26 BUILDING FABRIC
control. This is not only a quality, but also a serious health and safety concern. The best way to avoid this is to specify a batten by name from a trusted manufac- turer or a full roof system which includes BS 5534 compliant battens.
OVER OR UNDER VENTILATING Either having too little, or too much, ventilation is a common pitfall with roof specification. Inadequate ventilation, i.e. using a breathable underlay as the sole means of ventilation, can cause condensa- tion. However, overventilation can add unnecessary cost. To avoid this, always comply with BS
5250:2011+A1:2016 ‘Code of practice for control of condensation in buildings’ and BS 9250:2007 ‘Code of practice for design of the air tightness of ceilings in pitched roofs’.
isn’t always the case, and we have heard of numerous incidences where non- compliant battens have unintentionally been used and been identified by building
NOT INCLUDING A FIXING SPECIFICATION Often, a fixing specification is not included and is left to the contractor. However, this is one of the most important parts of a roof specification and shouldn’t be left to chance. Some contractors will get a bespoke
fixing specification from a manufacturer, but others may simply fix to the way they have always done. Not only does this
mean the roof may not have enough fixings for the level of exposure, but it also makes it hard to compare prices if contractors are working to different fixing specifications. By including a fixing specification, the housebuilder can reduce the risk of inadequate fixing and ensure they are comparing like with like on price.
REDUCE RISK With all elements of construction coming under tighter regulations, inevitably there will be more scrutiny on roofing specifications. One of the best ways for specifiers to reduce risk is to specify a full, tested roof system, rather than individual components such as tiles or underlays. This helps to minimise product substitution, or use of inferior materials further down the line, and gives a clear line of accountability.
NOT TALKING TO A MANUFACTURER Finally, many issues that occur further down the line with pitched roofs could be avoided if the roofing manufacturer was involved in design discussions earlier on in the process.
Stuart Nicholson is roof systems director at Marley
WWW.HBDONLINE.CO.UK
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