BS 8500 Guide (Parts 1 & 2) | ConcreteMaths.com

The definitive free UK guide to BS 8500 — the concrete specification standard. Covers all designated mix families, exposure classes, consistence classes, ordering procedures, and the relationship with BS EN 206. Updated for 2026.

What Is BS 8500? — UK Concrete Specification Standard

BS 8500is the British Standard that defines how concrete is specified and ordered in the UK. It comprises two parts:BS 8500-1(Method of specifying and guidance for the specifier) andBS 8500-2(Specification for constituent materials and concrete). Together they provide the complete framework for selecting, ordering, delivering, and verifying concrete for all UK construction applications.

BS 8500 and BS EN 206 — The Relationship

BS 8500 is the UK complementary standard to the European standardBS EN 206. BS EN 206 sets the European framework for concrete specification; BS 8500 provides the specifically UK-adapted guidance including the UK’s own designated concrete mix system (GEN, RC, FND, PAV, DC) which does not exist in BS EN 206 alone. All concrete ordered to BS 8500 automatically complies with BS EN 206.

BS 8500-1: Specifying

Guidance for engineers, architects, and contractors on how to select the correct mix type, exposure class, strength class, and additional requirements. Includes all designated concrete tables used for ordering.

BS 8500-2: Production

Specifies the requirements for concrete producers — constituent materials, mix proportions, production control, conformity testing, and delivery documentation. Governs how your ready-mix plant produces the concrete you order.

Delivery Ticket

Every load of concrete supplied under BS 8500 must be accompanied by a delivery ticket (BS EN 206 Clause 11.8) confirming the designation, strength class, consistence, aggregate size, cement type, and batch details.

Who Must Use BS 8500?

BS 8500 applies to virtually all concrete used on UK construction projects. It is referenced by:

Approved Document A(Building Regulations — Structure) for foundation concrete specifications
The Concrete Centredesign guides for structural concrete
Building Control inspectors when verifying foundation and slab specifications
Structural engineers preparing foundation and slab specifications
Ready-mix plants, volumetric operators, and bagged concrete manufacturers when declaring product conformity

For domestic DIY projects, BS 8500 designated mixes provide a simple and reliable way to order the correct concrete without needing a structural engineer to prepare a designed mix specification.

BS 8500 Designated Concrete Mix Families

BS 8500-1 defines five families ofdesignated concretepre-defined mix types identified by a letter code and number. They are the simplest way to order concrete for standard UK applications because the specifier only needs to state the designation and the concrete producer supplies a pre-defined, tested mix.

General Purpose Concrete

For non-structural applications where strength and exposure requirements are modest. GEN 0 to GEN 4 cover a range of basic construction uses. The simplest and most economical designated concrete family.

Reinforced Concrete

For structural applications requiring higher strength and durability. RC 25/30 through RC 50/60 cover the full range from domestic foundations to commercial structural elements. The most widely used designated family.

Foundation Concrete

Specifically designed for foundations in sulphate-bearing ground. FND 2 through FND 4Z provide increasing resistance to sulphate attack — critical on sites with sulphate-containing soils such as made ground, colliery spoil, or gypsum-bearing strata.

Pavement Concrete

Optimised for external paving, driveways, and surfaces exposed to freeze-thaw cycling and de-icing salts. PAV 1 for ordinary external paving; PAV 2 for surfaces exposed to de-icing salts — both require air entrainment for frost resistance.

Designated Concrete for Aggressive Ground

DC (Designated Concrete) mixes are for chemically aggressive ground conditions. DC-1 to DC-4 provide graded levels of chemical resistance — always requires a ground investigation report and chemist’s assessment before specification. Superseded FND for most aggressive ground.

Standardised Prescribed & Strength Classes

ST mixes (ST1–ST5) are standardised prescribed mixes used on smaller jobs where exact proportions are specified. C-class strength designations (C16/20, C25/30 etc.) are used for designed concrete where the engineer specifies performance requirements directly rather than using a designated mix.

Quick Reference — Which Mix Family for Common UK Projects?

BS 8500 Designated Mix Reference Table 2026

The table below shows the key technical requirements for each BS 8500 designated concrete family, based on BS 8500-1:2015+A2:2019 Table A.3 and Table A.5. All values assume 20mm maximum aggregate size unless noted.

Designation: GEN 0; Strength Class: C8/10; Min Cement (kg/m³): 180; Max w/c: —; Exposure Class: X0; Typical Application: Blinding, mass fill; Notes: No freeze-thaw exposure
Designation: GEN 1; Strength Class: C12/15; Min Cement (kg/m³): 200; Max w/c: —; Exposure Class: X0/XC1; Typical Application: Kerb bedding, haunching; Notes: —
Designation: GEN 2; Strength Class: C16/20; Min Cement (kg/m³): 220; Max w/c: —; Exposure Class: XC1; Typical Application: Steps, paths (sheltered); Notes: —
Designation: GEN 3; Strength Class: C16/20; Min Cement (kg/m³): 240; Max w/c: 0.70; Exposure Class: XC1; Typical Application: Garage base, shed base; Notes: —
Designation: GEN 4; Strength Class: C20/25; Min Cement (kg/m³): 240; Max w/c: 0.70; Exposure Class: XC1; Typical Application: Drain haunching; Notes: —
Designation: RC 25; Strength Class: C25/30; Min Cement (kg/m³): 260; Max w/c: 0.65; Exposure Class: XC2; Typical Application: Strip foundations; Notes: Most Common
Designation: RC 28; Strength Class: C28/35; Min Cement (kg/m³): 270; Max w/c: 0.60; Exposure Class: XC2; Typical Application: Ground slabs, driveways; Notes: —
Designation: RC 32; Strength Class: C32/40; Min Cement (kg/m³): 280; Max w/c: 0.60; Exposure Class: XC3/XC4; Typical Application: Reinforced floor slabs; Notes: —
Designation: RC 40; Strength Class: C40/50; Min Cement (kg/m³): 300; Max w/c: 0.55; Exposure Class: XC4; Typical Application: Beams, suspended slabs; Notes: Engineer req.
Designation: RC 50; Strength Class: C50/60; Min Cement (kg/m³): 320; Max w/c: 0.45; Exposure Class: XC4; Typical Application: Columns, frames; Notes: Engineer req.
Designation: PAV 1; Strength Class: C28/35; Min Cement (kg/m³): 300; Max w/c: 0.60; Exposure Class: XF3; Typical Application: External paving; Notes: Air entrained
Designation: PAV 2; Strength Class: C32/40; Min Cement (kg/m³): 320; Max w/c: 0.55; Exposure Class: XF4; Typical Application: De-icing salt exposure; Notes: Air entrained
Designation: FND 2; Strength Class: C25/30; Min Cement (kg/m³): 280; Max w/c: 0.65; Exposure Class: AC-2; Typical Application: Sulphate ground foundations; Notes: SRPC or GGBS blend
Designation: FND 3; Strength Class: C25/30; Min Cement (kg/m³): 320; Max w/c: 0.60; Exposure Class: AC-3; Typical Application: Moderate sulphate; Notes: SR cement required
Designation: FND 4; Strength Class: C35/45; Min Cement (kg/m³): 360; Max w/c: 0.50; Exposure Class: AC-4; Typical Application: High sulphate; Notes: SRPC + engineer

Values Are Guide Figures — Always Confirm with Your Supplier

The values in this table are based on BS 8500-1:2015+A2:2019. Specific mix proportions vary between concrete producers. Your supplier’s delivery ticket is the definitive record of the mix supplied. For structural applications, always obtain written confirmation from your supplier that the mix meets the designated concrete requirements of BS 8500-2. See theordering guide belowfor the information you need to provide when placing an order.

BS 8500 / BS EN 206 Exposure Classes — Complete 2026 Guide

Exposure classes define the chemical and physical conditions to which concrete will be exposed during its service life. They directly determine the minimum concrete grade, cement content, and water-cement ratio specified in BS 8500. Every concrete specification must identify the relevant exposure class(es).

UK Note — Multiple Exposure Classes

Most real UK concrete elements are subject to more than one exposure class simultaneously. For example, an external foundation in mildly sulphate-bearing ground would be classified XC2 (carbonation) + XA1 (chemical attack). The specification must satisfy all applicable classes — the most demanding requirements of any applicable class govern the minimum cement content, maximum w/c ratio, and minimum strength class.

BS EN 206 Consistence Classes — Slump & Flow 2026

Consistence (workability) defines how easily fresh concrete flows and is placed. BS EN 206 defines consistence using slump classes (S1–S5) for most applications, and flow classes (F1–F6) for self-compacting concrete. You must specify the consistence class when ordering — it affects pumpability, compaction, and finish quality.

Class: S1; Slump Range: 10–40mm; Description: Very stiff; Typical UK Applications: Road bases, trench fill (self-compacting ground); Pump Suitable?: Not Suitable
Class: S2; Slump Range: 50–90mm; Description: Stiff; Typical UK Applications: Strip foundations, unreinforced slabs; Pump Suitable?: Marginal
Class: S3; Slump Range: 100–150mm; Description: Medium; Typical UK Applications: Reinforced slabs, general pours — most common domestic; Pump Suitable?: Yes
Class: S4; Slump Range: 160–210mm; Description: Soft / Flowing; Typical UK Applications: Pumped concrete, complex reinforced elements; Pump Suitable?: Preferred
Class: S5; Slump Range: ≥ 220mm; Description: Very fluid; Typical UK Applications: Self-compacting / self-levelling, inaccessible areas; Pump Suitable?: Yes

Never Add Water to Increase Slump On-Site

Adding water to ready-mix concrete after batching is one of the most damaging things you can do. Every litre of additional water per m³ reduces compressive strength by approximately 5% and increases shrinkage cracking risk. If the delivered concrete is too stiff, contact your supplier — they can add a plasticiser (superplasticiser admixture) at the plant before dispatch. Adding water on-site invalidates the BS 8500 mix specification and the supplier’s quality guarantee.

How to Order Concrete to BS 8500 — UK Guide 2026

Ordering concrete to BS 8500 correctly ensures you receive the right product, with documented evidence of compliance. The following information must be communicated to your supplier when placing an order for designated or designed concrete.

Minimum Information Required When Ordering (BS 8500-1 Clause 5)

Concrete type:Designated (e.g. RC 25), designed, prescribed, or standardised prescribed
Designation or strength class:e.g. RC 25, C25/30, PAV 1
Consistence class:S2, S3, S4 (or target slump in mm if agreed with supplier)
Maximum aggregate size (D_max):Typically 10mm, 14mm, 20mm, or 40mm
Chloride class:Cl 0.10 for reinforced concrete; Cl 0.40 for plain concrete
Volume required (m³):Net volume + waste allowance, rounded to 0.25m³
Delivery date and time:For ready-mix — typically 24–72 hours notice required
Delivery address and access details:Postcode, site contact, lorry access constraints

The BS EN 206 Delivery Ticket — What to Check

Every load of ready-mix concrete must be accompanied by a delivery ticket. When the lorry arrives, check the ticket confirms:

Supplier name and plant addressconfirms the concrete comes from a BS EN 206-compliant production facility
Designation or strength classmust match your order exactly (e.g. RC 25 / C25/30)
Consistence classS2, S3 etc. or target slump
Cement type and content (kg/m³)must meet BS 8500-2 minimum for the designation
Water-cement ratiomust not exceed the BS 8500 maximum for the designation
Maximum aggregate sizemust match order
Chloride classCl 0.10 or Cl 0.40
Volume of load (m³)verify against your order
Batch timeconcrete must be placed within 90 minutes of batching (or 300 drum revolutions)
Lorry number and delivery note numberfor traceability

Reject Any Load Without a Delivery Ticket

A delivery ticket is not optional — it is a mandatory requirement under BS EN 206 Clause 11.8. Without it, you have no documented evidence that the concrete supplied meets your specification. This matters for Building Control submissions, structural insurance, and future property sale. If a lorry arrives without a delivery ticket, reject the load and contact your supplier immediately. Reputable UK suppliers never deliver without a ticket.

BS 8500 vs BS EN 206 — What’s the Difference?

These two standards are complementary, not competing. Understanding how they relate helps you order correctly and understand supplier documentation.

BS 8500 — UK National Annex

The British Standard that implements BS EN 206 for UK-specific conditions. Contains the UK’s designated concrete system (GEN, RC, PAV, FND, DC), UK exposure classes for sulphate ground, and guidance specific to UK practice. Used by UK engineers and contractors when specifying and ordering concrete.

BS EN 206 — European Standard

The harmonised European standard for concrete specification, production, and conformity. Sets the framework for exposure classes (XC, XD, XS, XF, XA), strength classes (C8/10–C100/115), consistence classes, and delivery ticket requirements. Applies across all EU and EEA countries plus the UK.

In Practice

When you order RC 25 to BS 8500, your supplier produces concrete that meets both BS 8500-2 and BS EN 206 simultaneously. The delivery ticket references both standards. For Building Control submissions, reference BS 8500 — it is the standard directly cited in Approved Document A.

Aspect: Scope; BS 8500 (UK): UK national complement to EN 206; BS EN 206 (European): Pan-European harmonised standard
Aspect: Designated mixes; BS 8500 (UK): Yes — GEN, RC, PAV, FND, DC; BS EN 206 (European): No — designed and prescribed only
Aspect: UK sulphate classes; BS 8500 (UK): AC-1 to AC-5 classification; BS EN 206 (European): XA1–XA3 only
Aspect: Building Regulations; BS 8500 (UK): Directly referenced in Appr. Doc A; BS EN 206 (European): Indirectly via BS 8500
Aspect: Delivery ticket; BS 8500 (UK): As per EN 206 Clause 11.8; BS EN 206 (European): Mandatory — Clause 11.8
Aspect: Conformity testing; BS 8500 (UK): BS 8500-2 production control; BS EN 206 (European): EN 206 conformity criteria
Aspect: Post-Brexit status; BS 8500 (UK): UK retained standard (BSI); BS EN 206 (European): Retained as UK-adopted EN standard

BS EN 206 Concrete Strength Classes — Complete Reference

Concrete strength is expressed as a strength class in the formatCf_ck,cyl/f_ck,cubethe characteristic compressive strength of a cylinder at 28 days / characteristic compressive strength of a cube at 28 days, both in N/mm². The cylinder strength is always lower (by approximately 20%) because cylinders fail at lower loads than cubes of the same mix.

Strength Class: C8/10; Cylinder (N/mm²): 8; Cube (N/mm²): 10; Old Notation: —; Typical Designation: GEN 0; Common Application: Blinding, mass concrete fill
Strength Class: C12/15; Cylinder (N/mm²): 12; Cube (N/mm²): 15; Old Notation: —; Typical Designation: GEN 1; Common Application: Kerb bedding, haunching
Strength Class: C16/20; Cylinder (N/mm²): 16; Cube (N/mm²): 20; Old Notation: C20P; Typical Designation: GEN 3/4; Common Application: Garage base, domestic slab
Strength Class: C20/25; Cylinder (N/mm²): 20; Cube (N/mm²): 25; Old Notation: C25P; Typical Designation: GEN 4; Common Application: Non-structural general use
Strength Class: C25/30; Cylinder (N/mm²): 25; Cube (N/mm²): 30; Old Notation: C30P; Typical Designation: RC 25; Common Application: Strip foundations — most common domestic
Strength Class: C28/35; Cylinder (N/mm²): 28; Cube (N/mm²): 35; Old Notation: C35P; Typical Designation: RC 28 / PAV 1; Common Application: Ground slabs, driveways, paving
Strength Class: C32/40; Cylinder (N/mm²): 32; Cube (N/mm²): 40; Old Notation: C40P; Typical Designation: RC 32 / PAV 2; Common Application: Reinforced slabs, retaining walls
Strength Class: C35/45; Cylinder (N/mm²): 35; Cube (N/mm²): 45; Old Notation: —; Typical Designation: FND 4 / RC 35; Common Application: High-sulphate foundations
Strength Class: C40/50; Cylinder (N/mm²): 40; Cube (N/mm²): 50; Old Notation: —; Typical Designation: RC 40; Common Application: Structural beams, suspended slabs
Strength Class: C50/60; Cylinder (N/mm²): 50; Cube (N/mm²): 60; Old Notation: —; Typical Designation: RC 50; Common Application: Columns, structural frames
Strength Class: C60/75; Cylinder (N/mm²): 60; Cube (N/mm²): 75; Old Notation: —; Typical Designation: Designed only; Common Application: High-rise columns, specialist
Strength Class: C100/115; Cylinder (N/mm²): 100; Cube (N/mm²): 115; Old Notation: —; Typical Designation: Designed only; Common Application: Reactive powder / ultra-high strength

Old C-Notation vs New Dual Notation

Before BS EN 206 was adopted in the UK, concrete grades were expressed as a single cube strength: C20, C25, C30 etc. These are now officially expressed as dual-notation strength classes: C20 = C16/20, C25 = C20/25, C30 = C25/30, C35 = C28/35, C40 = C32/40. However, many UK suppliers and contractors still use the old single-number notation informally — always confirm which system your supplier is using when comparing quotes to ensure you are ordering the same product.

Always Confirm Your Specification with Your Supplier Before Ordering

This BS 8500 guide is a free reference resource for UK construction projects. Mix selector figures are indicative only — always confirm the final specification with a qualified structural engineer for structural applications, and with your concrete supplier to verify that the designated mix meets all applicable exposure classes for your specific site. Use ourmix selector toolas a starting point, not a definitive specification.

BS 8500 — Frequently Asked Questions 2026

Answers to the most common questions about ordering and specifying concrete to BS 8500 in the UK.

GEN (General Purpose):For non-structural applications — paths, garage bases, steps, blinding. GEN 0–GEN 4. No minimum strength specified for most GEN mixes — they are defined by cement content and w/c ratio, not performance requirements. Cheapest family.
RC (Reinforced Concrete):For structural and semi-structural applications — foundations, floor slabs, retaining walls. RC 25 through RC 50/60. Defined by strength class (C25/30 upwards) and exposure class. The most widely used family for domestic construction.
PAV (Pavement):For external paving, driveways, and surfaces exposed to freeze-thaw cycling and de-icing salts. PAV 1 and PAV 2 — both are air-entrained to resist frost damage. Use PAV 1 for ordinary drives; PAV 2 where de-icing salts are used.

C25 (old notation) = C20/25 (new BS EN 206 strength class)characteristic cube strength of 25 N/mm²
RC 25 (BS 8500 designated)minimum characteristic strength of C25/30 (cube strength 30 N/mm²), PLUS minimum cement content of 260 kg/m³, PLUS maximum w/c of 0.65

Car driveway, no de-icing salts used:PAV 1 — C28/35, air-entrained, S3 consistence, 20mm aggregate
Car driveway where de-icing grit / salt is applied:PAV 2 — C32/40, air-entrained, S3, 20mm aggregate
Light van / small commercial traffic:PAV 2 minimum — consider RC 32 for heavily trafficked areas
HGV / heavy goods vehicles:Designed mix required — minimum C32/40 with structural engineer’s specification

FND 2:Use in Aggressive Chemical Class AC-2 ground — mild sulphate exposure. Contains sulphate-resisting Portland cement (SRPC) or Portland cement blended with GGBS or PFA.
FND 3:AC-3 ground — moderate sulphate. Higher cement content and lower w/c than FND 2.
FND 4:AC-4 ground — high sulphate. C35/45 minimum strength, 360 kg/m³ cement, SRPC mandatory.
FND 4M / FND 4Z:Specialist variants for high-magnesium or high-thiosulphate ground — rare and require specialist chemical engineer.

QSRMC (Quality Scheme for Ready Mixed Concrete):The main UK scheme — search for certified plants atqsrmc.co.uk
BSI Kitemark for BS EN 206 / BS 8500-2:Look for the BSI Kitemark on delivery tickets and supplier documentation
BRMCA membership:British Ready Mixed Concrete Association members commit to BS 8500 compliance — check atbrmca.org.uk
Delivery ticket format:A correctly formatted BS EN 206 delivery ticket is strong evidence of a compliant production system

Minimum strength class:C25/30 (RC 25 designated mix)
Minimum cement content:260 kg/m³
Maximum w/c ratio:0.65
Exposure class:XC2 minimum (wet, rarely dry — in contact with ground)
Sulphate ground:FND 2–4 as appropriate — upgrading to sulphate-resisting cement is mandatory in AC-2+ ground

BS 8500-1:2015+A2:2019:Current edition of Part 1 (specifier guidance). Amendment A2 (2019) updated the sulphate classification system and clarified DC-class concrete requirements to align with BRE Special Digest SD1 2005 (3rd edition).
BS 8500-2:2015+A2:2019:Current edition of Part 2 (production). Amendment A2 aligned constituent material and conformity requirements with the 2013 revision of BS EN 206.
BS EN 206:2013+A2:2021:The European parent standard was revised in 2021 (Amendment 2) — changes to recycled aggregate use, low-carbon cements, and structural lightweight concrete. BS 8500 will require further amendment to fully align.
Low-carbon cement guidance (2023 onwards):BSI and The Concrete Centre have issued updated guidance on the use of supplementary cementitious materials (GGBS, PFA, limestone fines) in line with net-zero commitments — relevant to BS 8500 cement type selection for all projects.