It can be hard to keep up with all the standards for building products, especially as they frequently change. In this column, Barry Hunt throws some light on the standards, identifying those you need and those you don’t. This time he looks at BS 1341, external paving.

Way back in 2000, paving was seen as being possibly the most important use of stone in the public realm, so the early publication of a product standard was necessary.

This standard was produced and published and became one of the first for natural stone materials. It was updated in 2001 but has remained unchanged for a more than a decade, which seems unusual for a standard these days. It is due an update, so if you are thinking of buying this standard it might be worth waiting just a little longer if your needs are not too pressing.

Presently priced at £156, you get 44 pages, of which seven are titles and other sundry standard pages. The remaining pages are packed with useful information relating to dimensional tolerances for different classes of material and the testing requirements.

This is a rare standard in that it includes an actual pass/fail criterion for stone subjected to frost resistance testing if there is a likelihood of frost in the location of use – which is pretty much everywhere in the UK. If a paving stone is not classed as F1, I just would not use it.

A bonus of this standard is that it includes within its Annexes the tests for abrasion resistance and slip resistance, so there is no need to go and buy these standards separately, it seems. However, there are anomalies between the tests as written here and the current versions of the separate abrasion and slip standards.

BS 1341 notes that a pendulum value greater than 35 is generally considered safe, which still is in line with the current guidance from the HSE. The standard runs through the need for type testing and then factory production control. However, it neglects to determine how often such testing should be undertaken, something that should be addressed in the next version of the standard.

One of the most useful parts of the standard is Annex B, which shows how to calculate the breaking load of slabs.

There is a handy table that provides different categories of use and the related minimum required breaking load for each category.

Often it is easiest to start a road pavement design by determining the minimum thickness at which a given paver can be used. Everything else then tends to fall into place. The calculation is especially handy when looking at long and slender stone elements, where the thickness may need to be increased considerably to cope with the significantly increased potential for breakage.

This standard was an excellent start to the European norm experience for natural stone and it si a shame the usefulness and usability has not been followed by many of the later standards.

This is another standard that rates reasonably highly on my arbitrary value-for-money index, coming in at around 65%.

There are quite a few improvements to be made but there is no doubt BS 1341 will remain one of the better product standards for natural stone.

Reference:

BS EN 1341:2001 – Slabs of natural stone for external paving – Requirements and test methods. Published by the British Standards Institution, London, England.

Barry Hunt is a Chartered Geologist and Chartered Surveyor who has spent 20 years investigating issues relating to natural stone and other construction materials. He now runs IBIS, an independent geomaterials consultancy undertaking commissions worldwide to provide consultancy, inspection and testing advice. Tel: 020 8518 8646

 www.ibis.uk.net