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Key Takeaway: Winder stairs are generally limited to dwelling units or very small spaces, unless the stair can meet the more restrictive requirements for curved stairways. Winder stairs, or specifically, winder treads, are a unique architectural feature that an architect or engineer can use when designing a stairway. The International Building Code (IBC) has several limitations on the use of winder treads through, restricting the situations where they can be used. In this post, we are going to explore the code requirements for winder treads to determine how they need to be designed and where they can be used. All references are to the 2021 IBC. If you are working on a one or two family dwelling, a separate set of requirements from the International Residential Code (IRC) likely applies. What is a Winder Stair?A winder stair is a stair consisting of winder treads. A winder tread is defined in the IBC as “a tread with nonparallel edges.” In a traditional stair, the opposite edges of each tread are parallel, meaning the tread is rectangular in shape. In a winder stair, the opposite edges are not not parallel, so the tread forms a trapezoidal shape. Winder Tread Requirements (IBC 1011.5.2) Winder treads are required to have a minimum depth of 11 inches, measured at the walkline. IBC 1011.4 defines the walkline as the line located 12 inches from the side of the tread where the winders are narrower. Additionally, the winder tread is required to have a minimum depth of 10 inches anywhere within the clear width of the stair, including inside of the walkine. Similar to regular stairs, the maximum riser height for a winder stair is 7 inches.  Dimensional requirements for winder treads. There are several exceptions to the above requirements: In Group R-2 dwelling units and Group R-2 occupancies, the minimum winder tread depth at the walkline is reduced to 10 inches and minimum winder tread depth anywhere in the clear width is reduced to 6 inches. Riser heights in this situation are permitted to be a maximum of 7.75 inches. In spiral stairways, the minimum winder tread depth at the walking is reduced to 6.75 inches at the walkline. The maximum riser height is 9.5 inches and the minimum clear width is 26 inches for spiral stairs. And finally, curved stairways must comply with the IBC 1011.5.2 requirements, plus the inner radius of the stair must be at least twice the required width of the stair itself.  Dimensional requirements for winder treads within a curved stairway. The inner radius is also required to be at least twice the required width of the stairway. Where are Winder Treads Permitted (IBC 1011.5.3)?For projects under the IBC, there are limited situations where winder treads can be provided. Generally, winder treads cannot be used as part of a required egress stairway, except when located within a dwelling unit. There are two exceptions: curved stairways and spiral stairways. Curved stairways can be used anywhere in a building, but many designers will not choose this option due to the large required radius of the stair. Spiral stairways can only be used in the following situations:
SummaryWinder stairs are generally limited to dwelling units or very small spaces, unless the stair can meet the more restrictive requirements for curved stairways.
When provided, winder treads must be a minimum of 11 inches in depth at the walkline and 10 inches in depth inside the walkline, with some reductions in depth for dwelling units and spiral stairs.
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**Updated 2/9/2023 with IBC 2021 Code References and new images! About twice a year, I receive a question from an architect regarding safety glazing. Where is it required? Can I provide a different type of glass? Is this manufacturer/model acceptable? Without fail, I always end up revisiting the International Building Code (IBC) to review the requirements before answering the question. So in an effort to save me (and hopefully you) time in the future, I have compiled a quick reference guide for safety glazing. All references are to the 2021 IBC. Safety GlassPractically, safety glazing refers to glass panels or other materials that are manufactured to reduce the likelihood of breaking and to minimize the safety risk if the material does break. From a code compliance standpoint, safety glazing refers to any glazing that meets the requirements of IBC 2406. Glass panes are the most common safety glazing material, but the IBC also recognizes plastic, glass block, and louvered windows as potential options. The IBC does not provide any requirements for the process used to manufacturer safety glazing, it only provides performance requirements. Therefore, both tempered and laminated glass assemblies can qualify as safety glazing, if they meet the IBC 2406 requirements. Tempered Glass vs. Safety GlassOne common misunderstanding is confusing tempered glass with safety glass. As explained below, tempered glass is one type of safety glazing, but not the only type. The building code requirements explained below do not require tempered glass (only safety glass), but tempered glass can be used when safety glass is required. Where is Safety Glass Required?IBC 2406.4 identifies 7 locations as hazardous locations that require safety glazing: Glazing in Doors (IBC 2406.4.1): Glazing in any fixed or operable panels of swinging, sliding and bifold door is considered a hazardous location. Exceptions include:
Glazing Adjacent to Doors (IBC 2406.4.2):Glazing within 24” horizontally from a door where the bottom of the glazing is less than 60” above the floor is considered a hazardous location. Exceptions include:
 Diagram of required safety glazing locations in doors and adjacent to doors. Glazing in Windows (IBC 2406.4.3): Glazing where a panel is greater than 9 square feet in area where the bottom is less than 18” from the floor, top is greater than 36” from the floor and within 36” of a walking surface is considered a hazardous location. Exceptions include:
 Diagram of required safety glazing locations in windows. Glazing in Guards and Railings (IBC 2406.4.5):Glazing in any guard, railing, balaster panel and in-fill panel is considered a hazardous location. Glazing in Wet Areas (IBC 2406.4.5):Glazing in areas containing hot tubs, spas, whirlpools, saunas, steam rooms, bathtubs, showers and swimming pools where the bottom is less than 60” from the walking surface. There is an exception for when the glazing is more than 60” horizontally from the water’s edge of a bathtub, hot tub, spa, whirlpool or swimming pool. Glazing Adjacent to Stairways and Ramps (IBC 2406.4.6): Glazing near stairways and ramps where the bottom is less than 60” above the walking surface is considered a hazardous location. Exceptions include:
 Diagram of required safety glazing locations adjacent to stairways. Glazing Adjacent to the Bottom of a Stairway Landing (IBC 2406.4.7):Glazing near the landing at the bottom of a stairway where the bottom is less than 60” above the landing and within 60” horizontally at an angle of less than 180 degrees from the bottom tread nosing is considered a hazardous location. There is an exception for glazing protected by a guard where the glazing is at least 18” from the guard.  Diagram of required safety glazing locations adjacent to the bottom of stairways. Glazing in Rated Assemblies (IBC 716.1.2.1):Additionally, glazing located in fire-protection rated or fire-resistance rated glazing installed in fire door and window assemblies is required to be safety glazing. Design OptionsWhen safety glazing is required, the most common design option is manufactured glazing panels that are either laminated or tempered. Safety glazing panels are required to be tested to either CPSC 16 CFR Part 1201 or ANSI Z97.1 and must be identified through a label or other means of designation. There is an exception that allow forms of safety glazing other than tempered glass to not be labelled when approved by the AHJ. When tempered glass is used, the glazing must be identified by a manufacture’rs designation that is, “acid etched, sand blasted, ceramic fired, laser etched, embossed, or of a type that once applied, cannot be removed without being destroyed.” In retrofit applications, it may not be desirable to replace existing glazing with new safety glazing panels. There are various film products available that can be applied to existing glazing that will satisfy the code requirements for safety glazing. Some examples include products by 3M, Llumar and Gordon Glass. If using this option, it’s important to determine who applies the label to the glazing once the film is applied. If the installing contractor is applying a label after the film is installed, check with the local authority to verify that this will be acceptable. Since the IBC has fairly stringent requirements on safety for identification of the safety glazing, some AHJs require a permanent label that is etched in to glass. ConclusionThere are 7 distinct hazardous areas where the IBC requires safety glazing. Technically, any product that meets the requirements of IBC 2406 can be considered safety glazing, but the most common products are tempered and laminated glass. Be sure to verify that the product you select has been tested in accordance with CPSC 16 CFR Part 1201 or ANSI Z97.1
Key Takeaway: The IRC and IBC both provide a variety of requirements for stairways and staircases, including minimum width, minimum and maximum riser/tread dimensions, minimum headroom height and maximum total rise. A stairway is a key part of the means of egress for any multi-story building or structure. Also known as a stair or staircase, stairways provide a path for occupants to traverse from one level to another within a building or space. In this post, we’ll review some of the key requirements for stairways from both the International Residential Code (IRC) and the The International Building Code (IBC). All references are to the 2021 editions of these codes.  An interior open stairway. What is a Stairway?There are two key definitions here that are important to understand: Stair and Stairway. Both the IRC and IBC defines these terms as follows: Stair: “A change in elevation, consisting of one or more risers.” Stairway: “One or more flights of stairs, either exterior or interior, with the necessary landings and platforms connecting them, to form a continuous and uninterrupted passage from one level to another.” So a stair is simply the change in elevation that is created by one or more risers, while a stairway includes both the stairs and the required landing and platforms. Note that the term “staircase” is frequently used when referring to a stairway, but neither code actually uses this term. If you are working on a project that contains an unenclosed stairway (also known as an open stairway), be sure to check out this post on additional requirements. Minimum Width for IRC Stairways (R311.7)For projects falling under the IRC, the minimum stair width is 36 inches. The minimum width must be provided at all points above the permitted handrail height and below the required headroom height (meaning walls or other protruding objects cannot decrease this minimum width). Any provided handrails cannot protrude more than 4.5 inches into the minimum width. So if a handrail is provided on one side, the minimum clear width is 31.5 inches and if a handrail is provided on both sides, the minimum clear width is 27 inches. Note that the following stairways are not required to meet the minimum width requirements:
 Stair width and handrail requirements from the 2021 IRC. Minimum Width for IBC Stairways (1011.2)For projects falling under the IBC, there are two width requirements that apply: minimum width and required capacity. Generally, the minimum stair width is 44 inches, unless the stairway serves an occupant load of less than 50, in which case the minimum width is 36 inches. Note that if the stairway is serving as an accessible means of egress, the minimum width between handrails is 48 inches, unless the building is fully sprinkler-protected or the stairway is provided with an area of refuge. Check out this article for more information on the required means of egress vs. accessible means of egress. Note that the following stairways are not required to meet the minimum width requirements:
The second width requirement is the required egress capacity of the stairway (IBC 1005.3.1). The required capacity is determined by multiplying the occupant load using the stairway by a capacity factor of 0.3 inches per occupant. In other than Group H and Group I-2 occupancies, this factor is reduced to 0.2 inches per occupant when the building is fully sprinkler-protected and equipped with a voice fire alarm system. There are also reductions available for open-air or smoke-protected assembly seating spaces. Note that for multi-story buildings, only the occupant load of each individual story is considered when calculating the required capacity for each stair, not the cumulative occupant load using the stair. Similar to the IRC, the IBC allows handrails to project a maximum of 4.5 inches into the required width. So for a stair with handrails on each side that has a minimum required width of 44 inches, the minimum width between handrails would be 35 inches. Handrail HeightIn both the IRC and IBC, handrails are required to be located a minimum of 34 inches and a maximum of 38 inches above the stair. Specifically, this dimension is measured vertically from the stair tread nosing. Note that when handrails are transitioning between flights or at the start of a stairway, the fitting and bendings are permitted to exceed the maximum height.  Stair width and handrail requirements from the 2021 IBC. Stair Treads and Risers (R311.7.5)For projects falling under the IRC, the minimum tread depth is 10 inches, plus a required nosing of at least ¾ inch. If a tread of at least 11 inches is provided, there is no required nosing. The maximum permitted nosing is 1.25 inches. In any stairway, the tread depth and nosing depth have a maximum permitted variation of ⅜ inch. Note that under the IRC, the tread depth is measured horizontally between the vertical planes of the foremost projection of adjacent treads and at a right angle to the tread's leading edge. The maximum riser height is 7.75 inches, with a similar maximum permitted variation of ⅜ inch in any single stairway. Risers must be vertical or have a maximum slope of 30 degrees from vertical.  Stair dimensional requirements from the 2021 IRC. Stair Treads and Risers (1011.5.2)For projects falling under the IBC, the minimum tread depth is 11 inches. There is no requirement to provide a nosing, but the maximum nosing projection is 1.25 inches. Note that under the IBC, the tread depth is measured horizontally between the vertical planes of the foremost projection of adjacent treads and at a right angle to the tread's nosing. The IBC requires stairs to have a minimum riser height of 4 inches and a maximum height of 7 inches. Note that the following stairways are not required to meet the minimum riser/tread requirements:
 Stair dimensional requirements from the 2021 IBC. Headroom RequirementsBoth the IRC and IBC have similar requirements for headroom clearance. In both codes, the minimum headroom clearance is 80 inches, measured vertically from a line connected to the edge of each nosing. Both codes have exceptions for spiral stairways and where the nosings of treads at the side of a flight extend under the edge of a floor opening through which the stair passes (limited to Group R-2 dwelling units and Group R-3 in the IBC). Vertical Stairway RiseUnder the IRC, a single flight of stairs can have a maximum vertical rise of 12 feet 7 inches between floor levels or landings (R311.7.3). Under the IBC,the maximum rise is 12 feet (1011.8). SummaryThe requirements for stairways depend on whether your project falls under the IRC or IBC.
For IRC Stairways: Minimum Width = 36” Maximum Handrail Projection = 4.5” each side Minimum Tread Depth = 10” Minimum Nosing = ¾” or provide 11” tread Maximum Nosing = 1.25” Maximum Riser Height = 7.75” Minimum Headroom = 6’-8” Maximum Stairway Rise = 12’-7” For IBC Stairways: Minimum Width = 44” or 36” for smaller occupant loads. See also required capacity requirements. Maximum Handrail Projection = 4.5” each side Minimum Tread Depth = 11” Minimum Nosing = Not Required Maximum Nosing = 1.25” Minimum Riser Height = 4” Maximum Riser Height = 7” Minimum Headroom = 6’-8” Maximum Stairway Rise = 12’ Key Takeaway: Egress windows are required in all sleeping rooms for projects falling under the IRC and in many sleeping rooms for projects falling under the IBC. When required, the openings must meet specific egress window sizing requirements, and when provided below grade, must open into an area well. If you are working on a residential design or construction project, an important design consideration is the requirement for egress windows. While most people in the design community understand what you are referring to with this term, “egress windows” is not actually defined in the code. The International Building Code (IBC) and International Residential Code (IRC) both refer instead to Emergency Escape and Rescue Openings (EEROs). In this article, we’ll refer to egress windows and EEROs interchangeably, but remember that the code only defines EEROs. A window can be used to meet the EERO requirements, but doors and other openings are also an option. All references are to the 2021 IBC and IRC.  A basement emergency escape and rescue opening (egress window). What is an Egress Window?Egress Windows, or as the code calls them, EEROs, are defined in the IBC as “an operable exterior window, door or other similar device that provides for a means of escape and access for rescue in the event of an emergency. Essentially, an egress window or EERO is a way for a building occupant to escape in the event of an emergency or for a first responder or other personnel to access a building for the purposes of rescue. A fire is the obvious emergency that comes to mind, but the openings could be used for any emergency situation. When are Egress Windows Required?If you are working on a residential project in the United States, your building likely falls under one of two codes: the International Building Code or the International Residential Code. While the adoption of these codes varies by State and local jurisdiction, generally the IBC applies to apartments and larger residential facilities while the IRC applies to one and two family dwellings and townhouses. Many jurisdictions amend these codes, so be sure to check the applicable code enforced by your local authority having jurisdiction. IBC RequirementsIf your project falls under the IBC, emergency escape and rescue openings are required in the following occupancies (IBC 1031.2):
If you meet either of these conditions, then the IBC requires you to provide emergency escape and rescue openings in any basement or sleeping room below the fourth story above grade plane. There are numerous exceptions where EEROs would not be required:
IRC RequirementsIf your project falls under the IRC, Emergency Escape and Rescue Openings are required in basements, habitable attics and every sleeping room. If the basement contains more than one sleeping room, an EERO is required in each sleeping room (IRC 310.1). There are numerous exceptions where EEROs would not be required:
Egress Window Sizing RequirementsBoth the IBC and IRC have the same dimensional sizing requirements for EEROs:
 Dimensional requirements for emergency escape and rescue openings. These dimensions are required to be a result of the normal operation of the window or door - you cannot break or alter the window/door in order to achieve the required dimensions. Basement Egress WindowsArea wells are required to be a minimum of 9 square feet in area with a minimum dimension of 36 inches in both length and width. The area well must also be of sufficient size to allow the EERO to fully open. If the area well has a depth of more than 44”, a ladder or steps are required. The egress window or door opening into the area well cannot obstruct the ladder or steps when fully open.  Dimensional requirements for area wells. If you choose to provide a ladder for the area well, the ladder must have an inside width of at least 12 inches, must project at least 3 inches from the area well wall and the ladder rungs must be spaced no more than 18 inches apart for the entire height of the area well. If you choose to prove steps for the area well, the steps must have a minimum width of 12 inches, a minimum tread depth of 5 inches and a maximum riser height of 18 inches for the entire height of the area well. Finally, area wells are required to be connected to the buildings foundation drainage system unless the building is located on well-drained soil or sand-gravel mixture soils as defined by IBC 1803.5.1 and IRC 405.1 Bars, Grilles, Covers and Screens over Egress Windows When bars, grilles, covers, screens or other similar devices are placed over EEROs or area wells, these devices cannot reduce the minimum required dimensions described above. Additionally, the bar, grilles, cover or screen must be releasable or removable from the inside without a key or tool and cannot require a greater force than what is required to open the EERO itself. SummaryEgress windows, which the code refers to as “Emergency Escape and Rescue Openings” (EEROs) are required in all sleeping rooms for projects falling under the IRC and in many sleeping rooms for projects falling under the IBC.
When required, EEROs must meet the following size requirements:
If the EERO is below grade level, a minimum 36” x 36” area well is required. If the area well is more than 44” deep, a ladder or steps are required. **Updated 11/11/2022 with final ICC results and an updated cheatsheet. This week, the ICC Committee Action Hearings (CAH) kicked off, where proposed code changes for the 2024 ICC Codes are heard by the various ICC committees. In yestereday's session, the IBC General committee heard several proposed changes related to occupied roofs and the classification of high-rise buildings. In recent code cycles, there have been several key changes to occupied roof requirements, but none of these have addressed whether an occupied roof over 75' would trigger classification of a high-rise building. As a quick reminder, the 2021 IBC currently defines a high-rise building as "A building with an occupied floor located more than 75 feet above the lowest level of fire department vehicle access."  If the current proposed code change moves forward, an occupied roof like this one could trigger classification as a high-rise building. While previous code editions have remained silent on the issue, the ICC website does have two articles addressing high rise classification due to an occupied roof. This article, authored by ICC staff member Chris Reeves, clearly states that an occupied roof is not intended to count as a floor for the purposes of evaluating the high-rise building definition. Another article, authored by ICC staff member Kimberly Paarlberg, states "What has not yet been clarified is if an occupied roof is considered an occupied floor when determining if the building does or does not have to meet the high-rise provisions in the code..." While the two articles above are both informal opinions from ICC staff, it appears the 2024 IBC will now address this issue directly. During today's hearing, the IBC General Committee voted in favor of proposal G15-21, which is copied below: Revise as follows: [BG] HIGH-RISE BUILDING. A building with an occupied floor or occupied roof located more than 75 feet (22 860 mm) above the lowest level of fire department vehicle access. This proposed change to the definition of a high-rise building would require any building with an occupied roof above 75' to meet all of the high-rise building requirements. Several proposals, including G12-21 and G14-21, were aimed the other way, attempting to clarify that an occupied roof would not trigger a high-rise classification. Both of these were disapproved by the committee. When a building is classified as a high-rise, there are numerous additional requirements, including:
What Do You Think?Do you agree with the General Committee on this issue? Should an occupied roof above 75' trigger the classification as a high rise building? Please share your thoughts in the comments section!
Update 11/11/2022: This proposed change has been approved and will be included in the 2024 IBC. In projects of Type II, III, IV or V construction, architects are often forced to balance the allowable area limits of lesser construction types and the added cost of higher construction types. A fire wall is an ideal solution, as it allows for the cost savings of a lower construction type while allowing the structure on either side of the fire wall to be considered independently from an allowable area standpoint. On several recent projects, I have seen plan reviewers treat any door opening in the fire wall as a horizontal exit, even if that was not the design team’s intention. The reviewers then issued review comments regarding compliance with the horizontal exit code requirements. This has led me to the question: is an opening in a fire wall automatically a horizontal exit?  A pair of opposing doors in a fire wall. Before I get to my answer, you might be asking: why does this matter? Horizontal exits come with several code requirements, but in the recent projects I mentioned, the plan reviewers were citing the following: Exit CapacityPer IBC 1026.1, a horizontal exit can provide up to one half of the total number of exits, total exit width and total egress capacity. So if the door in the fire wall is a horizontal exit, then it can not be providing more than half of the required number of exits or required exit width.If you have a single door in the fire wall and then an exit stair on either side, this is no problem. But once you have multiple doors in the fire wall, the horizontal exit can easily exceed one half of the total required exits/width. Refuge AreasPer IBC 1026.4, when a horizontal exit approach is used, a refuge area is required in the space on the other side of the horizontal exit. This refuge area must be large enough to accommodate the original occupant load of the space plus 3 square feet for each occupant entering into the refuge area from the horizontal exit. Depending on the building arrangement and capacity, providing this refuge area may be a design challenge. Standpipe Hose ConnectionsPer IBC 905.4.2, a standpipe hose connection is required on each side of a horizontal exit. An exception does exist if the floor areas adjacent to the horizontal exit are within 130’ of standpipe hose connection with an exit stair. So if any door in a fire wall is a horizontal exit, each of these code requirements must be met, adding additional cost and design coordination. Coming back to the original question: Is an opening in a fire wall automatically a horizontal exit?I believe the answer is no. A door opening in a fire wall can be a horizontal exit, but it is not required to be a horizonal exit. My opinion is based on a few factors. First, let’s look at the definition of fire wall (IBC Chapter 2): A fire-resistance-rated wall having protected openings, which restricts the spread of fire and extends continuously from the foundation to or through the roof, with sufficient structural stability under fire conditions to allow collapse of construction on either side without collapse of the wall.” This definition does not mention or describe a horizontal exit at all. Similarly, we can go to IBC Chapter 5, where the general requirements for building height and area are given. Per IBC 503.1: For the purposes of determining area limitations, height limitations and type of construction, each portion of a building separated by one or more fire walls complying with Section 706 shall be considered to be a separate building.” This statement indicates that a fire wall creates separate buildings for the purposes of allowable height/area and construction type, but again, it does not mention or describe a horizontal exit. Finally, if we return to the horizontal exit section of IBC Chapter 10, we see in Section 1026.2 that a horizontal exit is permitted to be provided as either a fire wall or a fire barrier. No where in this section is a fire wall required; it is just given as one of two options. I have never heard of any AHJ requiring all fire barriers to be a horizontal exit, so why would we apply that logic to fire walls? Icing on the Cake: An ICC Committee Interpretation I am not the first person to ask this question, and fortunately, the ICC released a committee interpretation on this same issue a few years ago. To summarize the committee’s interpretation, fire door openings in a fire wall are not required to be considered as a horizontal exit unless the design of the egress system intends to utilize the provisions of a horizontal exit. ConclusionWhile you would think that the code support described above, plus an ICC committee interpretation would be sufficient to persuade any AHJ, I have still experience pushback on this issue from plan reviewers.
Despite this, I believe the intent of the code is to allow a door in a fire wall to be used as a horizontal exit, but not require it. And if the design intention is not to utilize the horizontal exit provisions, then you do not need to be concerned about the exit capacity restrictions, refuge area requirements and additional standpipe hose connections that I described previously. Have you encountered a similar issue before? If so, please comment below and let me know. I work on a variety of multi-family housing projects, including residential apartment buildings and senior living facilities, where each dwelling unit has its own washer and dryer. In the past, I have always seen the dryer exhaust duct routed through a wall and then into the cavity of a floor-ceiling assembly, but on a recent project, the local AHJ questioned the validity of this approach. Code Requirements for Dryer Vent InstallationThis post is a summary of the code requirements and my suggestions for the most straight-forward way to handle the situation. All code references are the 2021 ICC Codes. Challenge 1: No Dampers PermittedThe first challenge when approaching dryer exhaust ducts is that the International Mechanical Code (IMC) Section 504.2 specifically prohibits the installation of fire dampers or combination fire/smoke dampers. If your dryer exhaust duct does not penetrate a rated wall or floor assembly, then you likely have no issue. However, since no one wants to look at a dryer exhaust duct running through their apartment, most designers choose to route the duct into the ceiling and then out of the building. This leads us to challenge 2. Challenge 2: Dampers Required at Floor/Ceiling Penetrations A duct that penetrates the ceiling of a floor/ceiling assembly and then runs horizontally through the floor cavity and out of the building would be considered a membrane penetration. IMC Section 607.6.2 requires that duct membrane penetrations of a rated floor/ceiling or roof/ceiling assembly be protected with either a listed ceiling radiation damper or a shaft enclosure (there is a similar requirement in IBC Section 717.6.2). We already know from our first challenge that a damper is not permitted, so that seemingly leaves a shaft enclosure as the only option. Again, it’s undesirable to building residents or designers to have a shaft enclosure simply to protect a dryer exhaust duct. Solution: Dryer Vent InstallationFortunately, a straight-forward solution is found in IBC 717.6.2.2, Exception 2. The exception here allows for the omission of a damper at the ceiling membrane penetration when the duct is protected in accordance with IBC Section 714.5.2, is located within the cavity of a wall and does not pass through another dwelling unit or tenant space. Our situation meets the last two requirements, as the duct is first routed into a wall prior to running through the ceiling cavity, where it then is routed horizontally to the exterior, without passing through another dwelling unit. For the first requirement, IBC Section 714.5.2 states that membrane penetrations of horizontal assemblies must comply with 714.5.1.1 or 714.5.1.2, which give requirements for through-penetration firestop systems. This section also offers 8 different exceptions.  Detail showing the membrane penetration permitted by IBC 717.6.2.2, Exception 2. Before we get into those exceptions, though, it’s important to point out that running the dryer exhaust duct through a wall and into the ceiling cavity presents us with another code question: how do we address the intersection of the wall and rated floor/ceiling assembly? If the top of the wall is located completely below the ceiling membrane of the rated floor/ceiling or roof/ceiling assembly, there is no issue. However, this arrangement is difficult to construct, particularly in wood construction, as it would require a continuous ceiling running past the top of the wall. Most of the time, the top of the wall interrupts the ceiling membrane, meaning the ceiling stops on one side of the wall and continues on the other side. This arrangement would itself be considered a membrane penetration of the floor-ceiling or roof-ceiling assembly, even without a dryer duct present. IBC Section 714.5.2 Exception 7 addresses this exact situation: The ceiling membrane of a maximum 2-hour fire-resistance-rated horizontal assembly is permitted to be interrupted with the double wood top plate of a wall assembly that is sheathed with Type X gypsum wallboard, provided that all penetrating items through the double top plates are protected in accordance with Section 714.5.1.1 or 714.5.1.2 and the ceiling membrane is tight to the top plates.” This exception allows for the wall to interrupt the ceiling membrane as long as it is provided with a double wood top-plate that is tight to the ceiling and sheathed with Type X gypsum board. Note that this section does not require the wall to be rated. Additionally, the exception requires that the duct be protected in accordance with Section 714.5.1.1 or 714.5.1.2 (the same through penetration firestop sections referenced earlier). For my specific project, the building is a wood-framed structure, so there was no issue in providing a double top plate for each wall. In buildings of Type I or II construction, this would still be a valid approach as long as the wall itself is not a bearing wall and fire-retardant treated wood is used for the double top plate (IBC Section 603.1, Item 1.1). The final code section here, IBC Section 714.5.1.2, requires an approved through penetration firestop system with F and T ratings of at least 1 hour but not less than the rating of the floor itself. Exception 1 of this section eliminates the requirement for the T rating when the penetration is located within the cavity of a wall. This requirement forces us to find a listed fire-stop assembly that matches out proposed conditions. There are numerous assemblies available, particularly through companies such as Hilti or 3M. If you are tracking the code path through the mechanical code, the path is shorter, but the end result is the same. IMC Section 607.6.2, Exception 2 allows for the omission of a damper at the ceiling membrane penetration when the duct is protected in accordance with IBC Section 714.5.1.2, is located within the cavity of a wall and does not pass through another dwelling unit or tenant space. Note the subtle difference in section here compared to IBC Section 717.6.2.2 Exception 2 – the IMC takes you directly to the through penetration firestop requirement. See the flow chart below comparing the code path through both the IBC and IMC.  Comparison of the IBC and IMC code paths. Potential Challenge with Firestop System On the recent project where this issue came up, every firestop assembly for this configuration that I found stated that the dryer duct could be located within a wall, but when the wall was used, it had to be a minimum 1-hour rated wall. This was a challenge because the proposed configuration for my project involved the dryer exhaust duct running through an interior dwelling unit wall which was not rated. After a few hours of digging through the UL firestop database, I could not find a single listed firestop system that described a duct running through a non-rated wall and then into a 1-hour floor/ceiling assembly. This was a surprising result, as the IBC clearly does not require the wall to be rated when using Section 714.5.2 Exception 7. I ended up pursuing an Engineering Judgment to address the situation. ConclusionBoth the IBC and IMC provide code paths to route a dryer exhaust duct through wall, into a rated floor/ceiling or roof/ceiling assembly, and then out of the building. A listed firestop assembly is required to address the penetration of the duct through the ceiling membrane. If you happen to be running your duct through a rated wall, there are numerous firestop assemblies readily available for this configuration. If you are running the duct through a non-rated wall, you will likely need an engineering judgement. If you have found a listed firestop assembly that allows for a non-rated wall in this scenario, please let me know!
As I have spent time in existing buildings over the years, whether surveying a building for potential renovations, reviewing existing conditions or doing inspections, the concept of the building “meeting code” often comes up. Building owners, building maintenance staff, or anyone that is concerned with the operation or maintenance of a building wants to know if their building is up to code. Unfortunately, “meeting code” can mean several different things, and it is easy to lose track of which codes actually apply to an existing building. Does the International Building Code apply? Or is the International Existing Building Code? Or both? In this post, we’ll explore the various building and fire codes that could apply to your existing building. There are many other codes (e.g. electrical, elevator) that we won’t specifically address, but the general thought process for those is similar. All references will be to the 2021 ICC codes, but many states and local jurisdictions modify these requirements, so be sure to verify the specific requirements for your area. Note: If your building is a one or two family dwelling or a townhouse, the International Residential Code (IRC) is likely the applicable code. The IBC and IEBC typically do not apply to such buildings. Existing Building Scenario 1: Normal OperationsIf you have an existing, permitted, occupied building that is proceeding with normal operations (meaning there is no construction activity occurring and you are not changing the use or occupancy of the building from the original design), “meeting code” is fairly simple. IBC/IEBC ComplianceFirst, the International Building Code (IBC) and International Existing Building Code (IEBC) generally do not apply to your building. The application of both codes is limited to situations where some level of work is occurring to the building. For example, IBC 102.3.2 states: The legal occupancy of any building existing on the date of adoption of this code shall be permitted to continue without change, except as otherwise specifically provided in this code, the International Fire Code or International Property Maintenance Code, or as is deemed necessary by the building official for the general safety and welfare of the occupants and the public. In other words, the IBC does not require any change to your building unless there is a specific requirement in the International Fire Code (IFC), International Property Maintenance Code (IPMC), or the code official determines there is a required change necessary because of a threat to public safety. We’ll get to the IFC and IPMC shortly, but the final point is an important one to note. The code language does give the Building Code Official the authority to require a change to your building if they deem it is necessary for safety reasons. In my experience, this authority is typically reserved for use when there is a clear danger to occupant safety. As a hypothetical example: if your building has an exit stairway that does not have any handrails, even though it was permitted that way from the beginning, the code official could deem the lack of handrails a big enough safety risk that they require you to install them. Assuming your building does not have any blatant safety risks, though, it’s unlikely that the code official would use this language to force a change in your building. Similar to IBC Section 102.3.2, the IEBC has the exact same language in Section 101.4. Additionally, the overall scoping language in IEBC 101.2 states that the provisions of the IEBC apply to the “repair, alteration, change of occupancy, addition to and relocation of existing buildings.” So if you are not performing any of those actions on your building, the IEBC does not apply. What about NFPA 101?If you are in a jurisdiction that adopts NFPA 101, there are additional requirements you need to consider. Unlike the ICC, which separates the IBC and IEBC into two different codes, NFPA 101 applies to both new and existing buildings. For example, NFPA 101 Section 7.1.1 states “Means of egress for both new and existing buildings shall comply with this chapter.” NFPA 101 Chapters 7-11 all apply to both new and existing buildings, so you’ll need to review these chapters for specific existing building requirements that could apply to your situation. After Chapter 11, NFPA 101 contains occupancy-specific chapters that only apply if those occupancies are in your building. These chapters alternate between new and existing occupancies (for example, Chapter 12 applies to new assembly occupancies and Chapter 13 applies to existing assembly occupancies). So the requirements found in any of the applicable “existing” chapters in NFPA 101 would also apply to your building. IFC ComplianceSecond, certain portions of the IFC will apply to your building. The application of the IFC is divided into two categories:
IFC Construction and Design RequirementsPer IFC Section 102.1, the construction and design provisions of the IFC “apply to:
In our Scenario 1 case, Items 1 and 2 would not apply since we are an existing, permitted building. Items 3 and 4 would apply, though. Item 3 sends us to IFC Chapter 11, and, Item 4, similar to the IBC, gives the code official authority to enforce the IFC on existing buildings if they deem there to be a distinct hazard to life or property. IFC Chapter 11 primarily focuses on fire safety and means of egress requirements. A few examples include:
These requirements are fairly basic and typically are not difficult to achieve, but this would be a good section to thumb through to determine if they apply to your building. IFC Section 1103.1 details which sections of Chapter 11 apply based on the use and occupancy classifications in your building. IFC Administrative, Operational and Maintenance ProvisionsPer IFC Section 102.2, the administrative, operational and maintenance provisions of the IFC “apply to:
In our Scenario 1 case, both of these items apply. This means you’ll need to review the IFC chapters that are relevant to the given system or component of your building under consideration to determine if there are any applicable requirements. For example, if you are working with a dry-cleaning facility, there are requirements in IFC Chapter 21 that would apply to how you operate the facility and equipment. What about NFPA 1?If you are in a jurisdiction that adopts NFPA 1 in lieu of the IFC, you’ll have a little more work to determine what applies to your building. Similar to NFPA 101, NFPA 1 applies to both new and existing buildings and contains requirements for existing buildings throughout the code. You’ll need to review the chapters that are relevant to the given system or component of your building under consideration and then find the requirements for existing buildings located within those relevant chapters. Existing Building Scenario 2: Changing an Existing BuildingIf you are performing work on your building, there are additional code requirements beyond those described for Scenario 1. IEBC ComplianceThe IEBC is your first stop for determining the applicable code requirements. IEBC Section 101.2 states that the provisions of the IEBC apply to the “repair, alteration, change of occupancy, addition to and relocation of existing buildings.” So you first want to review the definitions of each of these terms in IEBC Chapter 2 and determine which apply to the work you are performing in your building. For repair work, the requirements of IEBC Chapter 4 apply. The general intent of this chapter is to maintain the existing level of code compliance in the building (at a minimum), though there are some specific additional requirements depending on the system or component undergoing repair. For relocated building, the requirements of IEBC Chapter 14 apply. For the other IEBC work classifications: alterations, changes of occupancy and additions, there are three potential compliance paths:
Prescriptive Compliance MethodThe prescriptive compliance method essentially requires the work being performed to comply with the requirements of the IBC, with a few exceptions involving situations where IBC compliance is unfeasible for an existing building. For many existing buildings, the requirements of the current edition of the IBC have progressed substantially since the building code that was in effect at the time of original construction, making any attempt to comply with the current IBC requirements difficult. Work Area Compliance MethodThe work area compliance method is the most-commonly used compliance method in the IEBC and generally the most flexible from a technical requirement standpoint. This method applies varying requirements to the work area in the building based on the classification of work that is being performed. When the work area compliance method is used, the scope of work must comply with one or more of the applicable chapters:
For any building alteration, the requirements of Chapter 7 would apply. If the alteration includes “the addition or elimination of any door or window, the reconfiguration or extension of any system, or the installation of any additional equipment,” (IEBC Section 603.1), the requirements of Chapter 8 would also apply for a Level 2 alteration. If the work area exceeds 50% of the building, the requirements of Chapter 9 would also apply for Level 3 alteration. Changes of occupancy and additions using the work area compliance method must comply with Chapters 10 and 11, respectively. Finally, if you have a historic building, be sure to reference IEBC Chapter 12 first, as it modifies several the requirements found in Chapters 7-11. Performance Compliance MethodThe performance compliance method involves the evaluation of a variety of building systems and components (including height/area, compartmentation, vertical openings, means of egress, and fire protection systems). These systems are each assigned a score based on the evaluation criteria found in IEBC Chapter 13. These scores are then added to determine a total building score. If the score is high enough for the occupancy classifications involved, the work is deemed to be in compliance with the IEBC. The performance compliance method is a good option when one aspect of a proposed scope of work cannot conform to the other compliance methods, but the remainder of the building is generally compliant. For example, if an existing building work areas has excessive dead corridor lengths, compliance with the prescriptive compliance method or work area compliance method may be impossible. But the performance compliance method may be a viable option, assuming the building scores well in the other assessment areas. IBC ComplianceAs described above in Scenario 1, compliance with the requirements of the IBC is only required when specifically referenced by the IEBC (or potentially in the IFC and IPMC). That said, if your work complies with the requirements of the current edition of the IBC adopted in your jurisdiction, this will inherently satisfy the requirements of the IEBC prescriptive compliance method. What about NFPA 101?NFPA 101 Chapter 43 applies to any building rehabilitation work, including repairs, renovations, modifications, reconstruction, changes of use/occupancy and additions. Any of these actions would trigger a requirement to comply with NFPA 101 Chapter 43, which then brings in requirements to comply with other portions of NFPA 101, depending on the scope of work. Generally, NFPA 101 Chapter 43 requires compliance with all requirements found in the applicable existing occupancy chapter (Chapters 13,15,17,19, etc.) plus some additional requirements that vary based on the type of work being performed. IFC ComplianceAs described in Scenario 1, application of the IFC is divided into two categories:
IFC Construction and Design RequirementsPer IFC Section 102.1, the construction and design provisions of the IFC “apply to:
Just as in Scenario 1, Items 3 and 4 would also apply to Scenario 2. Additionally, Item 1 would also apply to the work being performed in the building (since it is creating a new condition). Therefore, any requirement found in the IFC that is applicable to a system or component within the work being performed is applicable. This means you’ll need to review the IFC chapters that are relevant to the given system or component of your building under consideration to determine if there are any applicable requirements. IFC Administrative, Operational and Maintenance ProvisionsPer IFC Section 102.2, the administrative, operational and maintenance provisions of the IFC “apply to:
What about NFPA 1There are requirements throughout NFPA 1 that would apply to Scenario 2, so again you’ll need review the chapters that are relevant to the given system or component of your building that will be changed and find the requirements for existing buildings within those chapters. ConclusionThe phrase “meeting code” is used frequently in the A/E/C world but depending on the nature of your building and the work being performed, it can mean many different things!
For an existing building, you likely fall under one of these two scenarios:
Scenario 1 typically requires compliance only with certain portions of the IFC. Scenario 2 requires compliance with the IEBC and the IFC. If you are in a jurisdiction enforcing NFPA 1 and 101, there are also requirements from these codes that apply to both scenarios. The IBC offers 3 approaches to mixed occupancy buildings: accessory, nonseparated and separated. Any building with two or more occupancy types must choose one or more of these approaches for compliance. In this post, we will cover all three of these approaches and the specific requirements related to each.  Many urban buildings are mixed occupancy buildings and use one of these described approaches. Nonseparated Mixed OccupancyIn a nonseparated occupancy approach, there is no requirement for a fire-rated separation between adjacent occupancies. However, the key requirement in a nonseparated occupancy approach is that the most restrictive requirements for the allowable height, area and number of stories, as well as the most restrictive fire protection requirements must be applied throughout the entire building. For example if your building has two occupancy types and one of them requires a voice fire alarm system, a nonseparated occupancy approach would mean that you need to provide a voice fire alarm system throughout the building. If your building falls within the allowable height and area for the occupancy types involved and you can meet the fire protection requirements of the most restrictive occupancy, a nonseparated mixed occupancy approach is the easiest from a design standpoint because there is no additional requirements for rated separations. The general approach for code compliance in a non separated mixed occupancy building is: 1. Determine the maximum allowable height, area and number of stories for each occupancy involved and verify that your building meets the most restrictive requirements. 2. Determine the fire protection requirements from IBC Chapter 9 for each occupancy involved and apply the most restrictive requirements throughout the building. If the building is a high-rise, the requiremetns of Section 403 would also apply throughout. 3. Apply all other code requirements, such as means of egress, to each individual occupancy classification individually for that portion of the building. Note that even if you are taking a nonseparated occupancy approach there are specific requirements for buildings containing Groups H, I and R for a rated separation between those occupancies and adjacent building spaces you can review those requirements in IBC Chapter 4. Separated Mixed OccupancyThe separated mixed occupancy approach is typically provided when the non-separated approach is not an option. With a separated mixed occupancy approach, a fire-rated separation is typically provided between each occupancy type. IBC Table 508.4 is referenced for the specific rating requirement, though a rated separation may not be required between occupancies of a similar hazard level. The allowable height and number of stories is applied for each individual occupancy type. For example, if your construction type limits a Group A occupancy to 4 stories, your building could be taller as long as the Group A occupancy is not located above the fourth story. The allowable area is based on the sum of the ratios of the actual floor area for each occupancy divided by the allowable floor area of that occupancy. The sum of these ratios cannot exceed one for any given story. Requirements for egress and fire protection systems are applied invidivualy to each separated occupancy in the building. The general approach for code compliance in a separated mixed occupancy building is:
Accessory OccupancyThe final option is an accessory occupancy approach. This method is applicable where there is a small portion of a building or space that is subsidiary to the main occupancy. When that smaller space is 10% or less of the total area of a story, an accessory occupancy approach can be used. There is no required separation between the accessory and main occupancy, and the building height, area and number of stories are based on the main occupancy, not the accessory occupancy. If the building contains a Group H, I or R occupancy, those separation requirements found in Chapter 4 would still apply. Within the accessory occupancy, other code requirements such as egress and fire protection systems are based on the accessory occupancy classification, not the main occupancy. This is crucial point that confuses many people. Essentially, the accessory occupancy designation allows you to ignore the height, area and number of stories requirements for the accessory occupancy, but all of the other code requirements for the accessory occupancy still apply. For example, a large conference room located within an office building could be considered an accessory occupancy, so the limitations for height, area and number of stories for Group A-3 occupancies would not apply. But all of the other code requirements for Group A-3, including means of egress and fire protection requirements would still apply! Bonus: Fire WallsOne final option - if you are able to separate multiple occupancies using a fire wall, you create two separate buildings from a code application standpoint and you can consider each building indvidually. A fire wall is the most robust separation option available though, so its likely to be the most disruptive from a design standpoint. ConclusionIn summary, there are three approaches to mixed occupancy buildings: non separated, separated and accessory. All buildings with multiple occupancies must use one or more of these approaches. If your building contains three mor more occupancy types, it's possible to use a combination of the approaches, such as designating an accessory occupancy and then taking a nonseparated approach for the remaining occupancies.
If you have designed a building of Type II, III, IV or V construction, you probably considered the allowable building area, which depends on the construction type, occupancy classifications, presence of fire sprinkler systems, and a few other criteria.
One common way to increase the allowable area for a building is to use a frontage increase. The frontage increase provision in the IBC, found in Section 506.3, recognizes the safety benefits of having open space directly adjacent to a building. When a fire department or other emergency responders arrive to a site, there is an increased level of effectiveness when those personnel can access a large portion of the building exterior. 
A public way, such as a street that is at least 20 feet wide, counts towards the frontage increase.
Using Frontage to Increase Allowable Building Area
There is no requirement for a building to use the frontage increase provisions of IBC Section 506.3, but when used, the following requirements apply:
Performing the Frontage Calculation
The frontage calculation can be performed by hand, but I recommend the building frontage calculator. If you want to do the calculation on your own, here are the steps. Note that this method is valid through the 2018 IBC. Starting in 2021, the method has changed, which I will cover in a future update.
1. Determine the weighted average of the width of open space (W). This value, W, is determined by the following equation:
W = (L1 x W1 + L2 x W2...)/F
Where: Ln and Wn are the length of wall segment and width of open space adjacent to that wall segment. Remember that W has to be at least 20 feet. If the width of the public way or open space is greater than 30 feet, you are required to use a maximum value of 30 feet for the calculation. F is total building perimeter fronting a public way or open space with a width of 20 feet or more.
2. Determine the total building perimeter, P.
3. Solve IBC Equation 5-5 to determine the frontage increase factor.
If = [F/P - 0.25] W/30
The frontage increase factor can then be used with IBC Equations 5-2 or 5-3 to determine the allowable area the building. In these equations, the frontage increase factor is multipled by the "NS" allowable area value from IBC Chapter 5. Notice that with Equation 5-5, the maximum possible frontage increase factor is 0.75. In order to achieve this maximum value, the entire building perimeter has to front an open space or public way with width of 30 feet or more. If the width at any point is less than 30 feet, or if a portion of the building perimeter does not have any frontage, the frontage increase factor will be reduced. You can also directly input the frontage increase factor into the allowable area calculators below: Conclusion
Using the frontage increase provisions of IBC 506.3 is a common way to increase the allowable area of a building. There is no requirement to use these provisions, but when you do, the requirement described above do apply.
When working with architects, I frequently see code summary sheets with a frontage calculation for Type I buildings that have an unlimited allowable area. Since there is no requirement to take a frontage increase, I typically remind architects they don’t need to perform the frontage calculations if the building already has an unlimited allowable area. This saves time and also prevents possible permit review comments on a code provision that wasn’t needed in the first place. |
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