New homes are stronger, better designed and more energy efficient, but firefighters are sounding the alarm over engineered truss roofing and floors that burn faster than traditional construction.

Truss-style roofing has been around since the building boom that followed the Second World War, but engineered materials are increasingly using smaller and smaller dimensions of wood, leading to faster-spreading fires.

Images of the Campus Court Plaza in Waterloo engulfed in flames in April 2010 remain burned into the memories of many, with smoke visible from kilometres away.

Flames shot from the roof after the fire got into the structure of the building, spreading from one section of the plaza to the whole complex in minutes.

Larry Brassard, deputy fire chief with the Waterloo Fire Department, battled the Campus Court fire and says "A fire will double in size every minute."

It took only two hours to completely blacken the 30,000 sq. ft. structure, and Brassard says the primary reason is spread so fast is the way the plaza was built, with a lightweight, engineered truss roof.

"Lightweight construction is used in hundreds and hundreds, thousands of buildings across Ontario and Canada, but it does present risks when it becones involved in fire."

Advances in technology allow truss manufacturers to use less wood during fabrication and still create a stronger, more durable and more affordable product. And increasingly, that means traditional 2" by 6" lumber is replaced with a higher grade, stronger, 2" by 4" stress-tested wood.

"The dimension of the wood used in the building products has gone down considerably and so the burn time between the start of a fire and when collapse occurs during a fire situation is much less today," Brassard says.

Burn tests conducted in the U.S. compared truss roofs with a traditional ‘stick roof.' While the truss roof collapsed in five minutes, under the same conditions the stick roof is still standing after 21 minutes, collapsing only after the wood has turned to ash.

Brassard says these new roofs mean firefighters now have to judge whether to risk their lives, "If the fire involves the structure at all, if it gets into the wooden structure, the officer has to make an assessment about sending those people in. So he has to decide whether it's worth a firefighter's life to go in and save property."

Coming up in part two: Why build with truss roofing and floors at all? Manufacturers and home builders say the demand for open concept living is to blame.