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RCI December 2017

Zink INDUSTRY NEWS LETTERS 01992 801927 www.almhm.co.uk 010 DECEMBER 2017 RCIMAG.COM Copper Stainless CITB future strategy Dear Editor The Metal Cladding and Roofing Manufacturers Association (MCRMA) was surprised or perhaps even shocked at the recent announcement by the Construction Industry Training Board (CITB) chief executive, Sarah Beale, that the CITB is to end the delivery of direct training and step back from operating its National Construction College sites as part of a “bold new strategy” for its future offer. The Government is at long last emphasising the need to drive a construction strategy and one would have assumed that this would have resulted in the need to provide training for new starters within the industry and offer upskilling courses for those who are vital for its future success. One would have also assumed that the word ‘training’ in the acronym CITB would have been a clue to its primary role within the industry. The MCRMA has for many years operated introductory courses in roofing and cladding for new starters across member companies and the courses have been well attended and well received. However, we consider the future training of site operatives and supervisory staff should sit firmly within the operational scope of the CITB and it is vital that the important tutors and training facilities are not lost and that training itself is not downgraded. The MCRMA would suggest that CITB should urgently review this recent announcement and consult directly with the Associations who consider this proposal to be a big step in the wrong direction. Yours sincerely, Carlton J Jones Director Metal Cladding & Roofing Manufacturers Association Dear Editor I would like to comment on Janet Chadbone’s letter and John Mercer’s reply: The concrete roof tile industry has dominated domestic roofing since World War 2 and has done so by being the most competitive, including the reduction of components to their cheapest form. This has included the self-weight of tiles and fittings which was the previous method of resisting winduplift of tiles. British Standard Code of Practice CP142 was found wanting in 1976 when the extreme gale occurred over the North of England, particularly over Sheffield, resulting in considerable property damage. CP142 was urgently revised to provide advice regarding fixing tiles and the concrete tile industry provided the lead by introducing wind-tunnel testing and complicated fixing specifications to overcome the difficulties arising from the diminished self-weight of components. The BS 5534 committee was mainly made up of manufacturers’ representatives, salesmen, as well as technicians and scientists. There were no craftsmen on the committee and I was invited by the NFRC to attend meetings (as an unpaid volunteer) in 1977, continuing for over 25 years! The amended document was well advanced when I first attended and there was much to be done to accommodate the roofing craftsman’s interest. However, the technicians and scientists gave me a good hearing and the revised code of practice was published in 1978. Standard practice was to use cement mortar in the assembly of concrete tile roofs to increase the self-weight by bonding the assembly together, relying on the bonding tensile strength of the mortar. With single-lap tiles various clipping arrangements were introduced to satisfy wind-tunnel testing. Until the very recent ‘ban the mortar campaign’ you will find it hard to find a concrete tiled roof that does not depend on cement mortar for security. This is not surprising as tiled roofing has always been a trowel trade. Marley Eternit Uncovered p20, RCI Nov ‘17 Competition on tile prices is such that the manufacturers depend on enhancements to increase margins. Some of these have been welcome but other are less wise and with single-lap tiles being of proprietary design; related specials should not be part of a code of practice. The manufacturer is responsible for fixing design. Responsibility cannot be passed off to a generic design. The tensile strength of mortar is a fact which cannot be denied. With the introduction of masonry mortar which is only intended to have compressive strength, and with its delivery in quantity to building sites the inevitable happens and the required additional cement gets missed out. The mechanical fixing craze has taken advantage of this failure to use proper tensile strength cement mortar. The lightweight segmental concrete ridge tile has always required a good cement mortar bonding bed and examples are everywhere. The biggest danger comes from the separation fluid used by the manufacturer to stop the tile sticking to the moulds. If left active it also stops the tensile mortar from sticking to the tiles. The attached photo is an example. The settlement that John Mercer refers to should be designed out, particularly where roof trusses settle against brickwork. Purlin and rafter construction did not suffer this problem. Yours sincerely, Gerald Emerton (retired), author of ‘The Pattern of Traditional Roofing’ Send your letters to the editor: matthew.downs@markallengroup.com Concrete thoughts “The biggest danger comes from the separation fluid used by the manufacturer to stop the tile sticking to the moulds. If left active it also stops the tensile mortar from sticking to the tiles” Dear Editor The above feature on Marley Eternit, which talks about BS 5534 graded battens, contains a couple of statements that are somewhat misleading or inaccurate. It says that BS 5534 doesn’t actually state how or where the battens should be graded, as though that is an issue: but no grading standard ever states that. Of course, a factory is the obvious place to do grading; although an importer’s yard would also be good, provided that there were trained graders doing the grading; after all, the rules in BS 5534 are intended for the visual assessment of battens by a trained grader, in any case. However, Marley Eternit say that their laser and camera scanning is able to produce “the most accurate and consistently graded battens”. But in fact, the scanner which produces JB Red has no greater potential for accuracy than a well-trained human grader: and I have personally checked parcels of both laser-scanned and “human” visually graded material; and I found that they both gave around 95-98% accuracy from either method. (I have been a member of the UK Timber Grading Committee for about 30 years). Although that article repeats many of the rules given in BS 5534, it does not emphasise the main point strongly enough – that a graded batten must have the number of the standard stamped on it; and that any other “BS” numbers (such as the preservative treatment standard, BS 8417) are not needed: and if that last number is the only BS number that appears on a batten, then it is not a graded batten. And that is really all that needs to be said on the subject of misleading marking. Finally, the article does not mention anything about 3rd-party QA marking, which is the best way for roofers and inspectors to be sure that their battens are up to grade. And, whilst such marking is not a specific requirement of BS 5534, it is an obvious way for users to have confidence in the battens that they are using. Yours faithfully, James C Coulson Director, TFT Woodexperts


RCI December 2017
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