BS449 v. BS5950
In the past we have occasionally been contacted when an over-zealous building control officer has told a SuperBeam user that calculations to BS449 are no longer acceptable and BS5950 should be used instead, especially following the introduction of a revised Part A Approved Document in December 2004.
Whilst having a long overdue purge of old magazines and papers I came across this announcement on p.28 of BSI News, August 1992:
"Following the widespread concern over the proposal to declare BS 449: Part 2: 1969 'obsolescent', Sub-committee B/525/31 (formerly CSB/27) has decided not to proceed further with the implementation of this action at this time and the standard maintains its present status.In coming to their decision, the members of Sub-committee B/525/31 were mindful of the fact that BS449: Part 2: 1969 continues to be used by engineers and is a standard referred to in Approved Document A to Building Regulations. The Sub-committee conforms to the policy view of BSI that its future work lies with the development of Eurocodes and supporting standards."
- 15+ years on, the definitive Eurocodes and supporting National Annexes have finally been published, whilst BS449 Part 2 is listed in the BSI catalogue as "current, proposed for confirmation, partially replaced" - £190 (!!) (July 2009) if you're not a BSI member! BSI catalogue
In the 2004 Part A Approved Document (available as a free download from the Planning Portal web site, BS449 is no longer listed as an approved code. Replacing BS449 with BS5950 within SuperBeam would mean that in many cases (e.g. a loft conversion ridge beam bearing on a timber post) limit-state and permissible stress calculations would be intermixed in the same set of calculations - something less than desirable. When we pointed this to ODPM (as was), their response was to confirm that the fact that a code does not appear in the Part A Approved Document does not mean that it cannot be used, and that the continued use of BS449 in domestic scale structural calculations would not necessarily be impermissible. To quote the new Part A AD "There is no obligation to adopt any particular solution contained in an Approved Document if you prefer to meet the relevant requirements in some other way".
'Structural Engineer' 15 March 2005, p.38 includes a letter from
Geoff Harding of ODPM: "... Regarding the use of withdrawn Codes,
building control authorities will need to be satisfied that such documents
continue to provide satisfactory guidance for any structures under
consideration. In this context reference should be made to the safety
aspects given in paragraph 0.2 on page 6 of the AD.
In the case of BS449 its recommendations were considerably enhanced by
amendment No. 8 prior to the document being declared obsolete several
years ago. The Code will therefore no doubt continue to provide satisfactory
guidance at least for the design of simple beams and other minor
works.
We are now working on a new program, EuroBeam™, which will ultimately replace SuperBeam and ProSteel and is based on Eurocodes EC3 and EC5 - see our EuroBeam site for more information. The first release is now being made available to SuperBeam and ProSteel users with current update cover.
On 29 January 2010 DCLG issued a letter stating that the Part A Approved Document A is unlikely to be amended until 2013, thus the present AD listing BS5950 (and other codes) as acceptable. Quote:
WHAT THIS MEANS FOR BUILDING CONTROL BODIES (BCBs)
When assessing compliance with the Building Regulations, BCBs should continue to consider the appropriate use of relevant standards on a case by case basis. This may include the use of the new BS ENs [Eurocodes], which formally become the new national standards in April 2010 reflecting the changes made by the standards organisations. There is no need to wait until April 2010.
The British Standards to be withdrawn on 31 March are and will remain available from BSI. But BSI committees have already stopped updating those British Standards, and so they may not necessarily be suitable for aspects of structural design in the medium and long term.
BCBs will need to be aware of the risk of designs inappropriately mixing new design standards based on the BS ENs and withdrawn BS design standards.
Emphasis is ours. Full letter here [PDF]
For now we hope that Building Control checking engineers will continue to accept the use of BS449 for structures such as loft conversions that involve an intimate mix of steel and timber structural elements, and not unreasonable to use this code for simple steelwork calculations in domestic scale structures. For other work we would agree that BS5950, on which our ProSteel program is based, is the better code to use. Registered users of SuperBeam can now buy ProSteel for just £100+VAT. As familiarity with Eurocodes builds it will become increasingly possible to use them with confidence.
