bricks were at what may be considered a high point in their popularity. The production techniques of brick makers had improved as had knowledge of firing techniques and the colours of bricks were varied with reds, purples, greys and pinks being desirable until around the mid-1700s.
The mid-1800s heralded the popularity of more muted shades; subtlety had become desirable as people sought a more classical façade.
Modern Brick Making & Distribution
By the time the Victorian period was in full swing, bricks were being produced at a rate not seen before and demand was extremely high as towns were growing at an exponential rate never seen before.
Manufacturing was becoming more and more mechanised allowing for more buildings to be created and by this point, the most ordinary of homes were routinely made from bricks with many towns boasting their own, large brickworks where bricks could be manufactured and used locally.
Those smaller towns and villages, without a brickworks, could easily benefit from deliveries via canal barge.
As the railway networks in England began to grow ever more popular and financially viable in the mid-1800s, so the smaller brickworks began to fall out of favour. Larger companies were able to offer lower prices, so town councils and builders would look towards these companies for their bricks.
Manufacturing Methods
Today, bricks are manufactured using a variety of methods, each of which influences the final look and finish of the brick.
Extruded bricks are made by forcing the mixture through an opening in order to create bricks of uniform size.
Wire cut bricks are cut to size following extrusion; a wire is utilised in the cutting process and this method gives a distinct finish.
Moulded bricks are created in individual moulds.
Handmade bricks are hand finished in moulds without the use of high pressure machinery.
Types of Brick
We can broadly separate bricks into two groups, namely stock bricks which are the most traditional style and wire-cut extruded bricks which are pushed from a mould and “sliced” with wires, though into these two groups also come
Wire cut extruded bricks tend to be more uniform in shape and are more commonly used due to the ease of production which makes them more affordable.
Stock bricks are often considered to be more attractive due to their lack of uniformity, they are thought to add more character to a building though they are not hand made. Few manufacturers produce hand thrown bricks today though there are some companies still specialising in the craft.
Air Bricks
Air bricks are manufactured with holes in them to allow the flow of air under the floor of buildings that have suspended floors
Brick Slips
Also known as brick tiles, these are basically the face of a brick. Brick slips can be purpose made, or produced from a cutting of a full brick. As such, many bricks have a ‘brick slip’ option as well.
Concrete Bricks
These are a very basic brick and they are not fired but “chemically set”; sometimes they can be sourced with added details such as a pitched face. They are basically affordable and often utilised in areas which are not on show.
Engineering Bricks
Not pretty but tough and hard wearing; engineering bricks are often used for projects where appearance is not paramount, within tunnels or groundworks for example.
More detailed guide here.
Facing Bricks
Facing bricks are attractive to look at in addition to being hard wearing and so they are often used externally.
Fletton Bricks/London Bricks
These facing bricks are produced from Lower Oxford clay which when fired produces some interesting effects due to the presence of coal within the clay.
Glass Bricks
Also known as glass block, glass bricks are, as you may have guessed, made from glass. They provide an opportunity to allow some light through solid walls.
Handmade Bricks
Handmade bricks are moulded on a bench in a similar way to stock bricks but because the clay isn’t managed by machine, the bricks have a distinct pattern of creases on their faces which gives them a very individual look. They’re expensive to produce and so are usually used within high-end projects.
Paving Bricks
Also known as block paving or simply ‘pavers’, paving bricks are commonly used to create a decorative pavement area.
Salvaged Bricks
Popular due to their charm, it is still quite easy to source old bricks but they often require a lot of cleaning which can be labour intensive. Sometimes, unused old stock may be sourced.
Special Shaped Bricks
Not every building is designed in such a way that uniform bricks can be used. Special shaped bricks allow for unique and innovative designs to be created.
Stock Bricks
Stock bricks are moulded into shape in a less automated process and so they appear far more irregular which is a highly desirable element for many as the overall look they provide is less industrial and more heritage, making stock bricks the most suitable material for conservation areas.
Technical Properties of Bricks
- Alumina — 20%-30%
- Silica — 50%-60%
- Lime — 5%
- Magnesia — 5%
- Oxide of iron — Trace
Compressive Strength
In general, fired clay bricks offer a very high compressive strength; supporting high loads with ease, bricks are considered suitable for buildings of up to 4 floors in general though with suitable additions can also be used as load bearing walls in far taller buildings.
Porosity
Porosity is one of the most important features of brick, directly affecting its performance. The porosity of brick contributes to the transport of moisture within the bricks thanks to the “capillary” affect which allows moisture to be absorbed in the day and then released throughout the night.
It is this ‘breathing” capability which helps a building to retain its humidity levels and regulate temperature. This inherent absorbency though, can adversely affect a structure owing to its vulnerability to frost or chemicals which can be introduced from without.
The ideal level of porosity within bricks has been shown to be 8% as at this level, brick is 10 times more resistant to salt attack which can affect not only the aesthetics but also eventually, the surface area of bricks.
Achieving a balance of porosity in brick is vital to their continuing performance in terms of insulation and resistance to outside environmental factors and the perfect rate to ensure a good result for both.
Fire Resistance
Brick is very fire resistant. With a ratio of 100 mm brickwork combined with 12.5 mm plastering, bricks will resist the effects of fire for around 2 hours.
In general bricks can support heavy loads even under intense heat whilst concrete performs less than half as well on account of concrete’s propensity to lose moisture far more quickly.
Hardness
A slightly ambiguous term which refers to the compressive strength of a brick and the brick’s resistance to water in addition to its resistance to frost. It is accepted that in order to fulfil all of these requirements, a brick should be hard-burned.
Many professionals test the hardness of a brick by tapping it with a hammer. The sound emitted by a hard brick should be a “ringing” tone rather than a thud.
Brick Bonds
Running Bond
This is the most commonly used bond and was first seen to be used by the Romans; it features stretchers offset by on half of a brick per course.
Common Bond
Not the most common despite its name, this is nevertheless a popular bond and features a course of headers every 5 or 6 courses.
English Bond
Featuring alternating courses of stretchers and headers with a header being centred above a stretcher.
Flemish Bond
Alternating headers and stretchers for each course; each header is centred on a stretcher both above and below.
Stack Bond
This is for internal and non-load-bearing walls only. It features stretchers stacked on top of stretchers with aligned joints.
Much of the decision making process regarding bonds is down to personal preference though some, as in the stack bond, are not suitable for all applications and this needs to be considered.
Bond illustration copyright of Archtoolbox
Related Standards and Regulations
The previous British Standard Specification for clay bricks, BS 3921, has now been entirely replaced by a new European CEN Standard Specification for clay masonry units, BS EN 771–1.
This European Standard has now been published in the UK as one of the BS EN series of standards.
Similarly, clay paver products which were formerly Specification Standard BS 6677: Part 1 has now been replaced completely with BS EN 1344.
The CE mark is still to be considered as part of conformity within the EU’s requirements.
There are several references to masonry, including bricks, within the Building Regulations Approved Document A — Structure.
Further useful information about the standards & regulations which apply to bricks may be found at:
