Rethinking space in high-density buildings

The UK’s shift towards higher-density development is no longer a trend, it is a necessity. Continued housing demand, ambitious construction targets, and limited land availability are all contributing towards the growth of tall buildings in city centres, bringing new challenges for architects, developers and contractors alike.

Nowhere is this more evident than in London, which, according to the London Assembly, has four times the national average of high-rise homes.

One in nine homes in London is in a building with six or more storeys, and more than half of homes built in the capital since 2002 are flats or apartments in high-rise buildings. And this is before you consider leisure, hotels and commercial properties. Around 270 tall buildings – of 20 stories or more – have been built over the last decade in London, with another 58 schemes in planning that include at least one tall building.

While much of the discussion around tall buildings is rightly on building safety and energy performance – particularly since the introduction of the Building Safety Act – one often overlooked factor in densely populated buildings is the space required for building services.

Hotels and residential developments are typically designed to maximise returns, but key services infrastructure, such as drainage, can impact the number of rooms/dwellings – not to mention the quality of living for occupiers – if they are not considered appropriately.

The hidden spatial challenge

This is because conventional drainage systems in high-rise buildings generally require a lot of space for pipes, relying heavily on vented stacks and multiple pipe runs.

A typical system will need to allow for d160 pipes and additional secondary ventilation pipes with d90. There also needs to be enough space below ceilings for horizontal pipes to have the correct slope to meet the required discharge capacity. In high-density developments, the cumulative impact becomes significant.

Each additional pipe, offset or vent not only takes up internal space but can also introduce design constraints. Architects may be forced to adjust layouts, reduce net-to-gross ratios or compromise on apartment configurations to accommodate services.

In practical terms, this can mean fewer units per floor, reduced saleable or lettable space, and increased complexity during construction. In an environment where margins are tight and land values are high, these inefficiencies quickly add up.

Designing for density

To address this, manufacturers and building designers are increasingly working together to consider space-saving drainage strategies.

Hydraulically optimised drainage systems, such as Geberit’s SuperTube, are now available, which require less room by creating a continuous column of air within the discharge stack– removing the need for parallel ventilation pipework. The stack can achieve high discharge capacities even when using smaller diameter pipes – and without any additional secondary ventilation. What’s more, horizontal pipes can, in some cases, be installed without a slope for several metres, depending on system design.

This innovative approach, which is the result of significant research and development by hydraulics specialists, can significantly reduce the number of pipes required, reduce the vertical space needed below floors, and create more usable living space as a result. It also reduces material usage and simplifies installation, both of which are vital in an era where project teams are working hard to cut time, save money and minimise raw materials.

Such systems can also be faster to install and require less maintenance than conventional approaches, ensuring project cost savings in the long run.

Balancing performance and compliance

Of course, any space-saving solution must not come at the expense of performance. High-density buildings place significant demands on drainage systems, from increased flow rates to stricter acoustic requirements – with additional standards common across high-specification developments.

In the UK, drainage design must comply with Building Regulations, including Approved Document H, as well as standards relating to fire safety, acoustics and structural integrity. It takes significant engineering experience and robust testing procedures to deliver the right combination of spatial efficiency, robust hydraulic performance and confidence in compliance.

Maximising space in high-density buildings is not the sole responsibility of any single discipline. It requires early collaboration between architects, engineers, developers and manufacturers to ensure that drainage – and building services more broadly – are integrated into the design from the outset. Early coordination can unlock significant efficiencies, allowing project teams to take advantage of the latest technologies and optimise layouts.

Looking forward

Demand for higher-density developments shows no sign of waning and the pressure on space will only intensify. Tall buildings are becoming more complex to satisfy stringent safety requirements, and expectations around quality, sustainability and performance are rising.

Against this backdrop, drainage design is emerging as a critical factor in delivering efficient, effective and viable schemes. By adopting innovative, space-saving solutions and integrating them early in the design process, the industry can unlock valuable floor area without compromising on functionality or compliance.