The Department for Communities and Local Government (CLG) has issued the amended version of Approved Documents A and C. This note summarises the key amendments and provides commentary on the proposed changes.
The document outlining the changes to Approved Documents A and C is available below.
- The potential conflict between the Building Regulations and safety legislation has been highlighted in a new introductory paragraph. Although this may arise in a number of ways, and specifically from the Memorandum of Agreement between Building Control Bodies and HSE, it is perhaps not as helpfully worded with regard to designers as it could be, around whom a strategy has previously been suggested [2,3]. Nonetheless, it is considered that this strategy remains relevant and this revision is an opportunity to impress upon designers the need for a risk managed approach.
- The subsequent amendments mostly relate to the introduction of the Eurocodes as the UK's National Standards. To this end the standards listing now refers to the Eurocodes and the pre-existing standards (e.g. BS8110) are no longer scheduled (and are of course formally withdrawn). CLG are obliged to make this change, however it does not necessarily mean that these standards are unacceptable for use on building regulation submissions (and this is acknowledged in the text). Designers must assess their suitability on case by case basis, although it is important that the two approaches are not mixed.
- The area of structure permitted to suffer collapse, before key elements are required, has been increased to100m2 in line with BS EN1991-1-7. This was expected and better reflects contemporary building construction.
- Despite the new introductory paragraph mentioned above (para 1), the statement under the disproportionate collapse requirements for Class 3 structures, that it is only these that require a 'systematic risk assessment', is not clarified. It has been outlined elsewhere that the process of risk management is required for all structures [2,3] even though it may be limited for building regulation purposes.
- The requirements for Class 2B also remain unchanged. Hence the industry recommendation for horizontal ties to be provided where possible even if key elements are used  also remains pertinent.
- The UK wind map has been amended to align it with the Eurocodes national Annex.
- The minimum depth in clay has been expanded to cover a range of conditions.
- Although sezmic design is not often required for buildings in the UK, Approved Document A does make reference to it. However the wording of the inserted paragraph (new paragraph 5.5) does not accord with that of the relevant Eurocode (BS EN1998-1); this states in its foreword:
'There are generally no requirements in the UK to consider seismic loading, and the whole of the UK may be considered an area of very low seismicity in which the provisions of BS EN 1998 need not apply. However, certain types of structure, by reason of their function, location or structural form, may warrant an explicit consideration of seismic actions.’
This is considered an improvement on the Approved Document wording and gives emphasis again to the need for a risk-assessed approach for all structures [2,3].
- The requirements for fixings (applicable to cladding) remain unchanged. It had been suggested that this become a more generic title, applicable to cladding and other structural situations. This suggestion arose as a result of concerns by SCOSS at the lack of attention often paid to structural fixings. A number of items on this subject will be found on the Structural-Safety website.
- Harding G, Carpenter J. Disproportionate Collapse of Class 3 buildings; the use of risk assessment. The Structural Engineer August 2009
- Carpenter J. The systematic risk assessment of UK Building Regulations class 3 structures. Structures and building Journal Institution of Civil Engineers February 2013
- Practical guide to structural robustness and disproportionate collapse in buildings. Institution of Structural Engineers October 2010