CONCRETE & STONEWORK
URBAN PAVING REPOINTING - FOR THE LONG-TERM ! PART 2
‘ Larger Format ’ paving
Larger format paving is generally used to mean slabs / flags larger than 400 x 400mm , such as the traditional 2 ’ x2 ’ ( 600 x 600mm ) and 3 ’ x 2 ’ ( 900 x 600mm ) in classic Yorkstone ( a durable naturally dense sandstone quarried in Yorkshire ), and then more recently , the 20th Century ‘ classic ’ precast concrete flags that have been and are widely used for pedestrian pavements in urban areas all over the UK .
With larger format paving slabs or flags ( basically the same thing - depending on where you live in the UK ), the need to ensure a uniform bed is clear , as any voids or high-points would lead to poor levels and trip hazards , as well as voids resulting in serious damage in service . Urban paving slabs / flags were and are generally 2 ” ( 50mm ) thick , rather than the 20-25mm now typical for domestic paving , and the joints are typically specified at a nominal 5 to 12mm wide . Whilst paving jointing is always important for many reasons , for larger format paving , the ratio of joint surface area and volume to the paving elements surface is very low ; any lateral movement or stress on the joints , including overall thermal movement , will also be limited for the same reason . Therefore larger format paving should not generally be used for heavy vehicular trafficked areas without special measures , e . g . using thicker slabs and wider joints .
‘ Smaller Format ’ paving
Smaller format paving means paving units or blocks , such as cut natural stone setts , which are less than 400 x 400mm , typically these are the traditional 4 ” x 4 ” ( 100 x 100mm ) and 8 ” x 4 ” ( 100 x 200mm ). This type of smaller format paving also has different names , they can be called known as setts or cobbles in different regions of the UK . Natural stone paving purists may regard stone setts as being ‘ quarried and cut ’ natural stone with 6-defined sides . Whereas they would consider cobbles to be naturally occurring , water or otherwise eroded over time , and therefore these are generally round edged , more variably dimensioned , natural stone elements , e . g ., taken from natural sources at the bottom of glaciers , rivers , and beaches - Although these are also now being manufactured mechanically . However , to be correct and in accordance with BS EN 1342:2001 : “… a sett is a dressed block of stone having plan dimensions that are 50-300mm in length , and a thickness of at least 50mm . The length and / or width should not usually be greater than twice the thickness .”
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