Glossary of Terminology




Aggregates can be coarse or fine. This is determined by whether the material passes through a sieve of a specified aperture size or whether the sieve retains them. Stone that has been broken up, gravels, sand and slag come into the category of aggregates. The term aggregate can also be a general term describing any quarried or dug material that has been through a grading process. 


Asphalt has become something of a generic description for all types of bituminous mixtures. This can include coated macadam and rolled asphalt. European Standards will refer to asphalt in many instances when British Standards refer to bituminous mixtures


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Building Information Modelling (BIM) is becoming an increasingly used design tool by architects, unlike older CAD design packages BIM includes product information which helps the designer see how a building will actually work in practice. The use of BIM in the design process also assists in reducing wastage on site during the construction phase as well as assisting the operation of the building once it is handed over to the facilities management team on completion.

If you want to keep right up to date why not click here and visit the National BIM Library?


Normally a black or brown viscous liquid or a solid material, bitumen has adhesive properties and is made up of crude oil-derived hydrocarbons found in natural asphalt.

Straight run bitumen - obtained after the final stage of distillation of crude oil of a suitable type. Normal grades used - 50 pen (hard) to 300 pen (soft).

Cut-back bitumen - bitumen whose viscosity has been reduced by the addition of a suitable volatile dilutant or flux. Normal grades used - 50, 100, 200 secs.

British Precast Concrete Federation

The British Precast Concrete Federation (BPCF) is the umbrella trade association for a wide range of construction products manufacturers - including concrete block and flag paving. As a body the BPCF works to represent the sector and also to help drive standards within the sector such as with the Sustainability Charter which members sign up to which will help to deliver enhanced sustainability across the construction sector. Find out more by clicking here.

Building Research Establishment

The Building Research Establishment (BRE) is an independent and impartial, research-based consultancy, testing and training organisation, offering expertise in every aspect of the built environment and associated industries. We help clients create better, safer and more sustainable products, buildings, communities and businesses - and we support the innovation needed to achieve this. Find out more by clicking here.


The Builing Research Establishment Environmental Assessment Method (BREEAM) sets the standard for best practice in sustainable building design, construction and operation and has become one of the most comprehensive and widely recognised measures of a building's environmental performance. It encourages designers, clients and others to think about low carbon and low impact design, minimising the energy demands created by a building before considering energy efficiency and low carbon technologies. Find out more by clicking here.


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This is a road construction material used below sub-base level – examples are top rock (crushed) and ready dug sand and gravels. These come into the category of low cost materials – others are sometimes used.

Carbon Footprint

Carbon Footprinting is one of many indicators which should be considered when looking at the sustainability credentials of a construction product. Like most members of the British Precast Concete Federation, Brett have signed up to the industry Sustainability Charter which commits members to ongoing reductions in Carbon usage.

However, it can be misleading to only look at Carbon to determine sustainability criteria as other criteria such as recycled content and waste disposal also need to be considered.

CE Marking

Since July 2013 it has been a mandatory requirement for construction products to be CE Marked before they can be placed on the market within the UK where a relevant European Standard exists to test against.

This allows specifiers to quickly compare the performance of one product against another similar one to ensure that they are looking at like for like materials. The vast majority of our products are covered by the following Standards:

- BS EN 1338: 2003 Concrete paving blocks.

- BS EN 1339: 2003 Concrete paving flags.

- BS EN 1340: 2003 Concrete kerb units.

- BS EN 1341: 2001 Slabs of natural stone for external paving.

- BS EN 1342: 2012 Setts of natural stone for external paving.

- BS EN 1343: 2012 Kerbs of natural stone for external paving.

If you need to obtain a Declaration of Performance for our products, please click here.


A compound of burnt lime, clays and shale, ground to a powder, which when mixed with water hardens fast. It is used as a binding agent in concrete and in mortar. In this application it typically makes up around 7% by volume which is why cement and concrete have widely divergent sustainability credentials.


These are crushed angular stone pieces of a single size material usually between 3 and 28mm – but can go up to 40mm. Crushed rock can be blended in with chippings in differing proportions and they lend themselves to a wide variety of applications.

Coated macadam

This is a material made of graded aggregate, coated with bitumen. The interlocked aggregate particles are responsible for the compacted road surface’s strength. Because strength of macadam is derived from mechanical interlock, crushed rock is the normal choice of aggregate

Code for Sustainable Homes

This is a national standard introduced by the Government to drive continuous improvement and innovation in the home building sector and increase the long term sustainability of the sector. The Code for Sustainable Homes provided a uniform environmental assessment method for rating and certifying the performance of new homes. The Code for Sustainable Homes was withdrawn by the Government in March 2015 although many of its elements were subsequently absorbed into the Building Regulations for new developments although it continues to operate for "legacy developments" in England and in Wales and Northern Ireland

Concrete aggregate

Aggregate used to produce concrete for various applications, pipes, blocks, panels and ready mix for example

Crushed rock

A mechanical crusher is used to break rock - part of the process of producing sized aggregate for asphalt production and comes in two main types of either hard or soft stone.

Cut-back bitumen

Cut-back bitumen - bitumen whose viscosity has been reduced by the addition of a suitable volatile dilutant or flux. Normal grades used - 50, 100, 200 secs.


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Dimension stone

These are large blocks of quarried stone, cut, shaped or carved. Having aesthetic qualities, Dimension stone is mostly used for architectural features and the external cladding of prestige buildings.


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Environmental Product Declaration (EPD)

The Environmental Product Declaration (EPD) is an independently verified and registered document designed to clearly communicate consistent information about the environmental impact of construction products across their life-cycle. This transparency allows designers to compare alternative materials and come up with the most environmentally sound solution for their project and is essential when looking at green public procurement (GPP) and building assessment schemes. Find out more by clicking here.

Ethical Trading

The Ethical Trading Initiative (ETI) is a leading alliance of companies, trade unions and NGOs that promotes respect for workers' rights around the globe. Brett Landscaping actively encourage their suppliers to adopt the ETI Base Code especially in areas of the World where the greatest risk is identified in our supply chains.

Brett Landscaping work closely with the TFT Responsible Stone Programme to help us best manage our ethical trading activities in the highest risk areas of our business. TFT work with some of the world’s largest importers to help protect workers across their global supply chains. Find out more by clicking here.

EN 1317-2 (N1)

EN 1317-2 is the recognised test standard for Road Restraint Systems. The N1 test consists of a 1500 kg passenger vehicle hitting the kerb at a speed of 80 kmh and at an angle of 20°. In order to pass the test, the vehicle must be safely redirected without passing over the line of the kerb thereby protecting pedestrians and other road users.

Our Trief GST2A kerb has been independently tested by the Transport Research Laboratory (TRL) against BS EN 1317-2 Road Restraint Systems, and proven to pass to containment level N1. Their Report (Reference No. TRL068) concluded that the Trief system fully complied with the acceptance criteria for the TB31 test with an ‘A’ rating for impact severity level.

The ‘A’ rating (out of A, B and C) is defined within the standard as affording a greater level of safety for the occupant of the errant vehicle than the other two classifications. Similarly, when it comes to protecting pedestrians and structures, the test report found that, during the entire test sequence, none of the wheels of the vehicle passed over or under the kerb.

See the test and view the full TRL report by clicking here.


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Granite is a very tough, naturally occurring igneous rock which can range in colour from dark greys through to reddish brown. Its hard wearing properties and classic texture makes it a firm favourite as a paving product where it can add style to a design. Much of the Granite used today is imported from outside the UK so it is worth checking that your supplier sources product ethically. Find out more about ethical trading initiatives, including a Base Code, by clicking here.

Granular Sub-base

This is a graded granular material that meets DoT Specification for Highway Works, Cl.803, Type 1 and Cl.804, Type 2. In limestone quarries where impact crushers are used, GSB can be manufactured as the product of one crusher with no treatment other than straightforward screening that removes any oversize pieces. In igneous rock quarries the product of more than one crusher is required to meet the specification, or the GSB is produced by blending single size chippings. Recycled materials can also meet this specification for use, such as Optimix (50% limestone and recycled concrete aggregate) and Opti-blend (100% recycled containing slag, asphalt and concrete).


Is a non-coherent natural mineral aggregate from natural disintegration of rock. It consists mainly of rounded pebbles for sub-angular rock fragments. It normally occurs in sand and gravel deposits or detritus.

Green Guide

The first edition of The Green Guide was launched in 1996 and aimed to provide a simple universal guide to the environmental impacts of building materials which was easy-to-use, based on numerical data and allowed the designer to compare different building products on a universal scale

The Green Guide today is used as a component in many sustainable design tools - but most frequently it is associated with BREEAM . Building products are graded from A+ through to E according to their environmental impact which helps the specification professional maximise the sustainability credentials of their project at the design stage.

The majority of concrete paving products will achieve a typical A+ / A rating depending on the type of product and the application. Find out more about using the Green Guide by clicking here.


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HAPAS accredited products

Products accredited with HAPAS certification means that the material, production and laying are all externally audited to give customers confidence in these schemes. To be accredited with a HAPAS certificate, a product scheme has to meet certain performance criteria over a two-year period


Important in the top surface of roads, Hardstone, such as granite, improves skid resistance and prevents rutting. This is a highly durable stone.


It is the clay in hoggin that holds the mixture together when compacted. Hoggin is frequently used on top of good quality sand and gravel, and it is often required to meet the Type 2 GSB specification with no further treatment. The clay constituent can be high for certain purposes. It is most often used in foundations and on minor roads.

Home Zones

One of the major developments in urban planning over recent years has been the move away from so called 'identi-kit' estates and a move towards creating more sustainable residential areas where the needs of pedestrians, cycles and children are given priority over the needs of motor vehicles. This involves the use of greater design at the planning stage to create shared spaces so that no one user group is dominant.

There have been a number of examples of successful Home Zone projects in the UK in recent years where the use of the concept has created stronger communities, reduced traffic speeds and created more desirable places to live. By creating integrated designs it is also possible to minimise operating costs as speed can be designed out thereby reducing the risk of accidents and the associated need to speed control measures. Find out more by clicking here.

Hot Rolled Asphalt

This is a less widely used material and is made from coarse aggregate and sand with bitumen. The strength partly comes from the interlocking aggregate particles, but mainly from the sand and very stiff bitumen around the aggregates.


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Interpave is the UK trade association for manufacturers of concrete paving products along with Interlay which represents the paving contractors. Today, Interpave plays a key role in providing technical information and helping to drive industry standards across the industry and promote best practice installation across all sectors.

In particular Interpave has played a key role in helping to drive standards for Sustainable Drainage Systems (SuDS) to help reduce the risk of urban flooding as urban sprawl continues to increase the areas of impermeable surfaces. Find out more by clicking here.

Iron Pyrites

Iron Pyrites is a naturally occurring sulfate of iron which can be found in mineral deposits - particularly gravels and aggregates. Occasionally these can find their way into concrete products and cause some localised surface staining. This does not in any way affect the performance of the product in service.


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Kiln Dried Sand

Kiln Dried Sand is silica sand which has been dried in a kiln to remove all the moisture before it is ready to use. It is an extremely fine, dry sand which enables it to flow easily into the joints and gaps in block paving.

Kiln Dried Sand has many applications but it is primarily used for the joint filling of block paving. This helps to prevent water ingress into the sub-base and stops the blocks moving or becoming loose - whilst allowing the surface to remain more flexible than many other surfacing materials.

If you pressure wash your drive it is essential to re-fill the joints once it has thoroughly dried out to prevent water ingress and sinking of the paving.

Note: Given that Kiln Dried Sand helps prevent water ingress it should not be used on with permeable paving where it will defeat the purpose of using permeable paving.


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A versatile sedimentary stone found in many areas of the World with great wear characteristics making it ideal for use in construction including use in asphalt. However, it is also makes a versatile and attractive flag paving stone where its colour range, which extends down to very dark greys, makes it a great choice. Take a look at our natural stone range to find out more about limestone flag paving. Much of the Limestone used today is imported from outside the UK so it is worth checking that your supplier sources product ethically. Find out more about ethical trading initiatives, including a Base Code, by clicking here.


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Manual for Streets 1 & 2

The Manual for Streets, first published in 2007, emphasised that streets should be places in which people want to live and spend time in, and are not just transport corridors. In particular, it aims to reduce the impact of vehicles on residential streets by asking practitioners to plan street design intelligently and proactively, and gives a high priority to the needs of pedestrians, cyclists and users of public transport

Manual for Streets 2 builds on the philosophies set out in Manual for Streets and demonstrates through guidance and case studies how they can be extended beyond residential streets to encompass both urban and rural situations

These two publications have had a significant effect on how we look at street design and integrating the needs of vehicles with the needs of pedestrians and residents in urban planning. Find out more by clicking here.

Marine aggregates

Sand and gravel won from the sea bed by dredging.

Modern Slavery

The modern business World has increasingly long and complex global supply chains where there are unfortunately opportunities for Modern Slavery to occur. This is especially prevalent in low pay - low skill jobs and can happen just as easily here in the UK as in a stone quarry in India.

The Brett Group take this issue very seriously and are pleased to publish our Modern Slavery and Human Trafficking Statement as required under section 54 of the Modern Slavery Act 2015. Please click here to view our current statement or here to find our more about the issue.


A mix of sand, cement and water used to bind together blocks, bricks and building stone in construction work.


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The soil and materials overlying the rock or sand and gravel to be extracted. It can be top rock or poorer quality material – this might be soft shale or clay. It may be sold as fill or soils which may be stored and used in the final restoration of the quarry


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Permeable Paving

One of the major innovations in block paving in recent years has been the development of permeable paving blocks which allow surface water to drain between the blocks and into a specially designed sub-bse where the water can then be held before leaving site. This innovation replicates natural drainage patterns and helps to reduce the risk of major flooding events as surface water runoff is delayed thereby preventing local drainage networks from being overwhelmed.

Permeable paving therefore provides a great way for designers to create effective Sustainable Drainage Systems (SuDS) as permeable paving also helps to reduce pollution and requires no additional land take making it increasingly popular with developers as it allows new land to be developed without an increased risk of flooding. Find out more about our range of permeable paving by clicking here.

Pesticides and Weed Control

This issue of effective weed control is a crucial one to keep any paving looking good and in great condition. The growth of weeds is one of the main causes of pavement degeneration and can generally be significantly reduced by regular sweeping to keep the paving clean thereby preventing silt deposits forming a base from which weeds can grow. If looking to use weedkillers or pesticides you need to be aware of the Govenment publication 'UK National Action Plan for the Sustainable Use of Pesticides (Plant Protection Products). You can download a copy here or by visiting their website:

Portland stone

This is a high quality dimension stone originating from the Isle of Portland in Dorset. It is a strong uniform stone (Jurassic oolite) without internal laminations.

Pre-cast concrete

Factory-moulded concrete structures that are transported to construction sites for use. Used for flooring, staircases, drainage pipes, water tanks and specialist kerbing.


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Quartzite is a naturally occurring metamorphic rock comprsed mainly of quartz. It comes in many different colours and provides an attractive, hard wearing paving flag ideal for patios. Take a look at our natural stone paving range to find out more. Much of the Quartzite used today is imported from outside the UK so it is worth checking that your supplier sources product ethically. Find out more about ethical trading initiatives, including a Base Code, by clicking here.

Quality Assurance Schemes

These are external monitoring schemes that continually check and confirm that material is being produced as stated within the companies Quality Manual. The external governing body awarded ISO 9001:2000 accreditations to companies that comply with national quality standards. This gives customers satisfaction in products produced under these schemes.


An open surface working, from which virgin rock is extracted.

Quarry fines

Crushed, broken hardstone that passes through the smallest screen or aperture (usually 5mm or 3.35mm).


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Railway ballast

This 50mm single sized aggregate must conform to a grading requirement the most significant of which is the Wet Attrition Test. The current specification requires a maximum Wet Attrition Value of 6 for high speed tracks therefore excluding most limestone.

Ready-mixed concrete

Sand, aggregates, cement and water mixed at a specialist plant or in a truck mixer then delivered to construction sites.

Ready-mixed screed

A semi-dry mixture of sand, cement, water, and in some cases proprietary additives produced at a specialist plant, then delivered to construction sites.

Recycled aggregates

Re-processed concrete, road surfacing, rock or bricks which have been removed from first use and crushed, screened and blended ready to be used again.

RIBA Plan of Works

The Royal Institure of British Architects (RIBA) first produced a Plan of Works to enable developers to work to a common development timeline back in 1963. This has been updated frequently since then to incorporate new developments within the construction environment.

The most recent update of the Plan of Works was in 2013; the current version along with more information can be viewed by visiting the RIBA website or by clicking here.

Run-of-quarry material

Large stones that have been blasted down from the quarry face and left untreated. Often used in dams, breakwaters and sea defences.


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The type of sand and its origin should be stated, e.g. river sand, dune sand, pit sand, etc. Sand is small mineral particles resulting from the natural disintegration of rock and it needs to be relatively free of silt and clay. In soil mechanics sand is a size (2mm-63um) and (4mm – 63um) for aggregate in concrete.


Sandstone is an incredibly popular stone choice for paving products. Its versatility to accept polished, textured, flamed or riven surfaces creates a huge range of potential aesthetics to suit almost any project - or pocket. Most of the sandstone paving is today imported from outside the UK so it is worth checking that your supplier sources product ethically. Find out more about ethical trading initiatives, including a Base Code, by clicking here.


A layer of material laid in situ, directly onto a base, bonded or unbonded, or onto an intermediate layer or insulation layer, for one or more of the following purposes: to obtain a defined level; to carry the final flooring. (Also see Ready-mixed Screed).

Screened aggregate

Sand, crushed rock and gravel that has been separated into various sizes by screening. Sand and gravel are usually produced to meet the requirements of BS EN 12620 (Aggregates from Natural Sources for Concrete) either as graded aggregates (40-5, 20-5, 14-5mm) or single sized (20/40, 10/20, 6.3/14, 4/10, 2/6.3mm). 3 fine aggregate gradings (C, M & F). Crushed rock produced in sizes to meet the requirements of BS EN 13043 for use in bituminous materials e.g. road surfacing, usually 20/31.5, 10/20, 6.3/14, 4/10, 2.6/3, mm and 3mm to dust.

Secondary aggregates

These are the waste products of other industrial processes that can be used to substitute natural aggregates. Examples include crushed glass, china clay waste, incinerator bottom ash and slag.

Self-compacting concrete

A concrete mix designed for use in confined areas where conventional compacting equipment cannot be used. Its main feature is that it can move easily through congested reinforcement steel and requires no vibration to achieve high strengths and durability.


Slate is a naturally occurring metamorphic rock that is both atrractive as well as highly durable. This makes it an ideal building material generally - but a great stone for use in paving. Take a look at our slate patio paving range to find out more. Much of the slate used today is imported from outside the UK so it is worth checking that your supplier sources product ethically. Find out more about ethical trading initiatives, including a Base Code, by clicking here.

Straight run bitumen

Straight run bitumen - obtained after the final stage of distillation of crude oil of a suitable type. Normal grades used - 50 pen (hard) to 300 pen (soft).

Surface course

To improve wear and skid resistance the top surface of a road has a wearing course. It is made of Hot Rolled asphalt or coated macadam and laid over the base course. It is made using high PSV stone to improve wear and skid resistance.


The vast majority of our concrete paving products offer the specifier a highly sustainable route to development; as a rule of thumb most will have a minimum of 7% recycled content, a BRE Green Guide rating of A+ / A - depending upon the type of sub-base used - and can be recycled at their end of life.

Given their exceptional durability and aesthetic qualities concrete block or flag paving is a great choice for the designer looking to develop sustainability. The ongoing risk of increased flooding events is also an area where block paving can help play a role in sustainable develpoment with the advent of permeable paving.

Locally sourced natural stone products, such as our commercial Yorkstone range, have a similarly high sustainability aspect which helps explain their ongoing popularity as the paving of choice for many of our urban spaces.


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Now little used for the production of coated materials because of environmental toxins, tar is a viscous liquid, black in colour with adhesive properties. It is obtained by the destructive distillation of wood, coal and shale.

Thin surfacing

Used in road surfacing to reduce noise, and also spray and skidding in wet weather.

Traffic loading guidance

Modular paving materials can be used to create a surface suitable for trafficking by a wide variety of loadings - albeit dependent upon the underlying pavement construction. As an approximate guide the following is suggested by Interpave:

  • All paving below 50mm is generally suitable for pedestrian traffic only.
  • 50mm paving is generally suitable for driveways, patios, pathways and footways.
  • 60/65mm paving is generally suitable for use on adopted highways and other roads <0.5 msa, cul-de-sacs, petrol forecourts and pedestrian areas subject to regular heavy traffic.
  • 80mm paving is generally suitable for most heavy duty pavements 0.5 to 12 msa.
  • 100mm paving is rarely used and is required for only the most demanding heavy duty pavement applications.
Transparency In Supply Chains

Following passage of the Modern Slavery legislation earlier this year the UK Government have published reporting guidelines for businesses on how they are managing the risk of modern slavery within their global supply chains. Please click here to view the guidance notes

Type 1

A granular material conforming to DoT specification, used in the lower layers of road construction; it is a mix of particles sized from 40mm to dust. When compacted it forms a solid base for roads and buildings. Type 1, which has to consist of crushed rock, slag or concrete, is the superior material and is the only one permitted for major trunk roads and motorways. Other sizes and blends are sometimes required to meet local requirements. Crusher run material from other types of crusher will meet the Type 1 and 2 BSB specifications with no further treatment (see under GSB).

If you want a handy tool to calculate how much Type 1 aggregate you will require please click here.


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Waterproof concrete

A mix of concrete which contains special additives which enable it to be used under water. It is used for bridge pier reinforcements, dock areas and for flood protection systems.


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Yorkstone is a tight grained sedimentary sandstone rock which takes its name from the quarries in the County of Yorkshire where it has been quarried since medieval times. The typical Yorkstone is a blue-grey / buff colour and provides a hard wearing paving stone ideally suited to the urban environment.

Today most 'new' Yorkstone does not come from these original quarries but refers instead to a generic appearance. It is therefore worth checking the source of these products and, if quarried outside the UK, ensuring that the product has been ethically sourced.


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