Context 152 - November 2017

C O N T E X T 1 5 2 : N O V E M B E R 2 0 1 7 13 Floorscape Traditional paving was laid as a ‘flexible pavement’, with the stones or bricks bedded in sand or grit, and sometimes pointed with tar.The design worked well with traditional traffic: horses, carriages and wagons, which tended to drive the setts into the bedding, helping to consolidate them, and the iron-shod hooves and wheels, which would wear them smooth. Modern traffic causes very little surface wear, but applies very high sideways forces, which can rotate or dislodge the setts. A further challenge is from street-sweeping vehicles, which in the UK vacuum rather than sweep.The suction draws out the bedding material in which the setts or flags are laid, destroying their stability. In continental Europe the street cleansing machines are much more likely to be limited to sweeping only. Such machines create less dust, which may benefit air quality. There may be heavily trafficked areas where traditional flexible laying methods are unsuitable. Here the setts must be bound together as a rigid surface with a high- strength mortar, laid on a steel-reinforced concrete foundation. It is also possible to limit the weight of vehicles to protect the surface. Traditionally, gaps between slabs and setts were narrow. Today when paving is relaid the width is often increased inappropriately. In some examples there is more mortar than stone.Wide joints create a surface that looks ugly and is uncomfortable to walk on. Mortar spread over the surface of setts or flags can take several decades to wear off. Such work should be condemned and the mortar chemically removed. It is almost impossible to paint white or yellow lines on sett paving without the paint spreading and creating an embarrassing eyesore.There may be no need to use lines at all. Government has suggested using restricted parking zones in preference to painting yellow lines.The Traffic Signs Manual provides guidance on this. Some streets are so narrow that any parking would materially obstruct the way: obstruction of the highway is an offence under s137 of the Highways Act 1980. In these streets it is appropriate to ask whether the additional traffic orders are necessary. If lines are deemed necessary, they should be the narrowest available under the Traffic Signs Regulations and General Directions (that is, 50mm and not 100mm).The TSRGD only requires lines to be yellow, not chromium yellow. White centrelines have been shown to increase vehicle speed: they can be dispensed with altogether. Parking spaces can be delineated with studs. Sometimes utility companies excavate traditional paving and reinstate temporarily using bitumen, taking the excavated material to landfill.The permanent repairs are then undertaken using setts of a different size, finish and type of stone, leaving a permanent scar. Different stone types are often mixed inappropriately, or arbitrarily sourced types of stone are introduced that were never used locally or are being used in non- traditional ways. It is important to record what materials are used in a street and why.Without this knowledge it will be difficult to maintain the street’s distinctiveness. Granite setts andYorkstone flags are often regarded as Visitors are unlikely to trip at RomanVindolanda (below) because the paving is clearly uneven, but a single rocking slab can be a real hazard Scoria blocks in Faversham, Kent Carefully detailed new paving in Glasgow (Photo by Richard Guise) The grammar of paving. Drawing by Richard Guise