The Role of Engineering Bricks in Load-Bearing Structures

24th May 2024 -

Engineering bricks are vital in the construction of load-bearing structures. This article explores the unique properties of engineering bricks, their applications in load-bearing structures and the benefits they offer. 

What is an engineering brick?

Engineering bricks are manufactured for structural applications where high compressive strength is required. Unlike common clay bricks which are used for non-load-bearing structures, engineering bricks undergo rigorous production processes to meet stringent criteria.

They are made from a blend of raw materials such as fire clay, shale and additives that boost structural properties. These ingredients are formed into bricks and fired in a kiln at temperatures above 1,000°C (1,832°F). The intense heat creates vitrification, a process where the clay particles partially melt and fuse, removing porosity.

The result is a dense engineering brick with a compressive strength typically ranging from 20 to 50 megapascals (MPa). An MPa is a unit used to measure compressive strength, indicating how much pressure a brick can withstand before cracking. Brick colours vary from red to brown and blue depending on the composition of the raw materials.

Standard

A rectangular unit made in standard metric size dimensions like modular (200x100x65mm) and utility (240x115x73mm) formats. Generally, they are either brown or red engineering bricks. Used for all typical structural applications.

Perforated

Vertically hollow perforations with similar modular or utility dimensions as standard bricks but are lightweight. 

Bullnose

A brick with 1 rounded edge along the standard modular-sized unit. Used as trim to finish exposed external corners.

Imperial

Larger units measuring 215x102x64mm. You can lay these bricks for heavy industrial and commercial construction.

Buff

Similar to modular or utility engineering brick size but made from lighter buff/yellow mud. This creates a lighter colour vs typical red or brown hues. Buff engineering bricks are primarily used for aesthetic purposes.

Textured

Standard modular or utility dimensions with textured faces like scored lines for decorative masonry purposes.

Glazed

Typical metric sizes but with an exterior glaze coating in various colours. This includes blue engineering bricks for a glossy finish. 

Angle

Pre-formed with an angled edge in modular dimensions. 

Learn more about the properties of engineering bricks with our comprehensive guide.

Are engineering bricks waterproof?

They are not completely waterproof on their own. Proper waterproofing measures and detailing are required. This is especially for applications with high moisture exposure like basements and exterior walls. The degree of waterproofing provided by engineering bricks depends on their classification and water absorption properties.

The dense composition of engineering bricks limits water penetration. However, some absorption still occurs. Class A engineering bricks with maximum 24-hour cold water absorption rates under 4.5% provide the highest moisture resistance. When combined with waterproof membranes and proper drainage detailing, they form an effective barrier against moisture infiltration.

Class B engineering bricks contain absorption rates up to 7%. They can be made more moisture resistant through the use of water-repellent admixtures added during manufacturing. This enhances their ability to prevent moisture damage from factors like wind-driven rain. 

5 load-bearing structures using engineering bricks

Engineering bricks are extensively used in a wide range of load-bearing structures. The choice of brick class depends on the structural requirements and anticipated load conditions. Below, we detail the main applications for engineering bricks.

1. Foundations and basements

Moisture resistant bricks are crucial for below-grade foundation walls and basement construction. Engineering class A bricks with a minimum compressive strength of 27.6 MPa are commonly specified. Their low porosity provides resistance against groundwater and capillary action. 

2. Load-bearing walls

Engineering class B bricks with 20.7 MPa are suitable for load-bearing walls in low to medium-rise construction like residential housing. This class allows for reduced wall thickness while supporting the imposed loads. Proper bonding and steel reinforcement increase lateral stability.

3. Lintels and columns

For concentrated load transfer over openings and column construction, engineering bricks of Class A or B can be used. Their high strength prevents failure under point loads (a force used on a concentrated point on a support). They also allow for slender profiles. Steel reinforcement enhances the tensile capacity for lintels spanning large distances.

4. Industrial structures

Heavy industrial buildings require class A engineering bricks that meet a specific benchmark of 27.6 MPa. The added strength accommodates substantial loading from equipment, storage and multi-story construction. Lateral wind loads are a key consideration in tall chimneys made from engineering bricks.

5. Historical structures

Many heritage buildings used low water absorption, high firing engineering quality bricks that have demonstrated longevity. For restoration inspired by traditional styles, the class B engineering brick option offers 20.7 MPa strength and matches historical aesthetics. 

What are the UK building regulations for engineering bricks?

When constructing load-bearing structures using engineering bricks, you must ensure compliance with the relevant Building Regulations 2010 sections. They set out minimum standards for structural safety, materials and labour.

• Structural safety (Part A): Load-bearing walls must be constructed to safely transfer all applied loads to the ground through adequate foundations without causing damage. Guidance is provided on strengths, wall thicknesses, height/width ratios and lateral support requirements based on class. 
• Materials and workmanship (Part A): Engineering bricks must adhere to BS EN 771-1 for compressive strength, absorption, density and dimensional criteria for their class. Mortar should also meet standards for prescribed mix compositions.
• Moisture resistance (Part C): For resistance to groundwater and water penetration, Class A engineering bricks are required for exterior walls up to ground level. Acceptable levels of environmental exposure must be assessed.
• Drainage (Part H): Provisions must be included to allow moisture drainage and ventilation for cavity walls using engineering bricks. These provisions include weep holes and cavity trays. 
• Stability (Part A): Brickwork must be properly bonded, secured at joints/intersections and supported by lintels to prevent instability and collapse. Movement joints are required at set intervals.
• Protection from falling (Part K): For brick masonry over 2m high or near edges, suitable brick guards, scaffolding or battens must be used during construction.

How to tackle issues with laying engineered bricks

Addressing issues like weather exposure and concentrated loads is also critical to preventing cracking and ensuring the long-term durability of the masonry assembly. Here, we outline how to combat these issues for a smooth construction process. 

Dimensional tolerances

The dimensions of engineering brick have tight tolerance requirements. These typically range from below or over 3mm. This maintains consistent joint thicknesses and ensures proper structural performance. 

Solution: Carefully inspect each brick delivered and remove any units not meeting tolerance. During construction, precise layout lines, gauging rods and frequent checking with a mason's level are required. 

Restricted mortar joints

Specifications limit mortar joint thicknesses to 6-10mm for engineered brick to reduce pathways for moisture penetration and increase strength.

Solution: Use a firm consistency mortar that is easily worked into thin joints without voids or bridging. Proper tooling techniques like raking or concaving compact mortar ensure full joint thickness. Using a club-headed jointing tool helps with compaction.

Slow curing

Low absorption rates of engineer brick prevent the rapid transfer of curing moisture from the fresh mortar into the units. This prolongs cure times compared to standard masonry.

Solution: Allow for a longer curing period by covering fresh masonry with plastic tarps or pre-sized curing blankets to reduce evaporation. Adjusting schedules and sequencing to allocate more time between lifts is also required.

Weather exposure

During construction, the low absorption rates make fresh engineering brick masonry more susceptible to moisture issues. These include staining and efflorescence from driving rains or freezing conditions.

Solution: Properly cover the tops of walls and protect completed sections by wrapping them with tarpaulins secured against wind. Heated enclosures may be required for winter construction below freezing to allow mortar to gain strength before exposure.

Low moisture movement

Engineering bricks exhibit very minimal expansion when wetted compared to clay masonry units, requiring proper accommodation for differential movement.

Solution: Introduce adequate control and expansion joints based on project specifications and wall lengths/heights to prevent cracking. Using a flexed masonry bond beam detail allows expansion while transferring vertical loads.

Concentrated loads

The high compressive strength of engineering bricks still allows internal micro-cracking under excessive localised construction loads.

Solution: Distribute any stacked material loads evenly over solid, braced areas of masonry. Avoid walking on unprotected areas of fresh masonry before it gains strength. Install required bracing and shore walls per code during construction.

Can you drill into engineering bricks?

While the composition provides excellent compressive strength, it also presents challenges when drilling is required for anchors, ties or embedments. 

Drilling limitations

Because of their hardness, drilling into an engineering brick can be complicated compared to a standard clay brick. The risk of spalling, cracking or shattering the brick increases significantly, especially with larger diameter holes. This could potentially compromise structural integrity. 

When drilling is necessary, it should be limited to smaller diameter holes (under 10mm). You should use masonry drill bits designed for low-porosity materials. Proper drill speed and applied pressure are critical to prevent damage to the brick.

Alternative anchoring methods

To avoid compromising the engineering bricks, alternative anchoring methods that do not require drilling are preferable.

• Use masonry ties built into the bed joints during construction.
• Secure embeds or anchors into the mortar joints rather than the brick itself.
• Bolt anchors into pre-formed holes in special slotted engineering bricks.
• Epoxy adhesive anchoring systems into pre-drilled holes in the mortar joints.

Any holes drilled into load-bearing engineering brick masonry should be properly filled and sealed with mortar to maintain integrity.

How much maintenance do engineering bricks require?

A major benefit of engineering bricks is their low maintenance requirements. Their durable composition provides superior resistance to weathering, moisture and deterioration.

Inspection frequency

For most applications, a yearly visual inspection of the engineering brickwork from ground level is sufficient. This allows for the identification of any cracks, spalling or efflorescence build-up that may require remedial work.

Frequent inspections, such as quarterly or twice a year, could be warranted for exposures like coastal environments or industrial pollution.

Cleaning techniques

If cleaning is required because of built-up dirt, efflorescence or staining, be sure to use gentle cleaning methods.

• Low-pressure water rinsing.
• Mild detergent solutions and soft brushes for scrubbing.
• Commercial concrete and masonry-approved cleaners.

Avoid using high-pressure washers, acid-based cleaners or harsh abrasives. They may cause damage or erode the brick surfaces over time.

Repointing mortar joints

Over decades of exposure, deterioration of the mortar joints between bricks is normal. Repointing by raking out old mortar and reapplying new mortar helps restore the structural integrity of the masonry.