How Brick Durability Ratings are Determined & Why It Matters

30 May, 2022

brick durability ratings

Find out how a brick’s durability rating is determined. This will help you know more about the quality of bricks you need for your project’s exact design and specification.

What is Brick Durability?

The durability of bricks refers to the maximum time they remain unaltered and strong when used in construction.

Furthermore, experience has shown that properly manufactured bricks rank among the most durable man-made construction materials. As a result, surviving Roman architecture stands as evidence, lasting centuries and exemplifying the long lifecycle of these bricks.

Brick durability is affected by several factors. These include the physical properties of the bricks and mortars. The degree of exposure to the building also matters. Factors such as absorption value and frost resistance play a part in long-term brick durability. The less water a brick absorbs, the more frost resistant it is.

Where the bricks will be used, and when they are laid, also impacts the lifecycle. Brickwork is particularly at risk during winter construction. Incomplete and new brickwork must be adequately protected from both saturation and frost.

Why does Brick Durability Matter?

Clay bricks typically weather and age aesthetically. Brick constructions, when designed and built well, using appropriate materials, stand the test of time.

In extreme conditions, such as constant dampness or regular freezing, engineering bricks come into play. These bricks are frequently utilised in the construction of manholes and sewers. Featuring a smooth finish and several core holes for adding mortar or steel bar reinforcement, engineering bricks possess high compressive strength, making them ideal for damp coursing and tunnel construction.

Brickwork becomes vulnerable in locations with prolonged saturation, such as at or near ground level below damp course proofing (DCP), foundations, free-standing and retaining walls, parapets, chimney stacks, cappings, copings, sills, and chimney terminals.

External works, particularly between ground level and DPC, face more severe exposure compared to the rest of the building.

Enemies of Brick Durability

Environmental conditions, such as harsh weather conditions can cause bricks to erode. Direct damage can literally smash bricks to dust. Water saturation levels differ, dependent on brick composition. But too much water can cause dilution and subsequent weakening of the binding mortar. Too little water can lead to the brick absorbing water from the mortar, leading to cracks.  Water inside brick pores freezes, and so expands. This can lead to stress cracks forming, affecting the integrity of the brick.

There is a link between high exposure areas and the likelihood of brickwork suffering the consequences of frost attack if it has not been designed and constructed properly.  Areas within 8km of the coast and major river estuaries, and buildings on high ground are particularly vulnerable.

Sulphate attack is a rarer occurrence, resulting from a chemical reaction between soluble salts and a constituent of the cement in the mortar. This reaction leads to cracking on the surface of the mortar joint, crumbling and expansion on the inside, and disruption of the brickwork.

BS EN 771-14 distinguishes three categories of soluble salt content:

  • Category S0: bricks are not subject to any limits on specified soluble radicals and are intended for use in situations where total protection against water penetration is provided
  • Category S1: bricks have limits on soluble salt contents e.g. sodium, potassium and magnesium
  • Category S2: bricks have lower limits than Category S1 bricks.

Experience shows that the use of Category 2 clay bricks reduces the risk of sulfate attack on the mortar.

How are Brick Durability Ratings Determined?

Bricks fall into three durability categories:

  • F2 – Frost resistant: suitable for use in normal building situations and exposure levels
  • F1 – Moderately frost resistant: durable except where they remain saturated, and subject to freezing and thawing. Generally suitable for brickwork between DCP and eaves, F1 bricks should never be used below DCP, for plinths and projecting details, nor in landscaping. Use with caution, depending on level of exposure
  • F0 – Not frost resistant: not suitable for external use

Bricks without a durability rating are assumed to be F0 and should be used accordingly. Some F2 products may have a durability warranty if the correct design details are applied.

Although bricks may differ in appearance, they may look similar. Always check the brick’s rating against the one you need. Alternatively, reach out to our brick specialists for expert guidance in finding the ideal brick for your building.

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