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NHBC issues technical alert regarding the use of concrete facing bricks

House Building Standards Technical Alert - concrete facing bricks

What is this about?

As a result of the upturn in house building activity and the associated shortage of some building materials, NHBC are becoming increasingly aware of situations where 'substitute' materials, products and systems are being used on-site.

The use of concrete facing bricks rather than the originally intended clay bricks seems to be a recurring issue, no doubt due to the current difficulties in obtaining clay bricks. Concrete facing bricks have been used successfully for many years, but the implications of using them must be thoroughly considered as there are important issues relating to the performance characteristics of concrete.

What is the issue?

The most significant of these are moisture/thermal movement and creep. The correct positioning of movement joints is absolutely critical to the prevention of cracking in the outer leaf of brickwork and by association will help to ensure satisfactory long term in-service performance.

What do I need to do?

Guidance for the spacing of movement joints in walls constructed of concrete facing bricks can be found in NHBC Standards Chapter 6.1 'External masonry walls'. Clause 6.1 - D3(g) suggests that movement joints in walls constructed of concrete brick should be spaced at no more than 6m intervals.

There may be occasions where concrete facing bricks could be used with movement joints spaced further apart than 6m. This could be acceptable with the strict proviso that appropriate evidence is provided to NHBC to confirm that the implications of adopting a wider spacing have been fully taken into account. Taking note of the requirements set out in BS 5628-3 Clause 5.4.2.3.6 (Spacing and width of movement joints in concrete masonry), would be one recognised method of proving likely performance.

If in doubt contact the Standards & Technical Helpline on 01908 747387 for further information.

Media contacts at NHBC

James Hall  on 01908 746 738

News Date: 08/04/14