Commercial Construction Considerations: Interior Features

In last month's article we looked at the building process and the building floor plan. This month we will discuss walls, doors, ceilings, flooring, and roofing.

In addition to the floor plan, the architectural portion of a building design will include wall and door types. Buildings are limited to certain fire areas; the International Building code defines a fire area as "The aggregate floor area enclosed and bounded by fire walls, fire barriers, exterior walls or fire-resistance rated horizontal assemblies of a building." The fire area is a compartment within a building that is intended to prevent the spread of fire to outside the fire area. The fire area is determined by the occupancy of the facility and whether or not it has a sprinkler system.

There are literally hundreds of different assemblies that create the fire walls, fire barriers, exterior walls or fire-resistance rated horizontal and vertical assemblies. It is important to know what fire areas exist and how they are separated from other parts of the building.

These assemblies can range from multiple layers of gypsum board with metal studs 16 inches on center to concrete block walls. It is vital to have an idea of what may exist and how you would deal with it. The location of fire areas is very important when considering vertical ventilation; if you ventilate in the wrong location you may not be providing any ventilation of the area under fire conditions.

Door Styles
Forcible entry is something we spend many hours training on, therefore knowing the types of doors that exist is very important to firefighting operations. The door assemblies, door material and construction that exist need to be known. In addition to the door construction, it is important to know what types of locking systems are in place. Knowledge of the doors and what the door frame assemblies could possibly be constructed of and the type or access control systems that may exist are also important.

Many facilities have moved away from the typical lock and key door access systems and have gone with biometrics, proximity readers, or card access systems. Doors that use these types of access control typically make use of either a magnetic lock or electric door strikes. Often there is no way to tell the difference between these and standard lock types. There is a big difference when trying to force a door with a magnetic lock compared to a traditional lock. It is also import to know of any specialty type doors that may exist, including roll-up doors, and revolving doors, and how you will deal with these obstacles when you see them.

Ceiling Types
Another important construction feature that is architectural in nature is the ceiling type. This feature will have a large impact on fire behavior and on the behavior of the structure supporting the roof or the floor above. There are generally three ceiling types:

  1. a hung lay-in type ceiling, that is one with a hanging two-by-four-foot or two-by-two-foot grid with ceiling tiles laying in the grid,
  2. a hard ceiling system, i.e. gypsum board attached to either the bottom of the structure above or a frame of some type, and
  3. no ceiling, where the occupied space is open to the structure above.

The option of no ceiling is becoming far more popular due to cost savings and the addition of volume to a space; however this type of construction leaves the building structure, including lightweight steel bar joists and engineered lumber, unprotected, which could lead to structural failure in a short period of time under normal fire conditions.

Floor Systems
The flooring system is a construction feature that I feel is important to mention. I know many of you are probably thinking, well the floor is the floor, supported by some type of structure that will be discussed later and the floor has some type of floor covering, carpet, tile, etc. Firefighters need to know that there are many types of flooring installed on top of the building structure and these include wood products such as plywood, OSB (oriented strand board), pre-cast concrete, and poured-in-place concrete.

In addition to the traditional flooring systems, as building occupants have changed to an open floor plan they have also started using raised floor systems in many of these facilities. A raised floor system is a floor above a floor. The floor system is actually comprised of a floor that is part of the building and a floor that sits on top of it. There are pedestals that hold up 24-by-24-inch sections of floor. Once these sections are removed, you have access to the under floor plenum, this space is used much like the plenum space that has traditionally been above ceilings.

While you will not find many combustible products in these areas, the raised floor system creates a way for the products of combustion to be distributed throughout the building. In the heating, ventilation and air conditioning segment I will discuss how under floor air distribution works and some things firefighters should be on the look out for.

Roofing Materials
The final item I wanted to discuss is roofing systems. Performing vertical ventilation is something we normally do without thinking; however, as we all know it can be difficult and dangerous. Firefighters need to have a basic understanding of commercial roofs and issues that can exist. There are hundreds of roofing products out there today, ranging from foam, to thylene propylene diene monomer (EPDM), and bituminous products.

Do to recent trends in energy savings most of the new roofs and many retrofitted roofs will have insulation on them. Most roofs are built in a system and start with a basic roof deck. The roof deck can be anything from metal, to pre-cast concrete, to gypsum board. On top of the deck can range from insulation to the first layer of roofing material to concrete. On top of that will be additional insulation which will typically be the "board type" then several layers of roofing material and then a cap sheet.

It is important to know what types of roof structures you have in your response area so you know how to approach them. Metal roofs are becoming more popular and are often installed over existing roofs, which is something that you should keep in mind when you see one.

Fire departments should try to develop a working relationship with the facility managers of large commercial facilities in their response area. You should find out who is in charge of upgrades and renovations and work with them to have updated plans in the fire department files. Then pre-plan these facilities so there are no surprises when you pull up.

I believe that the ceiling construction, door and access systems, the flooring, and roofing systems are major components that affect firefighting. Next month we will discuss concrete, how it is used in the building process, how it reacts to fire, and some of the locations you may find it.


MATTHEW STIENE, a Firehouse.com Contributing Editor, is a project manger for the Mecklenburg County Real Estate Services Department, and a firefighter with Robinson Volunteer Fire and Rescue, in Charlotte, NC. He is a licensed professional engineer in North Carolina, New York and Pennsylvania, and is a certified facility management professional. To read Matthew's complete biography and his archived articles, click here. You can reach Matthew by e-mail at mattstiene@hotmail.com.

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