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The Building Code Blog

Occupied Roof Decks - Code Changes in 2018 and 2021 IBC

3/26/2021

8 Comments

 
As more and more states move to adopt the 2018 IBC, it's important to know about a few code updates that impact the design of occupied roof spaces. And if you're jurisdiction is on the ball and already adopted the 2021 IBC, there are a few additional items that apply to you.
Picture
Occupied roof at the Facebook headquarters in Menlo Park, CA (image courtesy of Facebook).

Occupied Roofs Under the 2018 IBC

In the 2015 IBC and prior editions, the code remained silent in regards to occupied roof decks and requirements for allowable height and area.  Under the 2018 IBC, there are now specific provisions addressing this issue.

First, IBC 302.1 has been updated with specific requirements for classifying an occupied roof space:
Where a structure is proposed for a purpose that is not specifically listed in this section, such structure shall be classified in the occupancy it most nearly resembles based on the fire safety and relative hazard. Occupied roofs shall be classified in the group that the occupancy most nearly resembles, according to the fire safety and relative hazard, and shall comply with Section 503.1.4. (Excerpt from 2018 IBC 302.1)
This added language forces designers to classify an occupied roof with an occupancy, whereas some jurisdictions has not previously required it.

Next, IBC 503.1.4 brings in a major new requirement:
A roof level or portion thereof shall be permitted to be used as an occupied roof provided the occupancy of the roof is an occupancy that is permitted by Table 504.4 for the story immediately below the roof. The area of the occupied roofs shall not be included in the building area as regulated by Section 506.
This section limits the occupancy on an occupied roof to those allowed on the story immediately below the roof. So if your building construction type allows an assembly occupancy on the top story, you are also permitted an assembly occupancy on the roof. The code does offer two major exceptions:
  1. If your building if fully sprinkler-protected (NFPA or 13R) and you have fire alarm notification on the occupied roof, you are permitted to have any occupancy on the occupied roof.
  2. If your building is Type I or II construction, you are permitted to have assembly occupancies on the roof of parking garages.

Take the image below for an example, a 4 story building consisting of Type IIIA construction. If the building is fully sprinkler protected in accordance with NFPA 13, a Group A-3 occupancy would per permitted on Level 4. As long as occupant notification is provided on the roof, the 2018 IBC now explicitly allows a Group A-3 occupancy on the roof.
Picture
Sketch of a 4 story building with occupied roof. Assuming Type IIIA construction, fully sprinkler-protected with fire alarm notification throughout, a Group A-3 occupancy is now explicitly permitted on the roof.

​The provision of Section 503.1.4.1 do limit elements on the roof to no more than 48" above the roof surface, with exceptions for penthouses, tower, domes, spires and cupolas. If you have elements above this height, the roof would have to be classified as a story. As an example, the overhang in the image above of the Facebook building would likely trigger the roof being classified as a story.


Another common question is whether an occupied roof can trigger classification as a high-rise building.  The IBC itself does not address this issue, but this staff opinion from the ICC is very helpful in clarifying the intent.  The opinion clearly states, "Just because a roof is an occupied roof does not make it a floor with respect to the definition of a high-rise building. "

Occupied Roofs Under the 2021 IBC

The 2021 IBC updates Section 503.1.4 to explicitly clarify that an occupied roof should not be included when determining building height or number of stories per IBC 504. Language was also added to clarify that this only applies when penthouse and other rooftop structures, when present, comply with IBC 1511. This further supports the notion described above that an occupied roof should not by itself trigger a classification as a high-rise building.

Additionally, the 2021 IBC clarifies that the Exception 1 to 503.1.4 for occupant notification would only require a voice fire alarm system on the roof if the system is required elsewhere in the building. In other words, if you aren't required to have a voice fire alarm in the building, you don't have to provide it on the roof in order to use Exception 1.

Finally, the 2021 IBC updates Section 1511.2.2, Use Limitations for Penthouses, to specifically allow "ancillary spaces used to access elevators and stairways" to be considered part of a penthouse. This means that a stair or elevator tower to the roof will not force an occupied roof to be classified as a story, even though those elements are taller than 48" from the roof surface.
Picture
The 2021 IBC clarifies that spaces used to access an elevator or stairway providing access to the roof are permitted to be considered a penthouse, and therefore not a story (Image courtesy of Dana Schulz).
8 Comments

Fire Protection During Construction in Wood Buildings - What do you Think?

3/12/2021

12 Comments

 
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:
  • The building construction included wood structural members (Type III, IV or V construction)
  • The building sprinkler systems were not yet active
In large, wood-framed apartment buildings, the window of time between enclosure of the structure and the building sprinkler system being functional is a clear vulnerability. The presence of a huge fuel load without an active fire sprinkler systems is a dangerous situation, where a single ignition source can lead to horrific fire losses. 
Picture
The smoldering remnants of the Ely at Fort Apache apartment project (Image courtesy of Clark County Fire Department).
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.
Picture
A fire in Jacksonville, FL completed destroyed a 384-unit apartment building under construction (Image courtesy of Jacksonville Fire and Rescue Department).

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:
  • Updated requirements for water flow to construction sites of buildings of Type III, IV and V construction. Depending on the size of the building and the fire separation distance, the flow requirements start at 500 gpm and continue up to the full required fire flow for the building when constructed (IBC 3313).
  • Updated requirements for fire watch during construction, specifically authorizing the fire code official to require a fire watch for buildings exceed 40 feet in height when the area per story exceeds 50,000 square feet (IBC 3315.1).

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!
12 Comments

New Stair Pressurization Estimator

3/5/2021

0 Comments

 
While working in the early phases of a project, a mechanical engineer recently asked for an estimate of the required stair pressurization system fan capacity. On this particular project, I am planning to do a CONTAM analysis, but won't start that portion until later in the Design Development phase.

Since I wanted to give the mechanical engineer an estimate for sizing purposes, I put together a quick calculator to estimate the fan size. Check it out at the link below!
Picture

    Check out the Stair Pressrization Estimator

Go to the Tool
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The views, opinions, and information found on this site represent solely the author and do not represent the opinions of any other party, including the author's employer and the International Code Council, nor does the presented material assume responsibility for its use.  Local codes and amendments may vary from the code requirements described herein. Fire protection and life safety systems constitute a critical component of public health, safety and welfare and you should consult with a licensed professional for proper design and code compliance.
  • Home
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  • Tools
    • Allowable Height & Area Calculator - Separated Mixed Occupancy
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    • Fire and Smoke Damper Tool
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    • IBC Occupant Load Calculator
    • Plumbing Fixture Calculator
    • Stair Pressurization Estimator
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