RIP British masonry product standards

NBS Technical author, Kevan Brassington, outlines the confused transition – now at an end – from BSs to BS ENs for masonry units.

1 July 2007 was a momentous day for the clay brick industry and specification writers – BS 3921 was withdrawn and BS EN 771-1 became the sole product standard for clay bricks, or clay masonry units as the European standard would have it. The demise of BS 3921 was a protracted affair, unlike the relatively quick deaths of cousins BS 4721 (ready mixed building mortar) and BS 5838-2 (dry pre-packaged mortar mixes), which both passed into standards heaven on 1 January 2005 when they were succeeded by the current masonry mortar standard, BS EN 998-2.

We knew at the beginning of the millennium that all our British masonry standard friends were doomed. The publication of the first of the 771 series, BS EN 771-6 Natural stone masonry units, on 15 March 2001 was easy to swallow as no existing British standards were declared as ‘coexisting’ for the planned ‘harmonization’ period of 21 months (the period before the required withdrawal of conflicting national standards).

The victims

We had to wait two months to learn of the first victims. The publication on 15 May 2001 of BS EN 771-2 Calcium silicate masonry units and BS EN 771-4 Autoclaved aerated concrete masonry units (better known as aircrete blocks) announced that BS 187 Specification for calcium silicate (sandlime and flintlime) bricks, BS 6649 Specification for clay and calcium silicate modular bricks, BS 6073-1 Precast concrete masonry units – Specification for precast concrete masonry units and BS 6073-2 Precast concrete masonry units – Method of specifying precast concrete masonry units would be withdrawn in January 2003.

Withdrawal dates are always described in the forewords to standards as ‘approximate’. However no withdrawals were announced in January 2003 and, surprisingly, on 29 September 2003 a new version of BS EN 771-2 was published with a revised withdrawal date of January 2005 for BS 187 and BS 6649. The following day a new version of BS EN 771-4 was published. It included a revised withdrawal date for BS 6073-1 of April 2005 and withdrew BS 6073-2 as a conflicting national standard. So BS 6073-2 was reprieved and remains current and unthreatened by European standards to this day, but why the disparity in the revised withdrawal dates? Perhaps it had something to do with the publication on the same day as the new BS EN 771-2 of BS EN 771-1 Clay masonry units, which announced the withdrawal of BS 3921 and confirmed the withdrawal of BS 6649 as January 2005.

The next in the 771 series, BS EN 771-3 Aggregate concrete masonry units (Dense and light-weight aggregates), was published on 17 March 2003. It gave coexisting BS 6073-1 a further reprieve until September 2005. The series was completed on 18 March 2004 with the publication of BS EN 771-5 Manufactured stone masonry units. It condemned BS 6457 Reconstructed stone masonry units to oblivion in September 2005, but failed to recognize the existence of BS 1217 Specification for cast stone as a conflicting national standard.

NBS updates

NBS Building update 40 (November 2004) included a revised version of F10 Brick/ block walling with dual clauses, allowing the specification of masonry using either British or European standards. Keen F10 watchers will remember the inclusion of a table in general guidance summarising BS EN publication dates and proposed withdrawal dates for coexisting standards (see also NBS Journal 05). The table was updated in August 2005 as part of update 44 and was brought up to date last month for the current update. It is included here to show the latest situation and to illustrate the frustration NBS technical authors feel when, having completed and finalized a work section, they discover new information that materially changes the work they have just done. Checking the BSI online website at the end of September, we find that the remaining masonry standards BS 187, BS 6649 and BS 6457 will be withdrawn on 1 October, too late for inclusion in update 2007-3.

The remaining loose end is the required revision to BS 1217 Manufactured stone masonry units, to remove the specification content that overlaps with BS EN 771-5. The conflict with BS 1217 was initially overlooked when BS EN 771-5 made its first appearance, but the omission was rectified with the November 2005 amendment.

The change from British to European standards for masonry products is now effectively complete and marks a move from prescriptive to performance standards, where the specifier needs to decide what the manufacturers’ declared property values really mean for the intended application. The onus is now even more focused on the specifier making the right choice and that’s where NBS guidance can be your best friend.