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.

• Water entering bricks and mortar may combine with soluble salts to form a solution. As the brickwork dries out this can migrate to the outer surface, forming a crystalline deposit as the water evaporates.
• This usually occurs following wet working conditions when the brickwork dries out for the first time.
• Protection of bricks and unfinished brickwork is of prime importance in preventing salts forming.
• Efflorescence is a temporary and harmless phenomenon and should be allowed to weather away naturally.

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.

Size Formats

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.

Size Formats

• Standard UK size 215 x 102.5 x 65mm
• 73mm bricks available for coursing in with old imperial 2 7/8 size bricks
• Imperial size 228 x 108 x 68mm
• European size formats – e.g. Waalformat (WF) 210 x 100 x 50
• Roman – from 440mm to 511mm long

Size Tolerances

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 Tolerances

• Clay is a natural material which is quarried, crushed, shaped and fired
• The European Standard BS EN 771-1 requires a manufacturer to declare a particular size category for each product based on individual brick measurements

Size Tolerances

• Different categories take into account the wide range of brick types and different manufacturing methods
• Tighter tolerances can often be achieved for more regular extruded or wirecut products than with handmade and stock bricks

Size Tolerances

Size categories are based on formulae to take into account the different sized products across Europe. Size categories are based on formulae:

• T2 = WS ± 0.25 Ö WS
• T1 = WS ± 0.40 Ö WS
• Tm = Manufacturer’s own specification

Size Ranges

• R2 = 0.3 Ö WS
• R1 = 0.6 Ö WS
• Rm = Manufacturer’s own specification

Tolerances Categories

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.

Tolerances Categories

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.

Tolerances Categories

Generally:

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.

Range Categories

A range category is also applied to determine the difference between the smallest and largest bricks within the sample of 10 units.

Range Categories

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.

On-Site Testing

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.

PAS 70

• Publicly Available Specification 70 (PAS 70) provides guidance on appearance of facing bricks and practical on-site testing methods for size.
• 10 bricks are selected at random. To determine the tolerance bricks are set out in a line on suitable level ground and the overall measurement taken.
• The overall dimension is then divided by 10 to provide the mean figure.

Setting Out

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.

Setting Out

• The size of the brick and the size of mortar joint chosen will have a big impact on the setting out of the brickwork.
• It is important that areas such as window and door openings, brick piers etc. are correctly planned out.

Setting Out

• Brickwork should be set out using the co-ordinating size e.g. 225mm (215mm work size + 10mm nominal joint).
• Generally every fourth or fifth perpend should be plumbed, with the joints between being evened out to give a consistent width, whilst also allowing for dimensional deviation in individual bricks.

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….

Stretcher Bond

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).

Header Bond

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.

Flemish Bond

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.

English Bond

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.

Stack Bond

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.

Alternative Patterns

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.

• Satisfactory curved brickwork can be achieved down to a radius of about 3.5m without the need for radial bricks in normal stretcher bond.
• Using header bond an acceptable appearance can be achieved for radii down to 2.5m.

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.

• Faceting around the curve means that perpend joints will begin to overhang the stretcher below as the radius reduces…
• Radial bricks are used 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.