Going tall…New heights for MMC are being reached by a project in Singapore by two 192 metre tall residential towers. There will be 988 apartments arranged over 56 floors, with seven commercial units at ground floor level.
The development is within a densely populated area in Singapore, with limited space for construction. It made sense to use volumetric factory made modules and lift them into place. However, modular units had not been built above 135 metres, which is currently a limitation due to the light gauge steel framing used in each module.
Structural design at such heights is driven by wind loading. Typhoons are rare in Singapore, but can occur and would need to be designed for. The engineers arrived at a solution using lightweight concrete for the module shell. This was light enough to lift to almost 200 metres, but had enough density to stabilise the structure against the wind.
The concrete boxes were formed by a Malaysian manufacturer, then fitted out in an off-site facility in Singapore. This resulted in 3000, 80% finished units being delivered and hoisted into place on site. All the benefits of modular construction were realised, including a reduced site team to maintain Covid 19 requirements.
Upside down…A residential building in Leeds, UK, employed an off-site pre-fabrication system.
Like 'flat-pack' furniture, the floors and walls were manufactured in the factory and shipped to site where they could be lifted in to place.
The building was completed and residents enjoyed over five years in the premium accommodation. It was then realised that the floor panels had been installed in the wrong order, with lower floors at the top and the top floors on the bottom.
The floors were similar, but supposed to reduce in weight on the upper floors. The stability of the building was at risk and failure of the structure could be a total collapse.
Remedial works have now made the building safe and it is fortunate that a disaster was avoided. This highlights a key risk of innovation in construction and there should always be a focus on risk management.
Rushing ahead…From September 2020 the new laws on Permitted Development Rights (PDR) apply. The PDR determine what type of building work can progress without a Planning application.
David Cameron famously extended the length of a house extension from four to eight metres, which increased home extensions in the face of increasing house prices. The government intend these current changes to stimulate construction activity, particularly residential projects, which in turn creates job and fuels the economy. But are they rushing ahead?
The new PDR allow the demolition of vacant office buildings; change of use to convert light-industrial buildings for residential use; and up to two additional storeys can be added to residential blocks built between 1948 and 2018. These types of project no longer require a full Planning application, but can rely on a fast-track approval process.
Voices against the new PDR raise questions of quality of the new residences. Compliance with the Building Regulations will not change and the requirements for conservation of energy and ventilation would still apply. This may be an argument to support 'NIMBYism', as there will be less resistance to new housing developments alongside existing rural villages and towns.
The spirited resistance is based on concerns that the new PDR does not align with our commitments to reduce carbon. This is based on housing sites progressing at full speed, without fitting into the wider development strategy. The Government is currently revising the National Planning Policy Framework (NPPF), which is intended to include provisions to meet our climate change targets. The call is for restraint of the PDR, until the new NPPF is in place.
Based on the best examples of MMC, it would be possible to create new housing at the pace we need, the quality we need and in line with the targets we have signed up to.
We seem to be moving in to a golden age for construction, with technology becoming more reliable and innovation replacing the traditional methods. We can think big, as long as we get things the right way up and don't rush!