Fire Exposes Weaknesses Of Architectural Design

Fire Exposes Weaknesses Of Architectural Design

Concealed spaces and combustible material are provided by esthetic roof design.

Photos by Richard A. Coleman

A two-alarm fire in a recently built shopping complex in Stockton, Calif., pointed out some important building construction trends that seem to be apparent in much new construction. The most disturbing trend is the extensive use of combustible materials for architectural design and construction of large structures.

At this fire, we found decorative wood siding from foundation to top plate. There were wood-covered eaves with attic venting around the perimeter of a 4000-square-foot truss-type, wood shingle roof. The truss wood construction consisted of 2X4 wood trusses fastened with metal cleat truss plates. Several articles have been published warning fire fighters of the danger of early roof collapse with this type of truss assembly.

Access partially blocked

The six different shops housed in this complex were located off the main thoroughfares. Customers had to go through narrow drives to reach the front parking areas. Two sides were completely blocked off from fire or vehicle access. This required the hand-carrying of all hose lines for fire and exposure protection on the blind side.

When the fire was first reported just after noon last Dec. 29, Battalion 2 responded with Engine 10, Engine 4, Truck 4, and Medic 4. En route, Battalion Chief James Raines reported smoke in the air. At the scene, he found smoke coming from the entire roof area and requested the second alarm. This dispatched Engines 6 and 11, Truck 2, Medic 2 and Battalion 1.

The electrical utility company was notified for curtailment of electrical service. To increase available fire flow, the water utility was asked to divert water in the fire mains to the shopping plaza.

Engine 10 was positioned in the parking area near the portion of the building with visible burning. The crew attacked the fire with preconnected 1½-inch lines. The main body of fire appeared to be involving the exterior wood siding, eaves, and portions of the roof. Flames extended horizontally in both directions following the overhead eave construction.

Fire spreads to attic

When the initial knockdown of visible flame was accomplished, it could be seen that fire had penetrated the attic and was extending throughout the entire 4000-square-foot area.

Metal truss plate, arrow, used to hold truss members together contributes to danger of early collapse of wood truss roofs.

The initial attack line was then repositioned in the attic area, and the other preconnected line was positioned at the west end of the structure. A set of lead-in lines was placed to cover the attic at the breezeway, and still other lines were taken aloft for full roof and exposure protection. All the lines were in position and in operation before the roof was vented.

It turned out to be a good setup and attack, considering the attic area roof construction. An indirect fire attack worked well to control and extinguish the fire in all quadrants of the attic. Ventilation helped remove smoke and heat.

Trusses were weakened

When visibility had improved, the amount of direct fire damage to the attic area was very visible. Truss plate integrity was viewed to be very weak where there was direct flame impingement. In most areas of heavy charring the truss plate had literally fallen off the truss assembly and was lying in the attic space completely intact. Any lateral movement of the roof assembly would have certainly caused truss failure and possible roof collapse. All fire suppression personnel should be aware of this type of hazardous construction practice.

It was determined that the fire had started in a small alcove area in the rear exterior of the gift shop in a discarded cardboard box of Christmas decorations. The fire is under investigation at this time.

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