The trussed rafter industry has Carroll Sanford of Pompano Bridge, Florida to thank for the invention of the nailplate. Back in 1952, Mr Sanford experimented with plywood gusset plates and varying combinations of glue, staples, nails and screws – eventually coming up with a light gauge steel connector plate.

This was taken a stage further by Cal Juriet who, in 1956, produced a version integrating teeth punched into the steel using a punch press.

Like many simple inventions, it was a winner. For the first time, timbers could be joined quickly and easily in the same plane – and the idea marked the beginning of the trussed rafter industry as we know it today.

Trussed rafters jointed by nailplates made their debut in the UK in the early 1960s; since then the nailplate has changed the way both domestic and commercial properties are designed and constructed.

The engineered punched metal plate fastener has meant that roof trusses can be produced using smaller timber sections and at lower costs than traditional alternatives.

But while the nailplate may have changed very little in the years since its inception, the industry has changed dramatically. All four system owners in the UK – Alpine Automation, Gang-Nail Systems Ltd, MiTek Industries Ltd and Wolf Systems – now develop sophisticated computer design software for their licensed truss manufacturers at home and abroad, ensuring their roof trusses comply with current legislation and to specify the correct size and location of each nailplate on each timber joint.

And these system ‘holder companies’ have helped push design boundaries ever further.

Roy Troman, sales and marketing director at MiTek Timber Structures Consultancy, said: “It is crucial to the trussed rafter industry that the tools required to increase the efficiency of both the design and manufacture of trussed rafters are continually developed and refined. Today, pretty much anything can be designed with the software, but not all equipment is capable of producing it easily, safely and efficiently.

“As always, the lowest cost producer of any truss that can be designed and transported will be the winner. The latest developments in trussed rafter manufacturing and handling equipment will allow manufacturers to reduce costs dramatically.”

MiTek has developed automated pressing equipment capable of producing more than 500 non-attic trusses from a single jig in an eight-hour shift, with average batch sizes of seven. Couple this with readily available networked saws, said Mr Troman, and the end result is obvious. Equipment capable of producing large, heavy structures easily and safely has also been developed to cater for the growth in large attic frames.

Mr Troman said: “It is no longer fantasy to envisage that robots similar to those used in the automotive industry will assemble trusses in the near future.”

In some respects the domestic roof truss market could be seen to be shrinking as the houses built are getting smaller and apartment blocks are becoming more common. However, the volume of housing being built has grown and timber roof trusses are being used on a growing number of commercial properties.

Mike Beale, managing director of Hampshire-based Gang-Nail Systems Ltd, explained: “The government says there must be 15 houses to an acre where there used to be 10, so the footprint is getting smaller, and 50% of those built have room in the roof trusses.

Flats on the rise

“The other thing that affects us greatly is the building of flats or apartments. That used to account for in the region of 15% of domestic construction but now, according to the NHBC, stands at 38% so this means one roof covering, say, eight dwellings, rather than eight roofs over eight dwellings.”

Also, builders are using attics to create floor space, so there is less business available to roof truss fabricators.

“However, 95% of roof truss manufacturers would tell you they are very busy for the time of year,” said Mr Beale. “Unless interest rates go through the roof, which is very unlikely in the next 12 months, I don’t think there will be any fewer roofs requiring roof trusses than at the current time, despite the dent in the market.”

Wolf Systems is heavily involved in developing software, particularly for room in the roof designs.

Sales and marketing director Alan Ritchie said: “We have expanded the software team who are generally doing more complex roofs which can be handled more easily and dealt with more quickly on site.

“We are always looking to do more detailed final drawings for builders to use on site.

“We are also developing management software which helps control quotations, scheduling and production. Manufacturers are looking for more of that to help them organise their business.”

Another issue at Wolf Systems is training. “Manufacturers are recruiting more and more people, and we run regular training courses twice a month – a one-day course which specialises in particular topics of software and roof design and a two-day course aimed at introductory or intermediate levels,” said Mr Ritchie. “Up to six people can be trained at a time at our own facilities in Coventry and they come from England, Scotland, Ireland and Wales.

“We always keep the software as easy to use as possible and we are providing the training service as there are so many new recruits to the industry. The training gives them the basics to take back to their companies where they can put it into practice.

“We have seen considerable investment in new manufacturing equipment in the past 12 months which has given our customers better quality trusses, made more quickly.

“On the design side, every roof is different so you never stop designing. We have to keep up with the architects who are always pushing the boundaries.”

Mr Ritchie said Wolf Systems is looking at the whole building model now rather than just the roof. “The roof has to fit into walls, as do the floors. More people are looking at the whole house supply so they can simplify problems and mistakes – and we have also looked at linking into standard industry packages such as AutoCAD.”

Another area the company is examining is electronic data exchange. “We want to be able to send information out in a format that other people can read which, in turn, saves paper and is therefore environmentally friendly.”

Unsung hero

Alpine Automation managing director Patrick Martin described the nailplated timber roof truss as the “unsung hero” of the housebuilding industry. “Its development has allowed the roofscapes of houses to become more complex,” he said, “and this progress has been due almost entirely to the development of powerful design software which visualises complex roofscapes and then automatically produces truss layouts, designs and manufacturing details.

“Over the next few years this software, combined with the internet, will enable roof information to be communicated between designer, fabricator and builder as two-dimensional plans or virtual reality views to facilitate the design and construction process. The roof information will also be combined with the design of other elements of the construction project to ensure the integrity of the entire structure.”

Mr Martin believes the versatility of trussed rafters has not been fully used by building designers. “A look inside houses in Florida or California will illustrate the potential of the roof truss for providing interesting ceiling shapes. I see this versatility being exploited as developers seek to add ‘something else interesting’ to their house designs.”

He said the true potential of trussed rafters for commercial roofs has also yet to be realised, and added: “The British Standards for trussed rafters have tended to limit spans but code changes prompted by the Trussed Rafter Association will increasingly release these restrictions.”