RIBA Core Curriculum
- Design, construction and technology
- General Awareness
This course provides an overview of the modern brick manufacturing processes, the common terminology and the characteristics of different products. It covers topics such as brick technical properties, British Standards including BS EN 771-1, the influence of design and detailing on brickwork performance and the principles of brickwork movement, expansion joints and mortar specification.
In this section
- Examples of efflorescence and why it occurs
- Brick sizes and tolerances
- Different bond and alternative laying patterns
- Blending bricks to create mixed facades
- Examples and things to consider when using projecting bricks
- How to achieve curved brickwork and potential problems to be mindful of
The term efflorescence is associated with the formation of soluble salts on the surface of clay bricks.
Efflorescence should diminish naturally and eventually disappear but the weathering process can be accelerated through gently spraying walls to simulate rain, (a high pressure hose should not be used as this may cause further salts to be dislodged from bricks and mortar).
Alternatively to gently spraying, dry brushing of the deposit with a soft nylon brush may assist in the removal of salts.
The residue should be collected and removed so that it does not re-enter the brickwork at a lower level. A wire brush should not be used to avoid damaging the surface of bricks.
Chemical treatments such as cleaning acids are not recommended as they may exacerbate the problem and can cause damage to the masonry.
Nowadays most bricks in the UK are made to a standard brick size of 215mm long, 102.5mm wide and 65mm high (215 x 102.5 x 65mm) and laid with a nominal 10mm mortar joint. However, there is a growing trend towards more non-standard brick dimensions.
Brick sizes have an impact on a wide range of things like how the building is designed, the overall aesthetic appearance, the ease of laying the bricks etc.
Standard metric brick size adopted in 1970’s.
Imperial size bricks made in the late 19th/early 20th century were larger than modern bricks and are therefore still made for restoration purposes.
Brick size has become a key aesthetic choice in achieving an alternative look and feel. Demand is growing for formats that differ from standard UK dimensions.
From the moment the bricks are pressed into the mould, at the point at which they are dried and just before entering the kiln for their 3-5 day firing process they are oversized.
Millions of bricks are manufactured each year and there are only ever a handful of sizing complaints, very impressive considering the simple beginnings of each brick.
Size categories are based on formulae to take into account the different sized products across Europe. Size categories are based on formulae:
To determine the tolerance, measurements are taken for each of 10 bricks sampled randomly from the consignment against their length, width and height. The mean figure is then calculated.
Work Size T2 T1
Length 215mm +/- 4mm +/- 6mm
Width 102.5mm +/- 3mm +/- 4mm
Height 65mm +/- 2mm +/- 3mm
e.g. For a product of T2 tolerance, the mean figure for the length should fall between 211 and 219mm.
T2 = Extruded Products
T1 = Soft Mud Products
Tolerance category Tm and range category Rm allow manufacturers to apply additional deviation to individual products.
Although these could be tighter than the stated tabulated figures, it is most likely that these categories will only be applied to products with characteristic irregularities which require larger tolerance and range dimensions e.g. tumbled, Roman or handmade bricks.
A range category is also applied to determine the difference between the smallest and largest bricks within the sample of 10 units.
Work Size R2 R1
Length 215mm 4mm 9mm
Width 102.5mm 3mm 6mm
Height 65mm 2mm 5mm
e.g. For a product of R1 range, the difference in length between the smallest and largest bricks tested should not exceed 9mm.
The PAS 70 test would be carried out in the event of a dispute about sizes on-site to check the tolerance and range against the European Standard.
Given the millions of bricks that are sold each year, this is still a fairly rare test to carry out and none of the major brick manufacturers tend to suffer with sizing as a major issue.
Thinking about size tolerances when specifying a specific brick can be very important in terms of setting out or even the bond pattern you may wish to use so please contact the brick manufacturer for further guidance.
Whatever brick size is chosen for a project it is important to consider the brick size dimensions in the design stage in order to minimise cutting and potential problems on site.
The primary purpose of a bond is to ensure the brickwork is strong and stable, however bonds can also have a dramatic effect on the visual appearance of a wall.
There are a number of ways in which the stretcher (the longer, rectangular face) and the header (the shorter, square face) can be laid.
Let’s now take a closer look at some bonding patterns….
Cavity walls originated in late 19th century and insulation was introduced into the building envelope in the 1970’s. Because the outer leaf is now only half a brick thick stretcher bond has become the most common bond in use. (least number of bricks per m²).
Popular during the 18th century Header bond often employed contrasting brick colours to give a decorative effect. This bond produces a fine, tight wall, but uses so many bricks that it is usually reserved for very high-quality buildings. It’s also used for curved brickwork, as the short faces are easier to build into undulating shapes.
From the beginning of the 18th century, the Flemish bond superseded English bond. This style has stretchers and headers alternating within each course. Flemish bonds can be replicated in the half-brick outer leaf of a cavity wall by using whole bricks as stretchers, while the headers are created by half bricks called bats or snap-headers.
This is the oldest pattern, and was commonly used until the end of the 17th century. A course of stretchers alternates with a course of headers. English Bond is considered stronger than Flemish bond, so continues to be used for civil engineering projects, such as bridges, viaducts and embankments.
In stack bond the bricks do not overlap and therefore the arrangement is inherently weak. To compensate for the lack of bonding, typically bed-joint reinforcement is built into every third bed-joint.
Garden Wall Bonds
Laying stretchers uses up fewer bricks than laying headers however it is also less strong hence its use in traditional walled gardens and other modest structures.
Modern methods of construction allow for a creative use of bond patterns as facing brickwork is no longer a structural element.
The external envelope is now usually only a facing which pretends to be a solid load bearing wall.
This provides an opportunity to be creative and playful with brickwork design while at the same time maintaining the links to tradition, longevity and robustness for which brickwork has always been known.
The facade uses a mix of different brick colours: Castle Cream Blended Sovereign (three colours) and Original Blue Sovereign Stock (one laid every four horizontal and two vertical bricks).
Every two courses are stack bonded and alternately offset by half a brick length in between.
These various colours were chosen for a random laying pattern, with 50% turned, so that the backs faced out displaying imprints from the firing process.
Flemish bond was chosen as the background weave that can be modified by projecting and recessing the headers to add texture and pattern.
With all projecting brickwork some water will be held on the bed face on top of the projecting bricks for longer because the projection impedes water run-off.
There is an enhanced risk of staining over time which may require cleaning but projections within the brickwork will not increase the risk of frost failure.
Flemish bond with projecting headers creates visual interest on the façade.
Solid bricks may be required if there is a large projection otherwise the perforations or frog may be visible.
Consisting of ivory-coloured bricks, it resembles oversized lacework.
The perforated envelope in front of the closed exterior wall acts as a screen, projecting shimmering plays of light into the rooms during the day and glowing like a lantern at night.
The white perforated bricks with their distinctive configuration were specially made. They feature oval shaped holes at each end and are fixed with bars and steel cramps.
When the radius becomes too tight, joints will become overly tapered and the perpends will begin to overhang. Radial bricks are needed to form curved brickwork when the radius becomes too tight.
The Platinum White facing brick was chosen to help create a building that not only ties into the tonal range of the surrounding buildings, but more importantly create a building that provides a calming, therapeutic backdrop that does not distract and cause tensions to those visiting.
The use of a white brick gives a delicate contrast of light and shade throughout the day and also gives the building a sculptural quality. It also gives a sense of solidity, and in turn, protection from the external environment.
Subtlety is created by altering the bond used; for example, a stack bond is created between window openings and a stretcher bond is used for the majority of the walls which gives depth to the elevations.
You’ve reached the end of the CPD. To make sure you’ve taken on board the key learnings of this course, please fill out the quick multiple choice Q&A below. This will certify that you have completed the CPD and provide you with an email certificate, which, if the course is accredited, you can share with RIBA.