Construction Concerns: Remodeling

Article and photos by Gregory Havel

When houses and other buildings are remodeled, modern manufactured construction materials are often used instead of the materials used in the original construction 50 or 100 years ago. In today’s marketplace, the manufactured materials are advertised as lighter, straighter, stronger, and less expensive than the materials used in the original construction. The advertising is true under ordinary conditions. Under extraordinary conditions, like a structure fire, the materials do not perform in the same way and do not have the same inherent fire resistance as the building’s original materials. When an older building has an addition or modification using modern manufactured materials, expect that part of the structure to burn faster and hotter and to collapse more quickly than the older part of the structure.

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Photo 1 shows the exposed joists in the basement of a house built in 1945 that is being remodeled. The joists on the left are the original structure, of 2 x 12 lumber measuring 1 5/8 x 11 5/8 inches. The two 2 x 12s nailed to the last lumber joist on the right measure 1 1/2 x 11 1/2 inches, the standard size since the 1960s. Rough-sawn (unplaned) dimensional lumber in older buildings will measure the full dimensions of the lumber size.

The joists running at right angles from the triple joist in the center of the photo are manufactured I-joists, installed to close a stairway opening that will no longer be used. The top and bottom members are laminated veneer lumber (LVL) and the web is oriented strand board (OSB). These I-joists are supported by galvanized sheet-metal joist hangers nailed into the lumber joists at each end of the stairway opening.

The left side of photo 1 also shows the underside of the one-inch-thick tongue-and-groove subfloor boards that were laid at a 45-degree angle to the joists and nailed down. The subfloor shown on the I-joists in the former stairway opening is ¾-inch-thick plywood. (OSB is often used in place of plywood.) The position of the joist hangers has been adjusted vertically so that the top surface of the plywood matches the top surface of the original one-inch subfloor boards.

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Photo 2 shows the top of the subfloor. At the top of the photo are the original ¾-inch-thick tongue-and-groove oak floorboards, nailed into the subfloor at right angles to the floor joists. The center of the photo shows the original one-inch-thick subfloor boards, exposed where a wall was removed. The lower part of the photo shows the new plywood subfloor, nailed into the I-joists below. Fiberboard floor underlay will be installed on top of the plywood subfloor to make the carpet and pad throughout this area smooth and seamless.

The materials and methods shown in these photos are common in the remodeling of and building additions to older buildings, including the replacement of floor joists and deck ordered by building inspectors after structure fires.

The finished product will be attractive and will completely conceal the former stairway opening. This is not a problem under “ordinary” conditions. However, if there is a fire in the lower level with the exposed floor joists, the floor over the former stairway will become a “man-trap”:

The ¾-inch plywood floor deck will be weakened by heat and will burn through more quickly than the combined 1 3/4 inches of solid lumber in the floor of the original construction.
The manufactured wood I-joists will weaken and burn through more quickly than the 1 5/8-inch solid lumber floor joists in the original construction.
The carpet and pad will provide insulation from the heat of the fire below, and a thermal imaging camera will show a surface temperature close to room ambient temperature, rather than the heated surface that would show if it were reading the hardwood floor.

If a remodeling job like this is done by a reputable contractor, there will be plans on paper and a building permit and the building inspector may even let us know about the project. If the job is done by a less reputable contractor, a handyman, or a homeowner with a “do-it-yourself” book or Web site, we are unlikely to find out about this new feature of the older building until it collapses under us while we are performing primary search or fire attack.

Since the 1960s until his death, Francis L. Brannigan told firefighters, “The building is your enemy. Know your enemy.” This statement is as true today as it was 45 years ago, especially considering today’s construction methods and materials and the reduced staffing of today’s fire service compared with past decades.

For additional information on the behavior of manufactured construction materials vs. traditional construction materials under fire conditions, visit:

Building Construction for the Fire Service, 4^th edition, by Francis L. Brannigan and Glenn P. Corbett. NFPA / Jones & Bartlett, 2008 (especially Chapter 6, “Wood Frame Construction”).
NFPA Fire Protection Handbook, especially the sections on fire behavior and construction types and materials.
The Underwriters Laboratories on-line short course titled “Structural Stability of Engineered Lumber in Fire Conditions,” at http://www.ul.com/fire/structural.html.

Gregory Havel is a member of the Burlington (WI) Fire Department; a retired deputy chief and training officer; and a 30-year veteran of the fire service. He is a Wisconsin-certified fire instructor II and fire officer II, an adjunct instructor in fire service programs at Gateway Technical College, and safety director for Scherrer Construction Co., Inc. Havel has a bachelor’s degree from St. Norbert College; has more than 30 years of experience in facilities management and building construction; and has presented classes at FDIC.

Subjects: Building construction for firefighters

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