Apart from temporary measures for social distancing, the pandemic has accelerated implementation of issues raised in the past but put on the back-burner. They include ‘active travel’ (walking, cycling and the ‘15-minute neighbourhood’), ‘low-traffic neighbourhoods’ (reflecting previously-adopted home zones) and reinvention of the high street (responding to the growth in online shopping), writes Chris Hodson, Architect and Consultant to Interpave.
However, a range of wider concerns centred on climate change also need to be addressed in an integrated approach, such as flooding, watercourse pollutants, carbon reduction, air pollution and urban overheating. Measures to deal with these issues are now being implemented by local authorities in planning policies and masterplans.
Replacing temporary measures
During the pandemic, local authorities acted quickly with temporary measures for cyclists and social-distancing pedestrians, manifested with a sea of cones, barriers, road closures and surface planters. Inevitably, these measures were far from ideal, and many have proved unpopular. Hurriedly-widened footways with upstand kerbs running along the centre are just one example.
Understandably, there was a reluctance to commit to expensive and disruptive permanent changes which may take some time to implement – perhaps years – and quickly become outdated. Now, a more flexible approach is anticipated with permanent but adaptable paving solutions, applicable both to regeneration and new developments. Adopting the principles of modern methods of construction, factory-produced modular concrete paving offers a solution, delivering a fast, low-cost installation, including limited intervention retrofits.
Significantly, in these uncertain times, layouts can easily be altered and modular concrete paving taken up and re-used to meet changing demands while meeting circular economy criteria. This principle generally applies to all precast concrete block, flag and kerb products. Distinct, modular units and designed variations in colour, texture and shape can break up areas giving visual interest and a human scale not possible with monotonous, formless materials. So, modular concrete paving delivers a unique combination of predictability, safety and accessibility for all, with scope for endless variety in shape, scale, colour and texture to enrich the urban environment creating real places for people.
Sustainable drainage solutions
Urban flooding from rainwater runoff and surcharging sewers is a growing problem with climate change. In response, concrete block permeable paving will become widespread as a uniquely flexible sustainable drainage systems (SuDS) technique. It provides an inherent drainage system with no additional land take for water storage, treatment or conveyance and eliminates pipework, gulleys and manholes – therefore, costing less than conventional drainage and paving.
Essentially, this technology shares the same impressive performance as conventional modular concrete paving products, being slip resistant, durable, strong and sustainable. The difference with permeable paving is enlarged joints, filled with a permeable aggregate, and the materials used below the blocks, which are specifically selected to accommodate water without clogging. Concrete block permeable paving is unlike – and not to be confused with – permeable materials, which behave very differently.
Concrete block permeable paving can be laid level and still avoid puddles and potholes or adapt to slopes. It provides a safe, firm surface for everyone – including wheelchair users and people pushing prams – unlike gravel and other loose materials. It is also the preferred option around trees rather than tree grilles, according to BS 8300-1 (2018).
Gradual supply of clean water
Equally important to flooding is the long- and short-term damage caused by pollutants in surface water runoff to the biodiversity and health of our rivers and streams. The Greater London Authority Road Runoff Water Quality Study concluded that, “London’s roads are harming London’s rivers” and proposed SuDS features to manage runoff pollution from the most damaging roads.
On any trafficked surface, concrete block permeable paving offers a real opportunity to address this significant problem by trapping vehicle pollution from water runoff. As a result of its unique capabilities, permeable paving offers designers the exciting potential of a gradual supply of treated water that can be integrated with landscape design and promotes biodiversity. It also provides clean water at the head of the ‘SuDS management train’, enabling safe, open SuDS features on the surface, downstream.
Sustainable urban regeneration
Another important innovation, particularly for regeneration, is the retrofitting of permeable paving as an overlay making new use of existing, conventional road bases or other hard surfaces below and their embedded carbon. These low-intervention, thin overlays create attractive, safe and sustainable shared surfaces. They can be particularly effective when they supply a gradual flow of clean water horizontally into rain gardens or bio-retention areas with trees and other green infrastructure.
Green infrastructure will be a significant influence on the public realm in future, with more substantial investment in urban tree planting just announced by Government, supported by planning policies. For example, the July 2021 National Planning Policy Framework states that: “Planning policies and decisions should ensure that new streets are tree-lined and that opportunities are taken to incorporate trees elsewhere in developments.”
However, measures need to be put in place to nurture and allow trees to mature, generally for decades, enabling them to actually deliver their real potential – including net-carbon storage, urban cooling through shading and evapotranspiration, biodiversity and public wellbeing. So, the NPPF also requires that: “Appropriate measures are in place to secure the long-term maintenance of newly-planted trees, and that existing trees are retained wherever possible.”
Paving and trees in harmony
Local planning authorities will now need to incorporate long-term tree maintenance measures in their planning consents. Here, permeable paving, providing irrigation and essential air to growing tree roots while avoiding surface damage by roots, offers a straightforward spatial solution. Although urban trees and paving have traditionally conflicted, this is not the case with concrete block permeable paving, which works in harmony with green infrastructure.
