British Standards for Bricks: The Complete Guide

What Are British Standards for Bricks?

British Standards are technical specifications issued by the British Standards Institution (BSI). For bricks, these standards establish:

• Minimum performance levels
• Classification systems
• Test methods
• Durability and exposure ratings
• Dimensional accuracy
• Manufacturing requirements

While EU standards still influence some classifications, the UK continues to apply updated BS EN versions.

British Standards for Clay Bricks

These are the key British Standards that define how bricks are tested, classified and approved for use in UK construction. Understanding them helps ensure bricks are suitable for their intended application.

2. BS EN 771-1: Clay Masonry Units (Main Standard)

BS EN 771-1 is the primary British Standard covering clay bricks. It sets out the performance and quality requirements used to assess suitability for construction.

• Dimensional tolerances (T1, T2 and Tm)

• Compressive strength ratings

• Freeze–thaw resistance

• Water absorption limits

• Thermal performance

• Active soluble salt content

• Declared density

• Brick configuration, including solid, perforated and frogged bricks

Dimensional Tolerances (Accuracy & Finish)

Dimensional tolerances define how much variation is allowed in brick size, which affects accuracy, joint consistency and overall finish.

• T1 - Basic tolerance
  Suitable for general masonry work
• T2 - Precise tolerance
  Used where higher accuracy and tighter tolerances are required
• Tm - Manufacturer declared tolerance
  Brick dimensions must meet the manufacturer’s stated values

Compressive Strength (Structural Performance)

Compressive strength measures how much load a brick can safely carry and is expressed in megapascals (MPa).

Common strength classes:

• ≥ 5 MPa
• ≥ 7 MPa
• ≥ 12 MPa
• ≥ 20 MPa
• ≥ 40 MPa

For most structural and load-bearing masonry, bricks in the 20-40 MPa range are typically used.

Frost Resistance Classification

This classification shows how suitable bricks are for different environments based on their resistance to frost.

• F0 - Not frost resistant, suitable for internal use only
• F2 - Moderate frost resistance, suitable for sheltered external walls
• F3 - High frost resistance, suitable for all external applications

Water Absorption Classes

This classification groups bricks by their water absorption levels, which directly affect frost resistance and where the bricks can be safely used.

• Low water absorption (<7%) - Not frost resistant, suitable for internal use only
• Medium water absorption (7-12%) - Moderate frost resistance, suitable for sheltered external walls
• High water absorption (>12%) - High frost resistance, suitable for all external applications

Dimensional Requirements and Tolerances

This classification explains the standard brick sizes used in the UK, helping ensure compatibility with existing brickwork and consistent course heights.

• UK Standard size - 215mm x 102.5mm x 65mm
• Metric Standard size - 190mm x 90mm x 90mm
• Modular Sizes - Varies by manufacturer

Also worth noting:

• Imperial bricks - typically around 228mm × 108mm × 68mm
  Commonly found on pre-1965 buildings and important to consider when carrying out repairs, extensions or brick matching on older properties.

BS EN 998-2: Masonry Mortar Requirements

Brick performance depends heavily on compatible mortar. Exposure resistance, strength, and structural bonding are all influenced by mortar choice.

Common mortar types under BS EN 998-2:

• M2 (Low Strength Mortar)
  Used with soft or historic bricks, allowing movement and moisture transfer without damaging the masonry.
• M4 (General Purpose Mortar)
  Suitable for most standard residential brickwork, providing a balanced mix of strength, durability, and workability.
• M6 (Higher Strength Mortar)
  Used for structural or exposed masonry, offering greater load-bearing capacity and improved weather resistance.
• M12 (High Strength Mortar)
  Designed for engineering bricks and heavy structural applications where very high compressive strength is required.

BS EN 1996 (Eurocode 6): Design of Masonry Structures

Eurocode 6 governs structural design of brickwork, covering:

• Allowable unit strengths
• Design compressive strength
• Partial safety factors
• Lateral Load Resistance
• Load‑bearing wall requirements
• It ensures brick structures are designed safely when using BS EN 771‑tested units.

BS 5628 (Withdrawn but Still Referenced)

Although replaced by Eurocode 6, BS 5628 is still referenced in heritage and refurbishment projects:

• BS 5628-1 - Unreinforced masonry
• BS 5628‑2 - Reinforced masonry
• BS 5628‑3 - Materials

BS EN 13501-1: Fire Resistance Requirements

BS EN 13501‑1 classifies brickwork as Euroclass A1 (non‑combustible).

Fire resistance ratings (30-120 minutes) depend on:

• Wall thickness
• Mortar type
• Load‑bearing role
• Cavity structure

Fire performance is calculated using Eurocode 6 (BS EN 1996‑1‑2).

BS EN 771‑1: Salt Content and Efflorescence Control

BS EN 771‑1 Salt Classifications:

• S0 - No requirement
• S1 - Limited soluble salts (most UK bricks)

Low‑salt bricks reduce efflorescence and are essential for:

• Parapets
• Retaining walls
• Saturated brickwork
• Porous facings

Engineering Bricks and Their Standards

This classification defines the performance of engineering bricks based on compressive strength and water absorption, making them suitable for structural and damp-resistant applications.

Class A engineering bricks

• Compressive strength: ≥ 125 MPa
• Water absorption: ≤ 4.5%

Class B engineering bricks

• Compressive strength: ≥ 75 MPa
• Water absorption: ≤ 7%

Engineering bricks are commonly used for foundations, damp-proof courses, manholes, retaining walls and other high-load or moisture-exposed areas.

Quality Assurance and On‑Site Compliance

To meet UK building regulations, bricks must be CE or UKCA marked, confirming they comply with the relevant British Standards and declared performance values.

The marking should clearly show:

• Declared compressive strength

• Density

• Freeze–thaw rating

• Tolerance class

• Durability rating

• Water absorption level

• Manufacturer identification

Always check pallet labels and documentation on delivery to ensure the bricks supplied match the project specification and site requirements.

Need Further Help?

Selecting the correct brick specification is essential for ensuring performance, compliance, and a high-quality finish. With so many options available across British Standard classifications, finding the most suitable brick for your project can sometimes be challenging.

Our experienced Trade Account Managers are here to help. Whether you're working on a new build, home extensions, refurbishment or a large commercial development, we can guide you through the available options and help you source the most appropriate brick for the job.

Through our strong relationships with leading manufacturers and our extensive industry knowledge, we can help you quickly identify bricks that meet the relevant British Standards and project specifications.

Speak to our team today to discuss your project requirements.