Codes of practice throughout all strands of the construction industry are under constant review to reflect changes in legislation or improve working processes. But in the haste to deliver an increasing volume of building projects to ever-tighter deadlines, are revised standards being overlooked in the charge for the finish line, or do they generally go unnoticed? Steve Ricketts, Branch Manager at BriggsAmasco’s Manchester headquarters, highlights a code of practice change that will serve the roofing sector well – if it is adhered to.
Introduced in December 2018, the BS 6229:2018 code of practice, which describes best guidance in the design, construction, care and maintenance of a flat or curved roof with a pitch not greater than 10 degrees, has a few distinct changes to its original form. The headline amendment as far as specifiers and installers are concerned is likely to be the advice that states flat roofs should be designed with a fall of 1:40 to ensure a minimum 1:80 fall is achieved once the roof and gutter soles are completed. The new guidance, which was four years in the devising, drew a line in the sand. Its evolution is aimed to address the serious issue of flat roof ponding. But as someone who is tasked with assessing roofs across UK construction sites on a regular basis, I’m inclined to think large-scale adherence to the new guidance is lacking, particularly when looking at inverted roof solutions such as hot melt where the system is BBA-certified for a zero falls or flat roof deck.
Dealing with dishing issues
Construction-wise, flat in terms of a roof doesn’t mean totally flat. Concrete decks often have deflections or back falls that form dishes in which water can collect. The revised code of practice acknowledged this issue by putting the onus on designing-out the potential for ponding prior to construction. For inverted roofs where this hasn’t taken place and a concrete roof has acquired negative falls as a consequence, another solution is required. Previously, the simplest way to correct a fall-less roof would be to lay the concrete deck, wait for it to rain and see where the water ponds. In severe cases, additional outlets would then be installed in the affected areas to ensure the water is drained away. But as much of the roofing work carried out by BriggsAmasco in the past couple of years has involved high-rise residential towers, there isn’t the freedom to be selective when installing outlets. This, therefore, negates the option.
Fortunately, there are a couple of other proven solutions when it comes to concrete inverted roofs which fail to meet the revised BS 6229 standard. One method involves laying a screed across an entire roof to form the omitted fall. Flexiscreed or Permascreed is ideal for this action, which in installation terms means starting with a minimum depth of 10mm and ‘falling’ towards an outlet, depending on the shape and size of the roof containing the falls. An alternative option is to infill the ponding indentations and wait for rainfall to evidence where the water lies. The surface can then be levelled back to zero falls. This is a less-costly method and guarantee-wise, will generally satisfy most flat roofing requirements.
Hot melt roofs tend to be the simplest to correct when it comes to inverted flat roofs and the potential for ponding. On surfaces where there is only a small deflection, for example, the hot melt can be quickly and easily built-up to the same level as the remaining roof area. During summer when rainfall isn’t as prevalent, a roof survey is often the quickest and most effective way to confirm that a hot melt roof has been levelled to the required standard.
I believe the revised code of practice is a definite and positive step to reducing issues with ponding on flat roofs, which can have damaging consequences for buildings – if not treated correctly – over time. The fact that a prevalence of inverted roofs are still being built to the 2003 guidance suggests to me a lack of awareness of the revised advice among the building industry as a whole. If standards are to improve and assure our buildings are long-term protected against the elements, perhaps it’s time the roofing industry itself did more to promote the best practice outlined in BS 6229:2018. Metaphorically at least, shouting from the roof tops about this new level of guidance could be what it takes to bring about the change it designs to inspire.