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At Portsmouth SIPs modules were used to add top-floor apartments

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Structural insulated panels unlock high-volume house targets

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Developer-constructor Low Carbon Construction plans to build 10,000 affordable homes a year using its modular SIPs system. Owner Simon Allso explains his ambitions and his thinking to Will Mann.

For a new developer to target building 10,000 affordable new homes a year is ambitious. To do this using modular and eco-friendly methods takes this ambition to even greater heights. But that’s the goal of Simon Allso, owner of Hampshire-based Low Carbon Construction (LCC), a developer-constructor which focuses chiefly on new-build affordable housing.

The company uses a modular building system, based on structural insulated panels (SIPs), which was devised by Allso in 2010.

“I wanted to work with lightweight materials that could be used for volumetric construction,” he says. “The Hemsec SIPs can be used for floors, internal and external walls (loadbearing and non-loadbearing), and are up to 6m long so can create double-height spaces. We can create flat or pitched roofs, the advantage of SIPs being that they create an open roof void in pitched roofs as we don’t need trusses.

“We can use the SIPs to create any bespoke modular building, and have done schools and commercial buildings, but our focus is on affordable housing.”

Allso initially set up a modular factory in Portsmouth. But after a strategy reappraisal, he closed it in 2015, deciding the future lay in smaller scale onsite assembly plants.

“Fixed factories restrict volume house-building,” he says. “They put a cap on output, and are also not environmentally sound, as the homes manufactured have to be put on a low loader and transported to the housing development. Instead, we have localised factories on site. It is a scalable model, so we could have 1,000 sites and 1,000 factories.”

Structural insulated panels used by Low Carbon Construction

  • Maximum dimensions 1.2m by 6m   
  • External and separating walls 175mm thick, internal walls 100mm thick    
  • Faced with 15mm oriented strand board (OSB) grade 3
  • Polyurethane insulation core
  • Maximum weight 25.5kg/m2
  • U-value of 0.18W/m2k
  • CE, BBA and BM Trada certified

Projects to date have included small-scale schemes, such as an extension to a three-storey art deco building in Portsmouth, where 20 SIPs modules were craned in to create an extra floor of nine 70 sq m apartments. Its biggest development to date is for 850 homes at Parc Emlyn near Llanelli, ranging from one-bedroom apartments to five-bedroom detached houses. Allso’s ambition is to tackle mostly larger schemes of “100 to 150 units upwards” to give economy of scale for the factories.

“The factories are demountable and reusable, built from SIPs and a steel frame, and sited on piles,” he says. “They are 10,000 sq ft to 15,000 sq ft [930-1,400 sq m] in area and can be erected in five days.”

The onsite-offsite factories, as Allso calls them, assemble components from LCC’s 58 supply chain partners into modular sections. Workers come through labour supply companies registered with Constructionline, with an emphasis on local resourcing.

“If we have a site in Swansea, for example, we will go to a local labour supply company and recruit six electricians to work that site for four years,” says Allso. Project management is also supplied externally, by Hertfordshire-based CLPM.

The work itself is done almost entirely inside the factories. “We use BIM, and design tolerances are accurate to 2mm, so there is minimal cutting at the sites,” says Allso. “There are very little wet trades, apart from things like fitting brick slips to the facades.

“It takes around 150 workers to deliver one complete house per day.”

The houses are typically two storeys and have a 9m by 5m footprint, though Allso says LCC is capable of building to a 17m by 10m footprint. The largest to date is a 720 sq m house on three floors.

Allso says his SIPs system could go up to six storeys. “Any higher requires a transfer plate and steel frame,” he says. “But we do not generally believe in high-rise living. We want to create family homes.”

As LCC’s name suggests, it has a strong sustainability focus. “Our homes have solar panels which effectively makes them zero carbon,” he says. “But EPC ratings do not include solar, so they currently achieve EPC grade B.

“The running costs of the homes are very low, in line with our affordability focus. These are the most efficient built by any national housebuilder, and we would like to force standards upwards.”

Unsurprisingly, he is scathing about housebuilding policy: “Government wants more affordable homes, but doesn’t deliver it. Major housebuilders are trying to build the least number of homes possible. Right to buy has destroyed affordable housing for councils.”

LCC is not a registered social land-lord because, Allso says, “we don’t want to be subject to Right to Buy”. He adds: “We have discussed with housing associations the option of buying up to 10% on a site, but no more. The buyers will be mostly private, and we have a separate group company, LCC Finance, which offers mortgage assistance.”

Interestingly, Allso plans to “protect” the affordable status of the homes: “The owners will not be allowed to own any other home and, even though freehold, the covenant on the property will restrict the resale value of the house to no more than the original price plus inflation.”

It sounds pioneering, which is exactly how Allso sees his company. However, he declines to comment on LCC’s costs or its margin. The firm has 6,900 individual plots across 12 sites, either “under option” or with “heads of terms”, and by the end of 2018 aims to have 30,000 plots awaiting or with planning permission. It forecasts delivering 10,000 homes a year from 2019/20.

Fixed factories restrict volume house-building. Instead, we have localised factories on site. It is a scalable model, so we could have 1,000 sites and 1,000 factories.– Simon Allso