Summary

  • SIRS comprises SIPs, trusses and cassette floors.
  • Uptake of the system has increased since NHBC approval.
  • Persimmon Homes and Opal Homes have used the system.

Michael Donaldson, product development manager for Donaldson Timber Engineering’s Structural Insulated Roofing System (SIRS), wasn’t immediately recognisable when he came in. Perhaps it was something to do with the T-shirt, the dusty jeans and the site boots? “We’re really busy” he explained “and I like to get involved hands on in the manufacturing process.”

SIRS incorporates SIPS panels (rigid insulation sandwiched between two layers of OSB); roof trusses; and cassette floors (it excludes purlins). It was developed with the help of Kingspan and has TRADA and NHBC approval and incorporates BBA components and PEFC timber.

“SIRS is aimed at the volume market ideally, where manufacturing can respond to the same type of design in numbers,” Mr Donaldson explained. “And while it is not a niche market product, its post-build green credentials respond well to the social housing market and to the drive for super-insulated homes which the Code for Sustainable Homes is producing.”

He admitted the system was more expensive in terms of materials than standard roof trusses but said savings could be found in ease and speed of erection. “And on the issue of market share, I anticipate that SIRS will take only a tiny percentage of our traditional roof truss market. People who are buying SIRS are looking for something different.”

Managing director George Watson was the brainchild for the system in 2003 when he saw a market opportunity for an alternative roofing system, as the growth in flatted developments led to a shrinkage in the traditional truss rafter market. Alternative products already existed, such as SIPS, I-joist roofs and off-site systems, but Mr Watson believed there was still a gap for a solution designed to make building of attic roofs easier, allowing for more floor space and longer spans, and which would also respond to issues of sustainability and site safety.

The design of the SIRS system is predicated on George Watson’s idea of “making things easier” for the builder and the general system development was undertaken by TRADA.

Launched at Interbuild in 2006, SIRS was specifically aimed at the housebuilder market, both private and social housing sectors. It is seen as an obvious development of DTE’s current market offering.

Interest in the system was widespread, but uptake was limited until NHBC approval was gained earlier this year.

One big player who batted early for SIRS was Persimmon Homes, who trialled the system successfully at its site at Irlam in Manchester, along with four other prefabricated roofing systems.

Currently order books are building for SIRS, with orders from Opal Homes for its site in Anstruther in Fife, where SIRS complements Opal’s thin joint system of build. Lomond Homes is trialling the system on a garage roof which was too wide for other systems; and the Westbury Partnership, found its “room in the roof” design for a Coventry site was ideal for SIRS.

SIRS has also raised interest in the self-build market, following a presence at the Home Building and Renovating show in Glasgow in May, following which they have quoted for some 20 roofs.

The system claims to offer several advantages – a reduction in erection time by up to 60-80%; 25% more floor space; and suiting a variety of roof shapes. The inclusion of sustainably sourced timber and insulated panel construction means SIRS is also being marketed as a potential contributor to low carbon build.