RAINWATER MANAGEMENT


tanks or controlled discharge systems. This allows designers to tailor solutions to site- specific conditions while still achieving SuDS objectives.”


He explains that one of the most significant benefits of concrete block permeable paving is its ability to reduce reliance on conventional drainage infrastructure. Traditional drainage systems often require extensive networks of gullies, pipework, inspection chambers and attenuation structures to manage surface water runoff. These components add cost, complexity and maintenance obligations throughout the life of the development.


“By contrast, permeable paving incorporates drainage and storage functions directly into the pavement structure itself where it is attenuated and reduced in volume due to its ability to intercept and absorb the first 5mm of a storm event. The result is no discharge from the outlet of the pavement. Roads, parking areas and public realm spaces effectively become part of the SuDS management train, providing distributed storage across the development rather than concentrating water within isolated drainage features.”


At Marshalls, Pete Tamblin, head of design & engineering, Marshalls Civils & Drainage, says that for many years, SuDS were largely viewed as a planning requirement rather than an on- the-ground priority. “You’d see them appear in design proposals; they’d support planning applications and help satisfy surface water management requirements. But too often, as projects progressed, their implementation became diluted,” he explains. “Today, that position is changing.”


Growing pressure on sewer networks, increasing scrutiny and the push towards more sustainable development are driving greater implementation of SuDS across residential, commercial and public realm projects. He says that for builders’ merchants, it means that as demand for SuDS solutions continues


Brett Landscaping: Invicta Flow Onyx Pearl Harworth Catcliffe


to grow, they’re increasingly being asked to supply not just individual products, but the components that form part of a complete surface water management strategy. “Historically, many drainage requirements centred around moving water away from a site as quickly as possible. SuDS? That’s a very different approach. Rather than simply conveying rainwater into the wider drainage network, the purpose of SuDS is to manage water right where it falls. Water is slowed, filtered, stored and released in a controlled manner, helping reduce pressure on drainage infrastructure while improving water quality and reducing flood risk,” Tamblin explains. “As such, customers are looking beyond conventional drainage products; they’re seeking integrated solutions that can perform multiple functions as part of a wider drainage strategy. As specifications evolve, products such as permeable paving, soak aways, rain gardens and swales are becoming more common requirements across a growing range of projects.”


The treatment train


Brett Martin’s Stormcrates : designed to meet the needs of modern SuDS


One of the most important concepts within SuDS is the treatment train, yet it remains one of the least understood. Tambiln says this refers to the process of managing surface water through multiple stages. These stages may include source control, filtration, attenuation, storage and controlled discharge, with each component performing a specific role. “The challenge is that many customers still look for a single product capable of solving every drainage requirement. In reality, effective SuDS design relies on several connected elements working together,” he explains, adding that understanding this principle can be invaluable for merchants when supporting customers. “Recognising how products interact within a SuDS system enables merchant teams to offer greater support while identifying opportunities across multiple product categories.”


Tamblin too sees real benefits with 42


permeable paving, which he says is still viewed by many as a surface product. “The reason why is fairly obvious. But within a SuDS scheme it performs a much wider function. Effective permeable paving can provide source control, water quality treatment and attenuation within the pavement structure itself. By managing rainfall where it lands, it can reduce peak flows and help minimise the demand on downstream drainage infrastructure.”


He says that, rather than being treated solely as part of a landscaping specification, permeable paving should also be viewed as engineered drainage infrastructure. “This unlocks opportunities for merchants to support customers with a broader range of complementary products while helping them achieve both aesthetic aspirations and drainage objectives.”


Smarter drainage


Brownfield sites account for a significant proportion of development activity across the UK – but they bring with them a range of drainage challenges: existing drainage networks may be ageing or damaged; ground conditions can be contaminated; available discharge points may be limited. In many cases, extensive hard standing has already reduced natural infiltration opportunities.


Tamblin says that these constraints often make traditional drainage approaches more difficult and costly to deliver, but that SuDS can help overcome many of these challenges by distributing storage, treatment and flow control throughout a site rather than relying on a single drainage solution.


“For merchants supplying projects on brownfield developments, this can mean greater demand for a wider range of products and systems. Customers may need solutions that can work around existing services, minimise excavation or provide surface-level water management without extensive below- ground infrastructure,” he says. The importance of product knowledge cannot be underestimated in areas like this,


www.buildersmerchantsjournal.net September 2026


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