3 Critical Elements for Commercial Office to Residential Conversions

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Aric Aumond, P.E.


March 8, 2024

With office vacancies dramatically on the rise, building owners are looking for new ways to utilize office space. One answer is to convert commercial offices into residential living areas. But before you make the move, consider these three elements.

The pandemic has changed many aspects of our daily lives, including how we work. Before, many employees were expected to be in the office five days a week. Now, it’s common for employees to work from home at least part of the time. This change in work behavior has led to office vacancies throughout the United States. In fact, the overall U.S. office vacancy rate is expected to reach 19.7% by the end of 2024.

Meanwhile, the need for affordable housing continues to increase. At the end of 2020, the market was short 3.8 million housing units, and those numbers were expected to rise due to the impact of the pandemic.

To meet the needs of office building owners and residents, the Biden-Harris Administration released guidance on the federal resources available for commercial to residential conversions. The goal is to help building owners convert their office spaces into residential living areas so that the building owners can generate income and residents have a place to live.

But before you start repurposing your office building, there are a few critical factors to consider. Let’s explore them now.

Commercial Office to Residential Conversion: 3 Elements to Consider

1. Building Size: Allowable Height, Number of Stories & Floor Area

Before undertaking a commercial office to residential conversion project, carefully consider the building’s height, number of stories and floor area. Each of these factors is limited within the building code based on the specific hazards associated with the building’s occupancy classification, materials of construction and whether fire sprinkler protection is provided. When the occupancy classification changes, so do the maximum allowable values for each of these categories. Generally, residential requirements are more stringent than business, so if a building was built to the maximum allowable values for a business occupancy, then a residential conversion may not be feasible without significant modifications, such as increasing construction type.  

There are various building codes and regulations governing these parameters to ensure life safety is maintained within the converted building. Each jurisdiction may have amended the requirements, so it is important to consult with a professional familiar with the locally adopted standards.

Each of the limiting factors (height, stories and area) is presented in the building code through tables. According to the International Building Code (IBC) Section 504.3, the maximum height, in feet, of a building can’t exceed the limits specified in Table 504.3.

IBC Table 504.3 Allowable Building Height in Feet Above Grade Plane

Looking at the table, it’s important to note that under Occupancy Classification, “B” stands for “Business,” and “R” stands for “Residential.” Then, there are five categories under Type of Construction you should know:

  • Type I and Type II: The building elements are of noncombustible materials.
  • Type III: The exterior walls are of noncombustible materials, and the interior building elements are of any material permitted by IBC Section 601.
  • Type IV: The building elements are mass timber or noncombustible materials and have fire-resistance ratings in accordance with IBC Table 601.
  • Type V: The structural elements, exterior walls and interior walls are of any materials permitted by IBC Section 601.

The type A vs B construction represents an additional fire-resistance rating of primary structural elements, which is described in Table 601 of IBC. 

In addition, there are several sprinkler options to note:

  • NS: Buildings with no automatic sprinkler systems
  • S13D: Buildings equipped with an automatic sprinkler system installed according to NFPA 13D
  • S13R: Buildings equipped with an automatic sprinkler system installed according to NFPA 13R
  • S: Buildings equipped with an automatic sprinkler system installed according to NFPA 13

The maximum allowable number of stories is determined by Table 504.4 and the maximum allowable area is determined by Table 506.2 of the IBC. When you’re considering a commercial office to residential conversion, understanding the parameters in each table is critical because these limitations help assess the feasibility of the conversion and guide the planning process.

How to Use Table 504.4 When Planning a Conversion

Let’s say your existing office building is 6 stories, has a sprinkler system and is constructed with Type II-A materials. According to Table 504.4, your maximum allowable number of stories is six (6), and therefore this was a code-allowed building. 

However, you plan to convert to a residential apartment building (R-2). According to Table 504.4, your maximum allowable number of stories is only five (5). Therefore, the residential R-2 occupancy would not be feasible in this building without significant corrective actions. Alternatively, an alternative means methods request (AMMR) and performance-based design could be considered to allow residential use in this existing building. 

Therefore, you must consider whether it’s worth the cost of renovating your commercial building to meet those requirements.

2. Allowable Travel Distance to Exit

Another element to consider is the maximum allowable travel distance to an exit. For example, IBC Section 1017.2 says the exit travel distance can’t exceed the values provided in Table 1017.2, which is shared below for reference.

IBC Table 1017.2 Exit Access Travel Distance

Again, “B” stands for “Business,” and “R” stands for “Residential.” So, if your office building has a sprinkler system, the allowable travel distance to exit is 300 feet. However, a residential building with a sprinkler system only has an allowable travel distance of 250 feet. If the maximum travel distance was originally designed to be just under the maximum allowed for a business occupancy (say 275 feet, for example), then you would exceed the maximum allowable distance for a residential occupancy and not be in compliance with the building code. 

There are various options to address travel distance deficiencies, including a performance-based design.

Option 1: Add an Exit Stair

Adding an exit stair to a residential building can be expensive primarily due to the structural modifications required. Structural changes that involve cutting through walls or creating new openings in floors are labor-intensive and costly. Planning the location of a stair and installation within an existing building is challenging and usually not a feasible option. In addition, the loss of leasable square footage could impact the resale value or decrease projected rents.

Option 2: Add an Exit Passageway

Another option is to add an exit passageway, which is a designated, protected pathway within a building that provides a safe route for occupants to evacuate during emergencies, such as fires. It typically is used to extend an existing exit to be within the allowable travel distance. It’s a horizontal exit vs a vertical exit, such as a protected stair enclosure. An exit passageway may be appropriate when the deficiency is less than 10 feet. This option can be expensive because you must add an exit passageway to every floor. In addition, the loss in leasable area would likely be greater with this solution than the previous. 

Option 3: A Performance-Based Approach

In certain situations, a performance-based approach can be utilized to leverage excess travel distances slightly above the code maximums. We have utilized fire and egress modeling to justify these conditions successfully, oftentimes with an additional method of fire protection and life safety required (such as additional smoke detection or a higher level of sprinkler protection).

The Importance of Corridor Fire-Resistance Ratings

While we’re on the topic of allowable travel distance to an exit, another factor to consider is the fire-resistance rating for your corridors, which is the level of fire protection that a corridor or pathway within a building provides against the spread of fire and smoke.

This rating is typically expressed in terms of time, such as 30 minutes, 60 minutes or 90 minutes. It indicates the duration for which the corridor can withstand exposure to fire before it compromises the safety of occupants or allows fire and smoke to spread to other parts of the building. Corridors with higher fire-resistance ratings offer increased protection and can allow more time for occupants to evacuate the building during a fire emergency safely.

IBC Table 1020.2 specifies the required corridor fire-resistance rating:

IBC Table 1020.2 Corridor Fire-Resistance Rating

In office buildings without sprinkler systems, the fire resistance rating for corridors and pathways is 0 hours, meaning they are not required to provide any listed protection against fire spread. However, in residential buildings equipped with sprinkler systems, these corridors and pathways must have a minimum fire-resistance rating of 30 minutes and possibly 60 minutes, depending on the type of sprinkler system installed. This difference is crucial for ensuring the safety of occupants during a fire emergency.

When converting a commercial office building into a residential one, it's essential to assess the existing corridors and pathways. This consideration becomes especially relevant if the existing corridor walls will be maintained in the conversion process. Modifications, such as providing additional layers of gypsum wallboard or extending walls above the ceiling to the deck above, may be necessary to meet the 30- or 60-minute fire resistance rating required for residential occupancy. 

3. Sprinkler Protection & Fire Alarm Systems

The need for sprinkler protection and fire alarm systems in a building depends on various factors, such as the occupant load, max fire area size, construction type and various other construction factors like building height and number of stories. 

By default, sprinkler protection may not be required for an office building, but all residential occupancies that fall under the IBC are mandated to have fire sprinklers installed (keep in mind that local code amendments may deviate from the base IBC). Therefore, if your office building doesn’t have a sprinkler already, you may need to install one for the residential conversion.

Architectural renovations of the space, proposed as part of the conversation, will impact existing systems necessitating some level of system redesign ranging from simple sprinkler head relocation to fire pump replacement. Residential sprinklers are specially designed sprinkler heads that offer extended coverage per individual sprinkler. These are often desirable in residential occupancies for coordination purposes with reflected ceiling plans. However, they can strain the capacity of existing fire pumps due to higher demand, potentially necessitating upgrades, sometimes resulting in significant costs.

In addition, a change in building use to residential requires extensive redesigning of the fire alarm system, including the addition of devices and upgrades to power supplies. It may be necessary to upgrade the panel to accommodate additional devices or, in some cases, a complete system replacement with a new modern system. Keep this in mind before you start your conversion.

Bonus Elements to Consider

In addition to the fire protection elements outlined above, it’s also important to think about these three factors for your conversion:

  1. HVAC needs
  2. Electrical needs
  3. Plumbing needs

1. HVAC Needs

Commercial offices usually have a large HVAC system for the whole building, while residential buildings need separate systems and control for each unit. 

Also, residential HVAC systems are smaller than those in offices, which can cause humidity problems if they're too big. Adding more exhaust fans and adjusting airflow can help with this, but that’s an additional cost.

2. Electrical Needs

Considering electrical needs is crucial when converting a commercial office space into residential units due to the significant differences in electricity usage patterns and requirements between the two types of buildings.

Residential units typically demand higher electrical loads for kitchen appliances compared to the predominantly electronic equipment found in office settings. Additionally, while office buildings may have sufficient electrical capacity for their operations, adjustments such as adding subpanels to accommodate the increased demand in residential units are often necessary. 

It’s also integral to consider compliance with building codes, such as ensuring residents' access to circuit breakers or fuses.

3. Plumbing Needs

While office buildings typically have centralized plumbing systems designed for commercial purposes, residential units require distributed plumbing to accommodate individual bathrooms and kitchens in each unit. The conversion process entails assessing the size of pipes, ensuring compliance with local codes, and potentially upgrading the plumbing infrastructure to meet residential demands.

Challenges may arise in adapting the sewer system, especially on upper floors, where gravity plays a crucial role in proper drainage. Addressing plumbing needs during the conversion ensures functional and efficient water and sewer systems, essential for the comfort and convenience of the residential occupants.


The conversion of commercial office buildings into residential spaces presents a promising solution to address both the surplus of vacant office buildings and the growing demand for affordable housing. However, this transition requires careful consideration of three critical factors: the building size (allowable height, number of stories, and floor area); travel distance to exits; and impact on existing fire sprinkler and fire alarm systems.

By strategically addressing these factors, you can successfully repurpose your property to meet the evolving needs of communities while maximizing their investment potential in the real estate market.

Need help with your commercial to residential conversion? Partner with Performance Based Fire for expert code consulting, fire and life safety narrative services and fire and life safety system design. Contact us now to get started.