CODES OF PRACTICE (MASONRY & PAVING)
All three parts of BS 5628 ‘Code of practice for the use of masonry’ are available from BSI Publications Sales.
‘Structural use of unreinforced masonry’ attempts to align the standard with appropriate BS EN standards. BS 5628-1:2005 was published in December 2005.
‘Structural use of reinforced and pre-stressed masonry’. BS 5628-2:2005 was published in December 2005.
‘Materials and components, design and workmanship’ incorporates a new version of BS 8000: Part 3: ‘Workmanship on building sites – Code of practice for masonry’ (also available separately). BS 5628-3:2005 was published in December 2005.
Amendments to all three parts of BS 5628 ‘Code of practice for the use of masonry’ brings the suite right up-to-date and maintains the economy and efficiency of masonry design and construction.
Under normal circumstances revisions to the code would have been published several years ago, but for about ten years publication of new and revised British Standards has been subject to delay, in favour of drafting new European standards in association with the European Committee for Standardization (CEN). The European standards for masonry design and construction are now available. Each part is published with a National Application Document enabling it to be used in the UK. Designers may now choose to use these standards as an alternative to BS 5628, which covers the same subject matter, but is not directly comparable to the European standards in detail.
BSI technical committees have, however, continued to monitor the BS national codes. They have reviewed changes to safety and other aspects in order to bring the recommendations up-to-date and also to provide consistency between emerging European and existing British codified guidance.
BS 5628: Part 3: 1985 and BS 5390 are superseded by BS 5628-3:2005.
The new document updates all cross references to Standards, Technical Approvals and authoritative guidance relating to masonry units, mortars and ancillary components and materials. Major sections of content are particularly related to brickwork, but BS 5628: Part 3 covers all masonry including blockwork and natural stone masonry (formerly dealt with in BS 5390, which has now been withdrawn).
There are no major changes to recommendations for the accommodation of movement, but instead is set out with greater clarity and now includes guidance on short returns in walls.
Notes are included on movement provisions specific to masonry cladding to timber, steel and reinforced concrete frame structures. Examples of cladding support systems reflect modern concerns to minimise cold bridging and maintain continuity of insulation.
Guidance has been developed with the benefit of building performance research and meteorological data gathered since 1985. Exposure Categories have been simplified. Considerable experience with cavity insulated walls since 1985 is reflected in recommendations for the inclusion of partial and full-fill insulation.
DPCs and Trays
General principles are noted. The complications involved in providing waterproofing, where flat and sloping roofs abut cavity walls are shown, as are details of waterproof trays and flashings to chimney stacks penetrating roofs.
The advice on mortars has been extensively reviewed. Mortar mix design developed at the BRE incorporating lime and air-entrainment to improve mortar durability is included. The Code only covers with Portland cement based mortars and does not address the use of natural hydraulic lime and sand mortars.
BS 5628-3 includes a section on workmanship, because it is a crucial factor in achieving good quality masonry, particularly brickwork. BS 8000: Part 3: ‘Workmanship on building sites – Code of practice for masonry’ was first published in 1989 and dealt with the subject more extensively than in the 1985 edition of BS 5628: Part 3. To avoid possible ambiguity it was decided to revise BS 8000: Part 3 and include the complete new text in the revised BS 5628: Part 3 as Annex A.
Because many users only require the Workmanship standard, the revised version of BS 8000: Part 3 was also published in August as a separate document. Reference and Rules
With the 1985 version of BS 5628: Part 3 the BSI technical committee set out to provide more than a minimum set of rules for effective masonry. It provided the rules, but also elaborated on the technical rationale. In doing this it indicated alternative solutions to design and specification problems.
The ‘textbook style’ content of the Standard is widely appreciated and the publication has become a well-used reference. The new edition continues in this helpful tradition, being readable and informative.
Structural Codes Amended
An amended version of BS 5628-1, ‘Structural use of unreinforced masonry’, was published by BSI in 1992. It contains a number of important changes including updated wall tie provisions for cavity walls allowing cavity widths up to 300mm; revised lateral wind load design that improves the economics of masonry cladding panels; and amended guidance on the assessment of loading factors for earth retaining structures so as to be compatible with BS 8002: ‘Code of practice for earth retaining structures’.