Highly engineered truss roofing and flooring allows builders to fulfill the demand for open concept living, but from a fire safety perspective the practice isn't ideal.

While home builders and manufacturers are enthusiastic about the new, lightweight materials being used, many are unaware of how they react in the case of a fire.

In engineered trusses, dozens of pieces of wood, attached with metal fasteners, mesh together seamlessly thanks to laser accuracy.

Dan Jackson, owner of DJ Jackson Engineered Truss Components, says there is a huge manufacturing advantage.

"[You] maximize the potential of the wood, thus, less amount of wood is needed to build a 30 foot truss using a two by four versus two by six bottom bottom chords."

A chord is the technical term for the horizontal pieces of wood that join the roof trusses together.

The triangular shape of the roof construction makes it strong, but it also means that all the parts, both the angled roof and horizontal chords, carry the weight equally.

Machine-tested lumber means trusses are getting even stronger. Jackson says "There's a value stamped on the wood. It could be 1650, 1950, 2100 pounds, and that piece of wood is designed to carry that load per lineal foot."

Those numbers take the engineering out of the hands of builders, with every piece having a place and purpose.

John Meinen is a builder with Pinnacle Quality Homes, he says "It comes in an engineered, one-piece truss, which is the floor, the roof, the side walls and everything up there."

The new technology allows Meinen to build custom homes that have 30 feet of open floor space, which isn't possible with a conventional stick roof.

"With stick framing you can only go so far without a bearing point, without a beam or without whatever. A truss enables you to go 50, 60 feet of wide-open area."

While that seems to be the style homebuyers prefer, firefighters say there's a danger that comes with those trusses.

Fire officials say a truss roof can collapse in less than six minutes once exposed to fire, something not all manufacturers and builders know.

Jackson thought the additional pieces in the webbing of a truss would perform better than a traditional stick roof.

"The chords, meaning a top and bottom chord, are larger, but there's not webs to it. So once a bottom chord or top chord is burned through then there's really nothing holding your roof together."

But Sean Tracey, regional director of the National Fire Protection Association, says there's a good reason truss manufacturers don't know about how their product fares in a fire.

"The reality is that none of these truss designs are actually tested for their fire performance and there's no requirements under building codes for how they perform in a fire."

And that's a scary thought both for homeowners and the fire crews on the front line who are concerned about the safety of residents and firefighters.

Coming up in part three: What the Ontario Building Code has to say and why some critics say nothing will change until after more firefighters lose their lives.