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I-Team: Materials In Dorchester Fire Burn Faster, Prone to Collapse

BOSTON (CBS) - The massive fire at the Treadmark building in the Ashmont section of Dorchester is raising questions about a commonly-used building material.

Construction was nearing completion on the mixed-use condominium and affordable housing project when flames broke out Wednesday afternoon, causing millions of dollars in damage.

While the official cause of the fire will have to wait until the investigation is complete, the Boston Fire Department told reporters lightweight construction materials made fighting the fire difficult because they burn more quickly.

Dorchester Fire
Boston Firefighters battle large blaze on Dorchester Ave. (WBZ-TV)

"The dimension of the lumber is different," BFD Commissioner Joseph Finn said. "Think about if you are lighting a fire in a fireplace, the smaller stuff starts first, the larger stuff takes time to burn."

Finn was talking about engineered I-beams. Builders love them because they are strong and less expensive than solid wood.

However, the speed at which they burn has become an ongoing issue for firefighters.

Back in 2015, with the help of the Fire Chief's Association in New Hampshire, the I-Team observed an unscientific experiment to show the differences in the burn rates.

Dorchester fire
Treadmark building damaged by fire in Dorchester (WBZ-TV)

Firefighters set up an I-beam next to a solid beam and set them on fire.

Within minutes, the I-beam was significantly compromised while the solid piece remained stable.  After ten minutes, the I-beam burned through and started to sag under the weight of a cinderblock sitting on top.

"That floor would have collapsed by now, had there been a human being on that floor," explained NH State Fire Marshal William Degnan.

The construction material has been a contributing factor in several other massive fires around the country.

In North Carolina earlier this year, an apartment complex under construction went up in flames.  And in 2015, an occupied apartment complex in New Jersey also suffered extensive fire damage.

Despite these instances, the cheaper materials are allowed under Massachusetts and international building codes. However, they can't be used in buildings over six stories.

Watch: I-Beam Fire Demonstration

Builders are also using these beams in home construction, which can pose a danger for firefighters.

Several Agawam firefighters got out of one burning home just in the nick of time under a sagging floor.

"Probably one of the closest calls that we have ever encountered," Chief Alan Sirois told the I-Team in 2015. "The potential for loss of life was very high."

Code regulations in Massachusetts now require I-beams to be covered in sheet rock to increase the burn rate and give firefighters more time.

Finn told reporters the beams in the Dorchester Avenue fire were covered, but still remarked at how quickly the flames spread.

"Within nine minutes of our first arriving companies, the roof started to sag and cave in," he said.

Finn did say buildings like this are safe as long as sprinklers and other fire protection systems are in working order.  Investigators are trying to determine whether the sprinklers in the Treadmark building were turned off or didn't function properly.

Ryan Kath can be reached at You can follow him on Twitter or connect on Facebook.

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