Chris Duckworth of SIP Build UK discusses the slowly rising trends of using SIPs and off-site construction, and ponders why it’s taking the industry so long to adopt this effective method.
It’s not that long ago that the recession left both good and bad housebuilders obliterated. The bad were the first to go, but even some of the very good were left casualties. The industry fell into a state of confusion and panic, coupled with an abundance of tradesmen who would chew off their own arm to secure a wage.
Fast forward four years and we find ourselves with an ever increasing need for homes, schools and healthcare buildings. Schools and healthcare places remain the responsibility of the Government, and as a result they have to carry on. Housing on the other hand has largely been left to private developers.
The improvement in the economy and the recovery of the housing sector has seen demand for the trades return, only to find that there is a large gap in the availability of skilled labour. This ever increasing rise in standards for thermal performance that building regulations demand has only exacerbated the need for skilled trades.
Three years ago, it would be inconceivable that a housebuilder would consider using SIPs to build their project. Phrases such as ‘cost- prohibitive’ and ‘over-performing’ were often used to describe the method. Fast forward to the increased standards of thermal performance and airtightness that Building Regulations now ask, and you have a situation that requires ever increasing wall thicknesses and secondary systems or far greater quality control to achieve the performance required.
Unlike traditional construction, SIPs are produced off-site and have an incredibly quick installation time. It is not inconceivable to erect a four-bedroom house in less than two weeks, which includes all external structural walls, all internal walls, as well as floor joists, floor decks and the roof structure.
With the need for space at an all-time high, a major benefit of using SIPs is the thinness of wall that can be achieved. A wall build up of only 230 mm using a rendered system to give a U-value of 0.20 W/m2K would be almost unthinkable with block work. The same U-value can be achieved for a brick outer skin build up with an overall thickness less than 300 mm.
SIPs are a dimensionally stable product that, unlike timber frame, move very little once built. This means that the usual snagging issues of a timber frame are removed. The off-site nature of the production allows for accurately constructed, high-quality buildings with known performance. The process is also less prone to weather disruption and ‘Friday afternoon’ quality issues. Knowing the costs before the project begins and having a programme that is unlikely to be affected by the weather means that the budgeting and programming of sites can start to become more accurate, with costly preliminaries reduced.
The use of one contractor pulling together a number of trades can help the management of the small to medium site, which in turns allows the developer’s management team to spend time on other areas. Major items such as doors and windows can all be procured in advance, safe in the knowledge that the off-site construction and accuracy onsite will allow sites to be secured faster, with the major benefit being that the internal works can progress at the same time as the external works. The removal of brickwork from the critical path during the winter period, or summer with the unreliable UK weather, is also a benefit to many.
For tight and contentious sites, the use of a SIP structure can reduce transport movement to the site, therefore the muck and debris that is strewn on the surrounding roads is limited due to a reduced number of deliveries. The system also produces less site waste, ultimately meaning less skips on site, which often proves to be a hidden cost.
In summary, the only thing that is currently holding developers back from using this system is the belief that because we have always done it that way, it must be right. This is the only industry that greets innovation and new products with disdain and caution beyond all reason.
SIPs have been around for decades now and the market appears to be waking up to the benefits and speed that the system brings. As with all great solutions, if enough people find out about it and start using it, SIPs will soon become the norm.
Chris Duckworth is managing director at SIP Build UK