Big Box retail facilities have been a growing part of the retail environment for the last 15 years. These types of facilities have created some unique fire protection challenges.
In order to discuss the differences associated with big box retail from that of more traditional retail occupancies, one must distinguish big box retail from other retail occupancies.
Typical big box retail spaces have ceiling or roof heights in excess of 5 meters (16 ft) and in many cases as high as 10 m to 12 m (35 ft to 40 ft). This permits the storage or display of merchandise to occur above the 3.7 m (12 ft) height, and in many facilities above a 7.6 m 9.1 m (25 ft to 30 ft) height. These types of retail stores will typically display products at lower elevations 1.8 m to 2.4 m (6 ft to 8 ft) above the floor, and store goods above these displayed products.
Big box retail facilities typically have large footprints, many of which approach or exceed 9,000 m2 (100,000 sq ft) in area. A variety of commodities is displayed and stored within these facilities and includes items such as soft goods/ clothes; bedding materials, including mattresses and pillows; furnishings of all types; paints; home repair and building materials; household cleaning chemicals; lawn care chemicals; and plastic commodities, such as toys, lawn chairs, furniture, etc.
The variety of commodities stored and displayed creates special challenges to protect the occupants and the commodities, while some of the design characteristics of the building shell often provide features that achieve a degree of "built-in safety." Some of the building design features that provide an enhanced level of fire safety for this type of retail environment include the following:
The high roofs/ceilings, in conjunction with large footprint areas, create a very large volume of space that allows for tenability to be maintained during a fire condition for an extended period of time. This gives occupants more time to move away from the fire condition and evacuate the facility. This is due to the time it takes for the smoke and combustion gases to descend from the roof/ceiling to a level of 1.8 m to 3 m (6 ft to 10 ft) above the floor, which would then create an environment where evacuating the area becomes difficult.
All of the U.S. national building codes currently contain (and have for many years) requirements for automatic sprinklers to be installed in retail occupancies above the threshold limits of around 1,100 m2 to 3,700 m2 (12,000 sq ft to 15,000 sq ft). Additionally, since the big box stores often contain high-piled storage, sprinkler protection is required per the High-Piled Combustible Storage provisions per the U.S. fire codes. The sprinkler requirements of high-piled storage are more stringent than normal retail, require a much greater water density for the sprinkler system, and more overall water at the site for fire department operations. Essentially, the fire protection is more similar to a large warehouse than a retail store.
Many of these stores use Early Suppression Fast Response (ESFR) sprinklers. These systems are designed to extinguish a fire condition by responding to a fire condition earlier in its fire growth with water densities that can extinguish the fire. This is an enhancement compared to conventional sprinklers that are designed to control and contain a fire condition.
The automatic sprinkler system protection designed for the variety of commodities in these displays and storage configurations has an excellent record of containing developing fire conditions for the time necessary for evacuation to occur and the fire department personnel to arrive and provide necessary support for the extinguishing systems.
The water requirement for some of these big box stores can be up to four times greater than a typical retail store. It is not uncommon for a fire pump to be installed in order to meet these requirements. Occasionally, a water storage tank is required when the municipal water supply is not sufficient to provide the necessary water for fire flow requirements.
These types of buildings are normally of one-story design, allowing most or all of the exits to be at or near the exterior grade around the building. This facilitates both the evacuation procedure as well as the fire department response operations.
However, there are some characteristics of the building designs used for many of these big box retail facilities that should be noted and addressed. Most of these focus on means of egress concepts.
It is not unusual for designs to have two-thirds (67%) of the means of egress provided through the main entry wall of the building. Several factors should be considered regarding this design.
Of these main entrances/exits, one is typically used as the store entry and, as such, maintains reasonable clearness for not only the ingress into the store but also egress out of the store. However, other front-of-store exits are typically designed to accommodate customers leaving the store after they go through checkout lanes. One consideration regarding this concept is the checkout lane areas, which are typically designed with dimensions to allow for necessary egress through these areas. However, shopping carts that are used by the customers to accumulate and transport the goods they want to purchase are sometimes not considered. These, if left in the exit path, may result in the available exit width being substantially reduced. For example, if the big box retail store is a home improvement type of facility, the shopping carts may be a variety of sizes, some of which are capable of carrying 1,200 mm x 2,400 mm (4 ft x 8 ft) sheets of plywood, insulation board, or other large types of materials. Therefore, if these carts are in line at the checkout registers and the carts are abandoned in place during an emergency condition requiring evacuation, adequate exit width may not be available to accommodate the number of occupants these exits were designed to serve. The interior design should address the exit width requirement by considering the following factors:
- the location of product displays, (in many projects, the vestibules at the main entries/exits are being used to display merchandise) adequate exit widths must still be provided around these display areas;
- space should be available to store carts out of the required exit paths when customers leave the carts and carry their purchased goods out of the store in bags; and,
- space for the required exit widths must be maintained even if some carts are abandoned at the checkout lanes.
To provide an example of the main entry/exit concept, consider a 9,000 m2 (100,000 sq ft) retail facility.
The code-calculated occupant load would be approximately 3,334 people. If two-thirds of the exits were located in the customer entrance wall, this would result in 2,234 people needing to exit via the front exits. This would represent approximately 8.5 m - 11 m (28 ft to 37 ft) of clear exit width being required, depending on the adopted code.
Having such a high percentage of exiting occurring through the main entry wall means that the number of exits available on the other exterior walls of the facility might only provide one-third (33%) of the total exiting of the building. Some of these other exits are often only accessible through back-of-house areas that could involve shipping/receiving areas, stock areas, or other back-of-house support areas. It is also common for some of the egress path for occupants of select facilities to be through garden centers. These can require occupants to travel through fenced-in areas, some of which are partially roofed areas and areas that are significantly merchandised.
These are again important considerations when designing exits to assure these exit paths will remain available given the operational need of the store to move and stock goods.
The entire concept of having such a major amount of main egress at the front wall through which occupants enter was primarily developed for retail projects before big box retail existed. This was when much of the merchandising was on display counters and racks that varied in height from approximately 1 m to 2.4 m(3 ft to 8 ft). This allowed for the occupants to see over some of the fixtures and merchandise which allowed for a much clearer view of the entire facility, and occupants could easily identify the wall that they entered through. Thus, it was felt that these occupants would be most familiar in finding their way back to the main entry. As the commodities, merchandise, and storage have grown to such heights that occupants cannot see any of the exterior walls from many areas of the building, it is easy for occupants to lose their bearings and not be able to identify quickly the wall of the building through which they entered. Given the consideration discussed, it would appear that a more balanced exit system would provide a greater level of protection for store occupants.
As the heights of the displayed and stored goods increase, the location and visibility of exit signs are increasingly important to identify the path to exits that are not visible to the occupants from many areas of the sale floor. Therefore, the number of exit signs necessary must be based on the configuration of the fixtures as well as the fixed partitions in the facility. Also, the height of these signs above the floor must be viewable by the occupants without searching and at heights and locations that are not obscured by other signage or decorations.
Fire alarm systems that include occupant notification have not been required for these big box retail facilities by most of the U.S. codes written before 2000. However, this is now changing since occupant notification systems are now being required per the International Building Codes for retail occupancies with an occupant load of 500 people or more. The question is whether occupants actually respond to these occupant notification devices if the occupants are not in the immediate area of the developing condition and therefore do not sense smoke and do not see the fire condition. After all, in the past, the two most widely used national codes did not require fire alarm systems with occupant notification capabilities within large retail facilities, and no documentation related to fire and life safety experience has been submitted to indicate a need for these type of systems in such retail occupancies. These types of facilities may be better served by having public address systems in combination with staff trained to make voice announcements and aid people to evacuate. This also allows for the announcement to the occupants to provide for special instruction regarding evacuation needs or methods.
Ed Schultz is with Code Consultants, Inc.