In the last year or so, there have been several fire incidents during the construction of wood-framed residential buildings. Recently, in January 2021, a fire at the Ely at Fort Apache apartment complex in Las Vegas completely destroyed the building, racking up an estimated $25-30 million in damages. Or last year, a Jacksonville, Florida grew so large that it shut down a portion of nearby Interstate 295 and forced the local fire department to deploy 45 apparatus, including 14 engines and seven ladder trucks. In both of these cases, as well as other similar fires, there were two clear similarities:
According to a recent NFPA report, between 2013 and 2017, "fires in structures under construction caused an average of four civilian deaths, 49 civilian injuries, and $304 million in direct property damage annually." In the same report, it is noted that three out of every four construction fires occur in residential buildings. During the 5 year timeframe in the report, 42% of the direct property damage was caused by fires starting from electrical distribution and lighting equipment.
Fires in wood buildings are certainly not a new development, but over the last several building code cycles, various code changes have been enacted that allow for larger and more complex wood buildings. For example, in the 2015 IBC, the "podium" concept, where a wood-framed buildings can be constructed on top of a Type IA podium, allowing for an overall larger building, was expanded to allow multiple levels of Type IA construction beneath the podium. More recently, in the 2021 IBC, Type IV construction has been significantly expanded to now include three different sub-categories (Types IV-A, IV-B and IV-C), allowing for substantially taller and larger heavy timber buildings.
Without a doubt, there are numerous benefits to wood-framed construction. Reduced carbon emissions, faster construction and reduced building costs - all are positive reasons for designers to choose wood buildings. But the very nature of wood being a combustible material brings inherent risks, particularly during construction where fire protection systems are not yet in place.
How to Respond?
While recent code changes have allowed for larger and more complex wood buildings, requirements for safeguards during construction have evolved as well. For example, in the 2021 IBC, Chapter 33 has been updated with a few notable changes:
NFPA 241, Standard for Safeguarding Construction, Alteration, and Demolition Operations, does provide requirements that are often more stringent than IBC Chapter 33. But many jurisdictions do not adopt or enforce compliance with this standard.
Apart from the model codes, many local jurisdictions have enacted their own requirements. In addition to requirements for protection during construction, I am also seeing local requirements for pursuing phased occupancy, where building owners want to occupy a portion of a building while other areas are still under construction. For example, Fairfax County, VA publishes a standard operating procedure document for phased occupancy that institutes a variety of building and site requirements that have to be met before phased occupancy can be considered.
But even with national and local codes addressing the issue, the magnitude of these fire losses does force you to ask: Is enough being done?
What are you Seeing?
What trends are you seeing in your area? Does your local building or fire department have any specific requirements for fire protection during construction or phased occupancy, particularly for wood buildings? While I don't think there is a one size fits all solution to such a problem, I'm very interested in hearing a variety of perspectives from across the country. Please share in the comment section below!
If you are located in any major city, it’s likely that you can take a short walk down the street and find an instance of two adjacent buildings built up next to each other. If you’re out in the suburbs, you have probably seen this situation in the form of a row of townhouses. In the U.S., and other countries that adopt the International Building Code (IBC), these abutting buildings likely fall into one of the following cases:
In either case, the IBC recognizes three distinct approaches for the wall(s) located between the abutting buildings. All references are to the 2015 IBC.
Walls Between Abutting Buildings
Abutting Exterior Walls
In both cases described above, the IBC allows for two abutting exterior walls to separate the two buildings. Since the two buildings have a zero fire separation distance, IBC 602 requires both walls to have a 1-hour fire-resistance rating for most occupancies (the requirement is higher for Groups M, F-1, S-1 and H). Similarly, IBC 705.8 prohibits openings in either of these walls.
Since both structures are considered separate and distinct buildings, structural independence is required. Both exterior walls are prohibited from bearing on each other, and the walls must be supported and braced by their respective buildings. This strategy is common when the two buildings have tenants or occupants who are unrelated to one another. Since openings between the buildings are not permitted, this approach is not practical when doors between buildings are required.
Once common exception is a concrete parking structure that is surrounded on all sides by a residential building. This type of project, often referred to as a “wrapper building” or “Texas Donut," utilizes a newly-added provision in the 2015 IBC 705.3, which allows protected openings between the buildings, as long as the opening in the parking garage building has a 1.5-hour fire resistance rating. The opening in the residential building does not require an opening protective in this case.
Fire walls are required to be structurally independent from the building and must be continuous to the foundation. For two abutting buildings located on the same lot, this means that neither of the buildings can bear on the fire wall, which often results in the construction of three walls: the fire wall plus a separate exterior wall for each building. Floor assemblies can be connected to the fire wall using breakaway clips for continuity purposes, but they cannot be supported by the fire wall.
While the structural requirements for a fire wall are more restrictive than for exterior walls located near a lot line, fire walls are permitted to have protected openings. The openings in fire wall are limited to 156 SF, unless both buildings on either side of the fire wall are fully sprinkler-protected, in which case there is no limit to the area of openings (IBC 706.8). The required fire resistance rating of a fire wall is dependent on the occupancy classifications involved (IBC Table 706.4).
Beginning in the 2015 IBC, code language was added to allow for compliance with NFPA 221 to satisfy the requirements of IBC 706. NFPA 221 contains provisions to allow double fire walls (two rated walls built next to each other) in lieu of one structurally independent fire wall. As shown in NFPA 221 Table 4.5 (copied below), two walls, each with a 2-hour fire resistance rating are deemed equivalent to a single 3-hour fire wall.
This is similar to the abutting exterior wall strategy described previously, but the required wall rating is increased in order to meet the NFPA 221 requirements. Though this approach involves two separate walls, the entire assembly is considered a fire wall by the IBC. The fire wall strategy is best suited when there is a single owner or tenant in both buildings and openings between the two buildings are necessary.
The final option described in the IBC for the wall between two abutting buildings is a party wall. A party wall is described in the IBC as “Any wall located on a lot line between adjacent buildings, which is used or adapted for joint service between the two buildings…” (IBC 706.1.1).
This description indicates that party walls are specific to abutting buildings located on separate lots; a wall between buildings on the same lot would not be considered a party wall. Party walls must meet all of the requirements for fire walls, except that no openings are permitted. Generally, party walls require both owners to agree on how the wall will be used and any future design changes will be handled.
Abutting buildings can be found on the same lot or on two adjacent lots. Architects and engineers can choose between: (1) two abutting exterior walls, (2) a fire wall, or (3) a party wall when designing the wall between the two buildings. How have you approached designs in this situation? Comment and let us know!