Complete 2026 reference guide for UK aggregate grading: sieve analysis, BS EN standards, Type 1 MOT sub-base ranges, concrete aggregate sizes, recycled aggregate notes and downloadable grading tables.
What Is Aggregate Grading?
Aggregate gradingis the particle size distribution of an aggregate sample, normally shown as the percentage by mass passing a sequence of test sieves. In practical UK construction, grading tells you whether a material is suitable for concrete, mortar, asphalt, drainage, sub-base, pipe bedding, screed, railway ballast or general fill. A well-graded material contains a controlled spread of coarse, medium and fine particles. The smaller particles fill some of the voids between larger particles, improving compactability, stiffness and economy. A single-sized material, by contrast, has a narrower band of particle sizes and may drain well but compact differently.
For concrete, grading affects water demand, workability, finish, pumpability, bleeding, segregation and cement efficiency. For unbound sub-base, grading affects compaction, interlock, stiffness, permeability and resistance to rutting. For mortar and screed, grading affects cohesion, shrinkage and surface finish. That is why aggregate certificates, supplier declarations and sieve analysis reports are critical on commercial projects. A delivery ticket saying “20mm aggregate” is useful, but a grading report shows whether the actual particle distribution meets the specification.
Practical 2026 Rule
Do not choose aggregates by name alone. “Type 1”, “sharp sand”, “20mm stone”, “MOT”, “ballast” and “recycled aggregate” can vary between suppliers. Always check the grading envelope, fines content, aggregate standard, declaration of performance and any project-specific clause before ordering large quantities.
PSD / Sieve Analysis
Particle size distribution is produced by washing and dry sieving a representative sample through standard sieves, then working out percentage passing each aperture.
d/D Designation
European aggregate notation uses lower and upper sieve sizes, such as 0/4 sand, 4/20 coarse aggregate, 0/31.5 Type 1 or 0/40 Type 3.
Compliance Envelope
A grading envelope gives minimum and maximum percentages passing key sieves. A sample normally must sit inside the envelope to be acceptable.
Why Grading Matters on Site
Aggregate grading is not just a laboratory detail. It changes how material behaves under a roller, inside a concrete mixer, below a paving slab or in a drainage trench. Too many fines can make a sub-base water-sensitive and difficult to drain. Too few fines can make a close-graded material unstable because particles do not lock together properly. Oversize particles can cause poor layer thickness control or surface irregularities. A badly gap-graded concrete aggregate can create harsh mixes, honeycombing and high cement demand. A sand with too much silt or clay can increase shrinkage, reduce bond and create weak mortar or screed.
For small domestic jobs, a competent supplier’s certified product is usually enough. For structural concrete, highways, drainage systems and commercial slabs, you should record the specification, delivery source, certificate date and test standard. On projects with strict quality control, aggregate grading may be checked at regular intervals because quarries, recycled aggregate plants and stockpiles can vary over time.
UK Aggregate Standards for 2026
UK aggregate specifications are built around European/British Standards, project specifications and national guidance documents. The exact standard depends on the end use. Concrete aggregates are not specified in the same way as asphalt aggregate, mortar sand, railway ballast or unbound sub-base. The list below gives the standards and guidance most commonly referenced in UK construction documents in 2026.
- Standard / Guidance: BS EN 933-1; Primary Use: Testing geometrical properties; What It Controls: Particle size distribution by sieving; Practical 2026 Note: Use for PSD reports and grading compliance checks.
- Standard / Guidance: BS EN 12620 + PD 6682-1; Primary Use: Aggregates for concrete; What It Controls: Aggregate sizes, grading, fines, shape, quality, physical properties; Practical 2026 Note: Used with BS 8500 and BS EN 206 concrete specification.
- Standard / Guidance: BS EN 13242 + PD 6682-6; Primary Use: Unbound / hydraulically bound materials; What It Controls: Aggregate properties for civil engineering and road construction; Practical 2026 Note: Often combined with MCHW Series 800 for highways work.
- Standard / Guidance: BS EN 13043 + PD 6682-2; Primary Use: Asphalt and surface treatments; What It Controls: Aggregate for bituminous mixtures and trafficked surfaces; Practical 2026 Note: Check PSV, abrasion and polishing requirements separately.
- Standard / Guidance: BS EN 13139 + PD 6682-3; Primary Use: Mortar aggregate; What It Controls: Mortar sand grading and quality; Practical 2026 Note: Building sand for mortar is not a substitute for concrete sharp sand.
- Standard / Guidance: MCHW Series 800; Primary Use: Highway works; What It Controls: Type 1, Type 2, Type 3, Category B and other mixtures; Practical 2026 Note: Always check current contract documents and regional amendments.
BS 882 Is Historic, Not the Main 2026 Specification
Many older UK guides still mention BS 882 for concrete aggregate grading. It is useful for understanding legacy specifications, but modern UK concrete aggregate specification should be based on BS EN 12620, PD 6682-1, BS EN 206 and BS 8500 where applicable. If a drawing, bill of quantities or older specification cites BS 882, ask the designer or engineer to confirm the intended current equivalent.
Official and Industry Reference Links
Useful pages for confirming current standards and guidance includeBSI Knowledge for BS EN 933-1,BSI Knowledge for BS EN 12620,The Concrete Centre aggregate guidance,The Concrete Society standards summary,Mineral Products Association aggregate standardsandStandards for Highwaysfor MCHW documents.
Aggregate Grading Tables — UK 2026 Reference
The tables below are practical reference ranges for common UK material descriptions. Project specifications can be tighter, so use these tables as a starting point and then check the contract documents, supplier declaration and test certificate. Percent passing means the mass of material smaller than a stated sieve aperture, expressed as a percentage of the total dry sample mass.
Common UK Aggregate Size Designations
- Designation: 0/2; Common UK Name: Fine sand; Typical Use: Mortar, render, some fine bedding uses; Important Check: Clay/silt and organic contamination
- Designation: 0/4; Common UK Name: Sharp sand / grit sand; Typical Use: Concrete sand, screed, slab bedding, paving mortar; Important Check: Fines content and particle shape
- Designation: 4/10; Common UK Name: 10mm stone; Typical Use: Thin concrete, drainage, pipe bedding; Important Check: Cleanliness and suitability for intended layer
- Designation: 4/20; Common UK Name: 20mm coarse aggregate; Typical Use: General concrete coarse aggregate; Important Check: Particle shape, grading and water absorption
- Designation: 10/20; Common UK Name: Single-size drainage stone; Typical Use: Drainage trenches, soakaways, permeable layers; Important Check: Low fines and permeability
- Designation: 0/20; Common UK Name: All-in ballast; Typical Use: Small concrete works where permitted; Important Check: Batch consistency; not always acceptable for structural mixes
- Designation: 0/31.5; Common UK Name: Type 1 sub-base; Typical Use: Roads, footways, patios, driveways, slabs; Important Check: Fines range, compaction and certificate
- Designation: 0/40; Common UK Name: Type 3 open graded; Typical Use: Permeable sub-base / SuDS layers; Important Check: Free-draining grading and low fines
Type 1 Unbound Mixture — Practical Grading Envelope
Type 1 is one of the most widely specified UK sub-base materials. In highways-style specifications it is commonly treated as a close-graded 0/31.5 unbound mixture. Domestic suppliers often sell “MOT Type 1”, “Type 1 limestone”, “Type 1 granite” or “Type 1 recycled”. For load-bearing work, the important point is not the name on the bag: it is the grading and quality declaration.
- Sieve Size: 63 mm; Typical Overall % Passing: 100; Practical Site Note: No oversize above 63 mm
- Sieve Size: 31.5 mm; Typical Overall % Passing: 75–99; Practical Site Note: Controls top size for 0/31.5 material
- Sieve Size: 16 mm; Typical Overall % Passing: 43–81; Practical Site Note: Mid-coarse fraction for interlock
- Sieve Size: 8 mm; Typical Overall % Passing: 23–66; Practical Site Note: Controls overall grading shape
- Sieve Size: 4 mm; Typical Overall % Passing: 12–53; Practical Site Note: Boundary between fine and coarse behaviour
- Sieve Size: 2 mm; Typical Overall % Passing: 6–42; Practical Site Note: Sand fraction affects compactability
- Sieve Size: 1 mm; Typical Overall % Passing: 3–32; Practical Site Note: Fine sand fraction
- Sieve Size: 0.063 mm; Typical Overall % Passing: 0–9; Practical Site Note: Fines; too much can reduce drainage and stability
Type 3 Open Graded Sub-base — SuDS and Permeable Work
Type 3 is used where drainage performance is important, such as permeable paving sub-bases. It is more open graded than Type 1 and usually carries a lower fines limit. For permeable pavement, the bedding layer, geotextile, sub-base and discharge route all matter. Simply choosing an open-graded aggregate is not enough if the layer is contaminated by fines or compacted with unsuitable moisture.
- Sieve Size: 80 mm; Typical Overall % Passing: 100; Supplier Declared Range Example: —; Why It Matters: Maximum particle control
- Sieve Size: 40 mm; Typical Overall % Passing: 80–99; Supplier Declared Range Example: —; Why It Matters: Controls 0/40 grading
- Sieve Size: 20 mm; Typical Overall % Passing: 50–78; Supplier Declared Range Example: 58–70; Why It Matters: Coarse skeleton
- Sieve Size: 10 mm; Typical Overall % Passing: 31–60; Supplier Declared Range Example: 39–51; Why It Matters: Void structure
- Sieve Size: 4 mm; Typical Overall % Passing: 18–46; Supplier Declared Range Example: 26–38; Why It Matters: Fine aggregate limit
- Sieve Size: 2 mm; Typical Overall % Passing: 10–35; Supplier Declared Range Example: 17–28; Why It Matters: Permeability and stability
- Sieve Size: 1 mm; Typical Overall % Passing: 6–26; Supplier Declared Range Example: 11–21; Why It Matters: Fine sand fraction
- Sieve Size: 0.500 mm; Typical Overall % Passing: 0–20; Supplier Declared Range Example: 5–15; Why It Matters: Very fine sand control
- Sieve Size: 0.063 mm; Typical Overall % Passing: 0–5; Supplier Declared Range Example: —; Why It Matters: Critical low-fines check
Reading a PSD Report Correctly
Check the sample date, source, product name, test method, sieve sizes, percentage passing and specification envelope. Then confirm that results are monotonic: percent passing should not increase as sieve size gets smaller. A report with a high 0.063mm value may still look acceptable visually but can behave poorly in wet conditions.
Aggregate Grading QA, Testing and Common Problems
Good grading control starts before the aggregate reaches site. The buyer should specify the correct product, the supplier should provide evidence of conformity, and the site team should prevent contamination, segregation and excessive moisture variation. Poor aggregate management can turn a compliant material into a non-compliant layer before compaction or batching even starts.
Delivery Checks
Check delivery ticket, product name, source, date, load size and certificate reference. Reject obvious contamination or oversize material before tipping.
Stockpile Control
Keep different aggregate sizes apart, avoid mud contamination, manage runoff and minimise repeated handling that causes segregation.
Moisture Control
Moisture changes effective batching mass, compaction behaviour and workability. Wet fines can make a material look cohesive but perform poorly.
Common Aggregate Grading Problems
Excess finesare one of the most common issues. In concrete, excess fines can increase water demand and shrinkage. In sub-base, fines can reduce permeability and increase frost or pumping risk when water is present.Too little fine fractioncan make a close-graded material difficult to compact because there are not enough smaller particles to lock the skeleton.Oversize particlescan create weak spots in thin layers and may stop a layer being compacted to the specified thickness.Segregationoccurs when larger particles roll to the edge of a stockpile or delivery area, leaving a different grading at the top, bottom or side of the pile.
Recycled aggregates need extra care because their composition can vary more than primary crushed rock. Recycled concrete aggregate can be excellent when properly processed and certified, but site teams should check for asphalt, brick, wood, gypsum, glass, plastic and metal contamination. For highway and structural uses, recycled aggregate acceptance is usually controlled by clause limits and test reports, not visual inspection alone.
Do Not Use the Wrong Aggregate Just Because It Is Cheaper
Using building sand instead of sharp sand, drainage stone instead of compactable Type 1, or a high-fines recycled fill where a certified sub-base is required can lead to settlement, weak concrete, failed paving, blocked drainage and expensive remedial work. The saving on material is usually tiny compared with the cost of removal and replacement.
2026 Site Checklist for Aggregate Grading
- Confirm the material is specified byend use, not only by a trade nickname.
- Ask for thecurrent certificateand confirm the test date is relevant to the production period.
- Compare each sieve result against thecorrect grading envelope.
- Checkfines content, especially for drainage, SuDS and frost-sensitive work.
- Confirm the aggregate is not contaminated with mud, organic matter, gypsum, timber, plastic or deleterious material.
- Store stockpiles separately and avoid driving plant through clean aggregate.
- Record non-conformities and obtain engineer approval before using borderline material.
Aggregate Grading by Application — Concrete, Sub-base, Drainage and Mortar
Aggregate grading should always be matched to the job the material has to perform. A dense concrete mix, a permeable sub-base and a mortar sand can all contain mineral aggregate, but the ideal particle size distribution is completely different. Choosing the right grading improves performance and also controls cost because the aggregate skeleton reduces unnecessary binder demand. In concrete, the aggregate forms most of the volume, so a poor combined grading can force the mix designer to add more water, cement or admixture just to achieve workability. In unbound layers, the grading determines how the layer compacts and whether it remains stable under loading.
Concrete Aggregate Grading
For concrete, the goal is usually a stable combined grading of fine and coarse aggregate. The fine aggregate fills voids and improves cohesion; the coarse aggregate provides volume and strength with lower paste demand. A typical small site concrete may use sharp sand plus 10mm or 20mm coarse aggregate, while ready-mixed concrete suppliers optimise several aggregate fractions at the batching plant. The best grading depends on the concrete grade, slump, placement method, reinforcement spacing, pump requirements and finish. A 20mm coarse aggregate is common for general concrete, but it may be too large for thin toppings, heavily reinforced beams, kerbs, posts or detailed formwork. In those cases, 10mm aggregate or a designed pump mix may be more appropriate.
When reviewing a concrete aggregate certificate, look beyond the grading curve. Shape, water absorption, density, chloride content, sulfate content, freeze-thaw resistance and resistance to fragmentation can matter depending on exposure class and structural use. Recycled aggregate can be used in some concrete applications, but the permitted percentage, quality class and exposure limitations should be confirmed by the concrete specification and engineer. For structural concrete in the UK, aggregate selection connects directly to BS EN 12620, BS EN 206 and BS 8500. The aggregate grading page should therefore be treated as a practical interpretation resource rather than a full concrete specification.
Sub-base and Road Formation Aggregate
Sub-base aggregate is selected for compaction, load spreading and durability. Type 1 is popular because its broad distribution of particle sizes can compact into a strong, dense layer. It is used under roads, industrial slabs, yards, driveways, footways, patios and some foundations where a competent compacted layer is required. However, Type 1 is not automatically free draining. It contains fines, and those fines are part of its compactability. Where water storage or rapid drainage is required, an open graded product such as Type 3 may be more suitable. The engineering design should consider subgrade strength, traffic, layer thickness, frost susceptibility, geotextile separation, drainage falls and compaction method.
A common failure on domestic projects is laying a thin layer of Type 1 over soft ground without adequate excavation, separation or compaction. Even if the aggregate grading is correct, the finished pavement may rut or settle if the subgrade is weak or the layer thickness is inadequate. Another common failure is using a cheap recycled fill as a substitute for certified Type 1. Recycled materials can be excellent, but they need the correct processing, grading and contamination control. If the material is described only as “hardcore”, it may not meet any recognised grading specification.
Drainage Aggregate and Permeable Paving
Drainage aggregate normally requires low fines and an open structure. Clean 10/20 or 20/40 stone is often used in soakaways, land drains, French drains and granular drainage layers. For permeable paving, the whole build-up must be designed as a system: surface blocks or porous asphalt, jointing aggregate, bedding aggregate, sub-base aggregate, geotextile, subgrade and discharge arrangement. Adding too many fines, cutting slabs on top of the sub-base, stockpiling muddy material nearby or allowing soil to migrate into the voids can destroy permeability. A grading certificate is therefore only one part of drainage performance. Clean handling and installation are equally important.
Type 3 open graded aggregate is often used where a structural sub-base also needs to store and move water. It differs from Type 1 because the fines content is lower and the grading is more open. If a project is intended to meet SuDS requirements, ask for the designed void ratio, permeability assumptions and any maintenance guidance. For critical drainage works, permeability testing and a civil engineer’s detail may be required.
Mortar, Screed and Bedding Sands
Sand grading is especially important in mortar, render and screed. Soft building sand is usually rounded and fine enough for workable mortar, but it is not the same as sharp sand. Sharp sand or grit sand is more angular and better suited to screed, paving bedding and concrete. Using the wrong sand can change workability, shrinkage, finish and strength. A mortar sand with too much clay can make a mix sticky at first, but it may shrink, crack or lose strength as it dries. A screed sand that is too coarse or poorly graded can create a harsh finish and make compaction more difficult.
For floor screeds, aggregate grading should be consistent because the screed thickness, compaction, drying and surface finish depend on the sand skeleton. Where underfloor heating is present, where a thin bonded screed is specified, or where a resilient floor finish is being installed, the screed manufacturer’s grading and mix requirements should be followed closely. Do not assume that any bag labelled “sharp sand” will produce the same performance.
Worked Example: Checking a Type 1 Delivery
Suppose a site receives a 20-tonne load described as Type 1. The delivery ticket is checked against the order, and the supplier provides a PSD report. The report shows 100% passing 63mm, 91% passing 31.5mm, 67% passing 16mm, 43% passing 8mm, 28% passing 4mm, 18% passing 2mm, 12% passing 1mm and 5% passing 0.063mm. When compared with the common Type 1 envelope, each value sits inside the typical range. The site team should still check moisture, contamination, segregation, compaction thickness and layer preparation. Passing the grading check does not prove the layer has been compacted correctly; it only confirms the delivered material’s particle size distribution is consistent with the target grading.
If the same delivery showed 14% passing 0.063mm, the material would be too fine for the typical Type 1 guidance envelope. On a wet site, that could increase the risk of pumping, reduced drainage and poor performance. The correct action would be to quarantine the delivery, ask the supplier for clarification, and obtain engineer approval before use. If the project specification has a strict fines limit, the material may need to be rejected even if it looks acceptable by eye.
Best Practice for 2026 Specifications
Write aggregate orders using the standard, designation, source, grading category and intended use. For example, specify “certified Type 1 0/31.5 unbound mixture with current PSD certificate” rather than simply ordering “hardcore”. Clear wording reduces disputes and makes it easier for site teams to check deliveries.
Standards First, Supplier Name Second
Aggregate descriptions vary across the UK. For professional projects, specify the intended standard and grading category first, then the material source. CheckStandards for Highways,BSI Knowledgeand the engineer’s specification before procurement.
Aggregate Grading UK — Frequently Asked Questions
Common questions about sieve analysis, Type 1, Type 3, concrete aggregate, standards and downloads.
Aggregate grading means the distribution of particle sizes in an aggregate sample. It is usually reported as the percentage by mass passing each sieve in a standard sieve stack. A grading report tells you whether the aggregate is well graded, open graded, single sized, too fine, too coarse or outside the required specification.
BS EN 933-1is the main UK/European method for determining particle size distribution by washing and dry sieving. It is used for type testing, dispute resolution and checking compliance against grading requirements. Supplier production control may use correlated methods, but certified grading reports should clearly state the test method used.
Type 1 is commonly a 0/31.5 unbound mixture. A practical envelope includes 100% passing 63mm, 75–99% passing 31.5mm, 43–81% passing 16mm, 23–66% passing 8mm, 12–53% passing 4mm, 6–42% passing 2mm, 3–32% passing 1mm and 0–9% passing 0.063mm. Always confirm against the current project specification and supplier certificate.
Type 1 is a close-graded sub-base designed for strong compaction and interlock. Type 3 is more open graded and lower in fines, making it more suitable for permeable pavement and drainage applications. Type 1 is commonly used below driveways, patios and roads where a dense sub-base is required; Type 3 is preferred where water needs to pass through the layer.
No. “20mm aggregate” only describes a nominal size. Concrete aggregate also needs the correct grading, particle shape, cleanliness, strength, water absorption and durability. Thin slabs, reinforced sections and pumped concrete may need a smaller maximum size or a combined aggregate grading designed by the concrete supplier.
Yes, recycled aggregate can be suitable when it is processed, graded and certified to the required specification. However, recycled aggregate must be checked for composition and contaminants such as asphalt, glass, wood, plastic, gypsum and metals. For highways or engineered works, use the project clause and supplier certificate rather than visual judgement alone.
The designation 0/31.5 means the aggregate includes particles from fines up to a nominal upper sieve size of 31.5mm. It does not mean every particle is exactly below 31.5mm in all circumstances; specifications normally allow controlled oversize and define grading categories. The exact acceptance range is shown in the relevant grading table.
The 0.063mm sieve is used to measure fines. Fines strongly affect water demand, drainage, frost susceptibility, cohesion and compaction behaviour. A small quantity of fines can help a close-graded material compact, but too much can make aggregates water-sensitive and unsuitable for drainage or structural layers.
Related UK Construction Guides & Guides
More free resources to help specify aggregates, concrete, screed and sub-base materials.
For additional concrete quantity and estimating resources, you can also visit ConcreteCalcs.com.