CPD 05 2023: Brick circularity, sustainability and innovation

This CPD module, sponsored by Vandersanden, explores the innovations in brick manufacturing, with a focus on the material’s green credentials

A brief history

Bricks are, without doubt, one of the oldest known building materials. The earliest bricks discovered are estimated to be from 7,000 BC. Uncovered around the ancient city of Jericho in modern-day Turkey, they were probably made from mud clay and sundried in the open air.

It was the Romans who furthered the production process, opting to use bricks that were fired in a kiln rather than dried by the sun. With the introduction of mobile kilns, the Romans were successful in introducing kiln-fired bricks to the entire Roman Empire.

During the 12th century, bricks were reintroduced in Germany, which created the brick gothic period that became common in northern parts of Europe.

Before the Industrial Revolution in the 18th century, clay production was made up of small, seasonal enterprises – but manufacturing techniques became much more sophisticated.

Today, bricks are a commonly used material in the construction of buildings, with an industry that has invested in the development of manufacturing different types of bricks in all shapes, sizes and colours. With the advancement of modern machinery and sustainable practices, making bricks (alongside reusing and recycling them) has become far more productive and efficient than ever before.

Learning objectives

  • Awareness of the properties of clay brick
  • Knowledge of the process and innovations in brick manufacture
  • Understanding clay brick and its position as a sustainable material
  • Consideration for industry standards, fire safety, supply, management and handling

Why choose brick?

Clay brick is an extremely durable and frost-resistant material, and one that adds to the thermal mass of a building and has a lifespan in excess of 150 years.

The material is sourced from a natural and abundant resource and can be either reused or recycled. It provides not only a sustainable option but also a cost-efficient one in comparison with many other facade materials.

Hampton Court Palace is a great example of how durable brickwork can be. The Tudor part of Hampton Court dates back to the 1530s and includes the chimneys pictured below. The south front was designed by Sir Christopher Wren for King William and Queen Mary in the 1690s.

Hampton Court Palace dates back to the 1530s and demonstrates how durable brickwork is

Brick manufacture

The Brick Development Association has highlighted four key areas for how clay brick is building a sustainable future in the UK: brick manufacture, brick in construction, brick in use and end-of-life circularity.

Bricks are produced using clay extracted from the ground which is then mixed with water and other additives. The clay mixture is then formed into individual units and fired to high temperatures in a kiln.

Clay, the primary raw material for manufacturing brick, is mainly quarried. However, it is also taken as a by-product from earth-moving activities and infrastructure projects such as road-building.

Bricks are produced with clay extracted from the ground, which is mixed with water and other additives

Many brick manufacturers use renewable energy sources, such as solar and wind, at their manufacturing sites – as well as using collected rainwater where possible to supplement clean water used.

Heat recuperation is often used during the manufacturing process, whereby heat from the kiln is reused in driers where bricks are dried before firing.

Bricks require minimal packaging, and material savings can be made by using recycled plastic and minimising the quantity of ink used in labelling packs. Many brick manufacturers are also adopting the use of electric vehicles for their operations.

It is recommended to look for brick manufacturers that have environmental management systems in place and are ISO 14001 certified.

Bricks require minimal packaging, and material savings can be made by using recycled plastic

Reduced use of clay

A number of brick manufacturers are exploring ways of using less clay in the manufacturing process, while achieving the same appearance in clay brick on elevation.

In the UK, the standard metric format brick is 215mm long x 102.5mm deep. However, there are many different brick sizes available, creating a diversity of options in the overall appearance of the finished wall. The proportion of brick face to mortar also varies widely depending on the brick size and shape.

Many brick manufacturers are producing bricks in slimmer formats than 102.5mm on the bed face, the benefits being:

  • Less material is required, which saves material resources.
  • Less fuel is required, which saves energy consumed.
  • Slimmer bricks are just as strong and durable as standard format bricks.
  • The reduced thickness provides more space for insulation or to increase internal floor area.
  • Slimmer bricks are lighter, which makes them easier to handle on site.
  • Slimmer, lighter bricks mean a reduction in CO2 emissions from transportation.

Cut brick slips

Cut brick slips are an alternative method of using less material. Using machinery, a slip is cut from the face of every brick, resulting in a product that can be adhered to a wall or surface and provide the appearance of a brick facade.

A fantastic solution for finishing difficult structures such as ceilings, corbelling, or creative brickwork patterns, they are lightweight and thin, while at the same time a sustainable and robust material.

A stock brick can typically produce two brick slips, with the remainder able to be recycled by crushing and using the material as hardcore.

Whether for internal or external use, brick slips can be bonded onto many different substrates, including bonding straight onto insulated external walling systems by adhering the slips directly to the insulation.

The specification of a brick slip faced insulated external walling system allows existing buildings to be thermally upgraded without reducing existing internal floor area and without disturbance to the occupants of the building.

The RIBA Homes for Heroes publication describes the benefits of fabric-first and whole-house retrofit approaches, with the first being key to ensuring that energy efficiency works actually improve the energy efficiency of a property.

Brick slip faced insulated external walling systems improve the ability of a wall to withstand the elements, protecting the brickwork underneath and protecting against damp. They also help to prevent noise pollution inside the house and provide an opportunity to improve the external appearance of the house by covering existing imperfections.

Brick slips that are specially moulded and fired as slips, rather than cut down from whole bricks, require less material and less energy to produce than a full brick.

According to research data from Vandersanden, manufactured brick slips result in:

  • 70% reduction in consumption of raw materials
  • 50% reduction in energy consumption
  • No waste as surplus unfired clay is returned to the production process.

Reuse and recycling

The circular economy is a model of production and consumption, which involves sharing, leasing, reusing, repairing, refurbishing and recycling existing materials and products for as long as possible. In this way, the lifecycle of products is extended. In practice, it implies reducing waste to a minimum.

A Life Cycle Assessment (LCA) is a method of evaluating the environmental load of processes and products during their lifecycle. Considering the full lifecycle of a building can help ensure that all aspects are properly considered. In a full LCA, the energy and materials used, along with waste and pollutants produced as a consequence of a product or activity, are quantified.

With a significant proportion of waste from construction and demolition heading to landfill, minimising waste in construction is vital, which requires maximising the potential of building materials and components at the end of a building’s life.

The Brick Development Association’s Circular Economy Report states that clay bricks, if installed and maintained correctly, can have a service life in excess of 150 years.

Organisations such as the Ellen MacArthur Foundation, the UK Green Building Council and WRAP have published models for the circular economy in the built environment, which explain how buildings can be designed to facilitate circularity.

According to the Ellen MacArthur Foundation, key considerations are:

  • Design for material recovery
  • Design for reuse and refurbishment
  • Design for service
  • Design for longevity.

The key to recycling brick is determining whether the wall or building has been constructed using cement mortar or lime mortar. There is an increasing interest in constructing brickwork using traditional lime mortar because it is possible to deconstruct the brickwork, remove the lime mortar from the face of the bricks and reuse the bricks in a new construction.

Lime mortar can be removed with a heavy hammer and broad cold chisel for large lumps, and with a brick hammer for dislodging smaller pieces. Rubbing bricks on an abrasive grit stone is recommended where truing-up of surfaces is required, rather than the use of power tools and wire brushes.

An example of brickwork constructed in lime mortar is Tree House, in Ealing, west London, designed by Fletcher Crane Architects

With reclaimed bricks, a cautious approach is needed as there may be no evidence to prove the technical characteristics of the material – such as its compressive strength, frost resistance and water absorption. Tests may need to be carried out.

Cement mortar is difficult to remove from the face of bricks, and an evaluation should be carried out on whether sections of the brickwork as panels could be recycled. There will need to be a structural assessment and consideration given to the practicalities of storage and transport of the panels.

It is necessary to first establish whether the bricks are in a suitable condition for reuse. If the bricks are not in good condition (either chipped, cracked or showing signs of spalling) then they can be recycled by crushing down for use as in-filling material (hardcore).

Resource Rows is a project that reused brick panels from abandoned structures in a new building. It began with the Lendager Group evaluating the feasibility of salvaging sections of brickwork including the mortar joints bonding the bricks – assessing the disassembly method, storage and cost considerations. A structural assessment was carried out to evaluate the strength of the brick panels, and bricks were sorted based on brick type.

Resource Rows, by architect Lendager Group, reused panels of brickwork from the old Carlsberg brewery buildings in Copenhagen

Resources for designing sustainable buildings

There are a number of resources available to assist when designing sustainable buildings in brick.

The BRE Green Guide provides guidance on how to make the best environmental choices when selecting construction materials and components. Building materials and components are assessed in terms of their environmental impact across their entire lifecycle, with wall constructions in clay brick rated as A+.

The Brick Development Association has an environmental product declaration (EPD) covering bricks manufactured by their members in the UK – a document that may be used to quantifiably demonstrate the environmental performance of a product.

Designers can also refer to BS8895 Designing for Material Efficiency, as well as RIBA Plan of Work 2020 and RIBA Sustainable Outcomes Guide 2019, which provides tools to help RIBA members be leaders of sustainable outcomes. The guide also includes references and links to other publications such as the RIBA embodied and whole-life carbon assessment for architects and lists a number of sustainability calculation tools.

These documents provide a framework with actions, checks and outcomes, which can help project teams to take ownership of their buildings’ performance.

In terms of measuring the sustainable outcomes of projects, BIM makes it easier to complete sustainability processes and calculations, which involves setting out clear information requirements and then following a digital process to ensure that this information is delivered.

If you are researching the embodied energy and carbon of bricks, you may need to check with the manufacturer if the information is not available on its website. It is useful to know that there are standards for companies to follow when making green claims. Refer to ISO 14021:2016 Environmental Labels and Declarations for the specific requirements.

The future of brick

Various innovations are set to pave the way for brick manufacturing in the future. Some manufacturers have started producing bricks using sustainably extracted river clay, where locally available, with 20% recycled ceramic donor material – which has been broken down and ground in a sustainable way – then added to the river clay.

Some manufacturers are also exploring the use of hydrogen to fire bricks instead of gas.

At Heriot-Watt University in Edinburgh, bricks have been developed using 90% certified construction waste. The bricks are made in moulds and, instead of firing, a low-carbon manufacturing process is used (full details of the process are confidential).

At the University of Colorado in the US, researchers have developed a “living brick”, which is able to grow itself by drawing C02 from the atmosphere. The process involves gelatin and sand with bacteria added to a scaffold. Controlled light and humidity provide conditions for the material to grow and harden to create bricks. The bacterial growth process stops when the structure dries out, causing the cells to die.

Carbon-negative bricks are in development and are soon expected to be commercially available. The bricks are manufactured using the process of carbonation, combining CO2 and steel slag waste from stainless steel production. In the carbonation process, CO2 is absorbed rather than omitted. Calcium oxide (CaO) is present in steel slag, which is ground down to a particle size to optimise the carbonation process, combined with the moisture content of the raw material.

In a factory, two mixers mix raw materials (fillers and various slag sands) with a quantity of water. This water will be used to hydrate the existing calcium oxide (CaO) and to enable carbonation. The bricks are then shaped in a large press. The carbonation itself is done in an autoclave under high pressure and temperature, which makes it possible to manufacture bricks with strengths exceeding 100MPa.

The process uses green electricity rather than gas, and the carbon-negative bricks make use of waste products, providing permanent storage of a substantial quantity of CO2. Manufacturers are currently working together on carbon capture.

There are various innovations set to pave the way for brick manufacturing in the future

Regulations and fire safety

There are some important considerations when designing and building with brick, which apply to all brickwork construction to ensure its durability and long-lasting appearance.

Compliance and adherence to industry standards is essential when selecting bricks and any coatings being applied. All products must comply with the current standards as defined by the British Standards Institution (BSI).

The certification standards for clay bricks in the UK are:

  • BS EN 771-1:2011+A1:2015 – specification for clay masonry units
  • ECO standards ISO 14001: 2015

Recognised standards which must also be followed include:

  • BS 8000-3:2020 – Workmanship on building sites
  • Approved Document 7: Materials and workmanship
  • PD 6697:2019 – Recommendations for the design of masonry structures
  • PAS 70:2003 – Guide to appearance and site measured dimensions and tolerance

Clay brick is non-combustible and classed as A1 under the European classification system for reaction to fire set out in BS EN 13501-1:2018. The Grenfell Tower fire in 2017 led to significant changes to fire safety regulations, and it is vital that all those involved in the design and construction of buildings stay up to date on fire safety. A review of the RIBA’s safety resources is recommended.

The Building Regulations 2010, Approved Document B, Volume 1: Dwellings, Requirement B4 lays out the requirements for external fire spread, while Regulation 7(2) looks at access and facilities for the fire service. The June 2022 amendments to Approved Document B set out the requirements for residential buildings over 11m tall.

Management and handling

Designers have the responsibility when preparing or modifying designs to eliminate, reduce or control foreseeable risks that may arise during construction and during maintenance and use of a building once it is built.

Dry cutting of bricks should be avoided to reduce the amount of dust produced that may contain silica or quartz particulate, which causes silicosis. A suitable respirator or FFP3 standard mask should be worn. Ear defenders to protect from noise and safety goggles to protect from splinters or chips should be worn by those cutting bricks and those working in the vicinity of cutting. 

Bricks are dense, heavy and potentially dangerous if not managed and handled correctly on site. It is essential that health and safety best-practice standards are followed, and that these are considered during the whole process from ordering and delivery through to on-site management and build.

British Standard BS 8000-3:2020 Workmanship on building sites offers best-practice guidance when dealing with bricks, and most reputable manufacturers will have appropriate documentation and guidelines available. 

Clay brickwork is extremely durable and requires minimal maintenance. Periodic inspection as part of facilities management procedures is recommended to check whether repairs and maintenance are required, such as mortar joint repointing, unclogging of weep holes and removal of crawling vegetation. 

There may be a need to clean brickwork due to the effects of pollution in densely populated urban areas, accidents, poor maintenance and vandalism. Before carrying out any cleaning of brickwork, always refer to the manufacturer’s recommendations and consider the health, safety and environmental requirements.

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