Size – Up Considerations
Construction: Most often, these will be either Ordinary or Non/Limited Combustible, with common void spaces either above or below the occupancies, dependent on construction type. Based on the significant potential for lateral fire spread, it is wise to concentrate the suppression efforts on keeping the fire in the involved unit, with handlines placed to cut off any fire travel. If there is lateral spread in the overhead area, be sure to open up all vertical arteries to allow the heat out of the building prior to pulling the ceilings (photo 5). If the ceilings get pulled prior to roof ventilation, the potential for a backdraft coming into the first floor area is significant.
Accessibility to these occupancies may be difficult, as many of these units are fitted with roll-down gates, which can hide the location of the fire, and allow the fire to grow exponentially. Rear access will be well fortified with multiple locks, including some homegrown varieties. It would be wise for the occupants to participate in a Knox-Box access program, which can save time making access into the building.
Roof recon may find the presence of cornices, facades, and parapet walls. Cornices and facades can be mounted to the front of the storefront exterior wall, placing an eccentric load on the wall. Mostly decorative in nature, these spaces can also hide a serious fire spreading from floor to floor, from the space between the floors, into the façade, and out to the upper-floor windows (see Photo 6). There may also be a parapet wall, a free-standing, non-load bearing wall extending above the roof line. This is considered to be a free-standing wall, sitting above the roof line on a lintel over a large opening, such as a large display window. These lintels can be constructed of steel, or can be a Glulam header or a Microlam beam. Excessive heat from the fire can cause the lintel to warp and fail, causing the parapet and front wall to collapse (see Photo 7). A good tactic to keep an eye on this situation leaves one front window intact for every two windows that are vented. Since the structural support on the front of these buildings rest substantially in the lintel, any weakening or buckling will break out these remaining windows. This is a good indicator that the front wall is about to collapse.
There may also be the presence of a rain roof, a new roof built over an existing roof. This can be a cheaper option than ripping off the old roof, and can even be constructed of lightweight materials, such as TJI’s or engineered lumber. The addition of the rain roof adds a significant load upon an already weakened roof, and since the rain roof acts as a heat accumulation point, this will allow the original roof to burn away, leading to a catastrophic collapse under fire conditions.
Occupancy: Depending on the use, there can be a large amount of issues to deal with. Presence of hazardous materials and flammable gases in these units can significantly increase the fire load and accelerate fire spread. Utility service can be compounded by multiple occupants; back-up generators can be in place; and gas may enter the structure at higher pressures to feed multiple meters.
Another problem with these buildings is the transient tenants that occupy the spaces within. Businesses moving in and out frequently, or expanding into multiple spaces can give these buildings a very interesting layout. Walls can be added or deleted, depending on the needs of the tenant. One of these occupancies in my response area has 12 units identified in the building, but walls were removed between three of them to facilitate the needs of the company. However, without proactive pre-planning, we would not have known it if we had an emergency there prior to the inspection.