My initial column in the June 2010 issue began a discussion about buildings called "mixed multiple occupancies," or "taxpayers," as they are known in some places. We noted that they have plenty of internal void spaces, which means a fire can travel quickly beyond its room or area of origin. With...
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My initial column in the June 2010 issue began a discussion about buildings called "mixed multiple occupancies," or "taxpayers," as they are known in some places. We noted that they have plenty of internal void spaces, which means a fire can travel quickly beyond its room or area of origin. With that in mind, the potential is great for a tough firefight and an extreme life-safety problem when the building is occupied. Basic engine and truck work is the order of the day. Fire departments confronted with a working fire in a mixed multiple occupancy must perform their duties in a methodical manner with coordination and communication.
• Construction — Most of these structures were built of Type V wood-frame construction methods in the late 1800s or early 1900s. Everything used to build them is made of wood or other combustible materials. This also means there will be balloon framing in place — expect plenty of void spaces for fire to travel in. Exterior walls for wood-frame buildings may be covered with wood, aluminum or vinyl siding or even old asphalt shingles.
Many other mixed multiple structures were built using Type III "brick-and-joist" methods. This means the outer walls are of masonry construction. Floor joists that support each floor rest on an exterior wall shelf while the other end of the joist spans the distance to the other side of the building. In wider buildings, floor joists span from the exterior walls inward to a girder supported by a column or a bearing wall in the middle of the structure. A joist from the opposite exterior wall spans inward the same way. The joist ends meet at a common support beam, hence the term "brick-and-joist" construction. (Note: In many Type III buildings, the joist ends have been built into the outer walls creating a joist "pocket." This condition creates a very unstable wall if there is any movement in a joist or where a joist may rotate or give way, as the other end of the joist moving will destroy the masonry wall at the connection area and cause collapse. Also, this type of construction creates both vertical and horizontal void spaces like balloon-framing.)
• Apartment layouts — Usually, access to an apartment is through an ordinary entry door from a common hallway. The apartment areas generally have room enough for a small family; however, there is no guarantee about how many people may be living in one unit!
Once inside an apartment, a single unit can have a kitchen-dining area, a single full bath, two bedrooms and a living room. As you pass through the kitchen-dining area, the bathroom and bedrooms will be to the other side of the suite. There will likely be a living room at the end of the rooms. There may also be a narrow hallway that separates the living room from the bedrooms. In heavy smoke, this will create a maze-like problem for firefighters trying to conduct a search operation. There may be only one suite or as many as four units per floor.
In general, there can be several different floor layouts. There may even be a front entry door at street level leading up to an apartment over the store. In any case, firefighters should expect a confusing situation in heavy smoke and heat conditions.
• Inside the mixed multiple — Interior walls will be plaster over wooden lath strips. In many buildings, remodeling has seen sheetrock or drywall placed over old walls, but in some cases, the old plaster and lath has been removed and replaced with drywall. Some remodeling has seen new walls covering over the old walls, creating double wall cavities. (A note of caution: In some remodeled structures, polycarbonate-coated drywall has been used to prevent wall damage. This is a problem for forcible entry because of its resistance to damage. This can create an operating hazard to firefighters who may have to perform a survival move such as opening a wall to get through to a safe area. Firefighters using forcible entry tools during drills have found this wall nearly impossible to break through, a situation made much worse under a stressful fire condition.)