An architect’s guide to the best rainwater drainage materials

Posted by judy


There is no shortage of materials to choose from these days when you’re designing drainage systems for commercial and residential properties. The products you choose will depend on a range of factors, including your clients’ budgets, their style preferences and their practical needs. Issues such as planning rules can also have an impact.

Three of the best and most popular rainwater drainage materials currently on the market are aluminium, cast iron and steel, and here is a brief guide detailing the major benefits of each.


Aluminium just so happens to be the most abundant metal on Earth, and it is now widely used in the production of drainage materials. It is loved by designers for its high strength to weight ratio, which makes it perfect for building projects. Because gutters and downpipes made from the material tend to be relatively light, they are generally easy to fix to walls and roofs. The metal is highly flexible too, making it easy to shape. This is useful if you are planning elaborate or unusual drainage systems.

The metal is highly resistant to corrosion as well, which is, of course, a must for rainwater systems. In addition, it can be finished in a selection of distinct styles to create different looks. Here at Alumasc Rainwater, we offer both heritage and contemporary ranges in a choice of 26 standard colours. Aluminium is also 100% recyclable.

Cast iron

Cast iron has long been used in building projects in the UK and elsewhere around the globe. Until the 1960s, this metal was the most common guttering material, and it’s not hard to understand why. Cast iron is extremely robust. Even with only rudimentary maintenance, such as a scrape with a wire brush and a new coat of paint every decade or so, it can last for a century or more. While these solutions may come with higher price tags than other rainwater systems, their impressive longevity means they can prove to be a cost-effective option in the long term.

In addition, because of its strength, the metal has a high resistance to impact and vandalism. This can be especially important in cities and on buildings that are at particular risk of damaging weather events, such as strong winds, heavy snowfall and hail. Furthermore, thanks to its rigidity, the metal can comfortably withstand the weight of ladders when maintenance is carried out.

Cast iron gutters are also unlikely to rattle in the wind and they offer excellent sound deadening properties, meaning any noises caused by running or dripping water are negligible. This adds to their sense of luxury.

However, it is in terms of aesthetics that cast iron really stands out. It has a majestic look that most other materials struggle to match and it can significantly enhance the appearance of a building. It is also perfect for historic and restoration projects.


Another great option is steel. Like aluminium, this is a lightweight metal and it can be durable and low-maintenance. It is also eco-friendly and it offers a cost-effective alternative to plastic gutters, without the risk of leaking, colour fading and shrinking.

We offer steel drainage systems in both a galvanised and a black pre-coated finish. Alternatively, if you’d prefer a different look, you can take your pick from six other galvanised pre-coated colour finishes.

Quality and care

Of course, whichever material you select, you’ll need to make sure you opt for top-quality products. For the best results, your drainage systems must be designed and built to the very highest standards. Also, all drainage solutions require a certain level of care, and you must ensure that property owners are aware of this when you are discussing their options with them.

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