Parking Garages, A Contrarian Perspective

By William F. Kavanagh, AIA 

Recently, there have been scores of articles advocating for future-proofing parking garages — designing them to be easily converted to another use when the need for parking significantly declines or is perhaps eliminated all together with the universal adoption of remote work, internet shopping delivery, ride sharing services, and autonomous vehicles. Many claim that adaptive reuse of a garage into residential or office space would be cost effective and sustainable. 

I’m here to challenge those assumptions about the decline of parking demand, and dig into the technical challenges and cost implications of designing a free standing garage with an eye towards adaptive reuse.  

ARE CARS GOING AWAY? 

The premise used to justify future-proofing garages is that the need for parking will decrease significantly. In my opinion, that is a very big “If.” Autonomous vehicles would need to drive around continuously with and without passengers at all times of day and night to achieve a significant decrease in parking demand. During off-peak demand times, autonomous vehicles will likely park somewhere to reduce wear and tear on the roads and themselves, and to conserve energy. They will also need to park to recharge or refuel.  

Some individuals might also prefer private ownership of their autonomous vehicles in lieu of sharing. Their vehicle will chauffeur them between various destinations and park when not in use, waiting to be summoned for its next trip.  

“In the future, parking garages as we know them may become obsolete. With driverless cars reducing the need to park, parking spaces will need to be converted for better uses.” — “Future Proofing Garages With Smart Parking”, Shubhankar Gautam, July 1, 2019; blog, getmyparking.com 

“The trend is for fewer cars on the road. Fewer cars means a  
reduced need for parking.”— “Three Trends in Parking Garage Design in Kansas City”, McCownGordon Construction, September 26, 2022 

The argument that a reduction in parking demand is premature isbolstered by the September 2021 Parking Today article, “Planners Disregard the Facts,” by John Van Horn. Here are some quotes from Dale Denda, Research Director of the Parking Market Research Company: 

“…the market research in the automotive supply chain sector shows that by 2025, there will be five million MORE cars on the road in the U.S. than there are today [2021].” 

“We too often forget that off-street parking REMOVES vehicles from the roads, addressing the key problem for the transportation sector that is congestion.” 

“The numbers to justify projections of a reduction in driving/parking demand simply aren’t there.” 

“…Less than 5 percent of households today in the United States don’t own a vehicle — the needle hasn’t moved on that datapoint in decades.” 

 Finally, a huge impediment to reducing and/or eliminating the inventory of existing parking spaces will be the zoning requirements in every municipality across the nation. It would require a considerable amount of time and effort to advocate and re-write local regulations.   

FUTURE-PROOFING PARKING GARAGES ISN’T SO EASY 

The articles on future-proofing garages often do not distinguish between different types of garages. Garages can be underground, podiums beneath other occupancies, and/or free standing. It is important to understand what type is being discussed.  

An underground garage is more limited in its adaptable reuse potential due to its lack of access to natural light. Some have suggested storage, data centers and movie theaters as potential reuses, but underground garages are less likely candidates for conversion than podium and free-standing garages.  

A podium garage beneath an office or residential tower is a good candidate for repurposing. The structural layout is most likely a function of the office and/or residential grids and core locations. It is also more likely to have shorter spans and more columns compared to a stand-alone garage. 

A stand-alone garage is the most specialized, single-use, optimized, efficient, cost-effective way to provide structured parking. The design features incorporated to facilitate an adaptive reuse in the future will compromise its efficiency and cost effectiveness. There is a premium for this future flexibility.  

The following are potential design features that would facilitate a future adaptive reuse of a garage into an office or residential occupancy: 

• More area of flat floors a.k.a. no ramps with parking 

• Shorter, steeper speed ramps without parking that will be removed 

• Taller floor-to-floor heights to accommodate other uses, especially on the ground floor 

• Elevator and stair locations in the middle of the garage instead of at the corners 

• Atrium or lightwell in the middle of the garage, providing access to natural light for adaptive reuse 

• A short-span structural system instead of a long-span system such as precast concrete  

• Higher structural loading compatible with the future reuse occupancy type  

The most efficient structural system for a garage is a long-span system such as precast double tees. This way, there are no columns needed between the parking spaces. However, these systems are not ideal for an adaptive reuse with occupied floors. Their long spans deflect and bounce too much for human occupation.  

Garages have lesser structural loading requirements compared to other occupancies. The garages will need to be designed for the additional loading demand required for future uses. Therefore, if designing for a future adaptive reuse, short-span systems are likely. Short span systems have additional columns between spaces at the ends of the stalls. They can be designed for greater loading, and less deflection and movement.  

Some of the upfront cost premiums for future proofing include: 

Greater area per parking space (loss of efficiency) resulting from the following: 

• The additional columns of a short-span system 

• Speed ramps without parking 

• Internal light wells 

• Interior elevator and stair towers 

• A more expensive structure with higher loading 

• Less durable structural system (conventionally reinforced versus precast) requiring additional durability provisions (ex. traffic membrane) 

THE COST OF FUTURE-PROOFING 

“Future proofing implies a higher cost … some estimates can be up to 1/3 of the total construction cost.” — Wayfinding Blog, “Repurposing and future-proofing car parks,” February 17, 2020 

“Fully designing an entire structure for adaptive reuse can increase cost by 40 percent or more.” — “Adaptive Reuse: Short Term ROI or Long Term Investment,” Jess McInerney & Matt Davis for Parking & Mobility Magazine, August 2021 

“Some responses can be easily incorporated with minimal cost but there are those that can increase project costs manyfold, sometimes beyond 50 percent of typical expenses for self-parking projects.” — “Future-Proofing Parking Buildings,” Fernando J. Sanchez, Parking & Mobility Magazine, October 2019 

Another challenge for the conversion of a garage that is rarely discussed is how to eliminate the secondary drainage slopes in order to provide flat floors for the new use. It is a building code requirement and recommended practice to slope floors to drains. These secondary drainage slopes are typically in the 1.5 to 2 percent range. Providing a substantial topping slab of varying thickness on such large areas to achieve a level floor will be a significant cost and effort at the time of conversion. 

Designing a free-standing garage with flexibility for a future adaptive reuse for human occupancy will increase the upfront costs of the garage. The case study at the end of this article shows a 54 percent premium for future-proofing the structure of a free- standing garage. 

TIME AND SUSTAINABILITY 

Other important components of the cost equation include time and sustainability. The old adage is true: “Time is Money.” Understanding the time and effort required for converting a future proofed garage compared to its demolition and replacement altogether is not clear cut, even though other writers have presented the idea of converting free standing garages as efficient. 

“Tearing down a building and building a new one takes more time, money and resources than adapting a building for another use.” — “Designing Garages so They can Easily Become Housing!” Modelur.com, Sonja Jerse, August 14, 2018 

“It can be converted into another use in the fraction of the time and cost that would be required to build something from scratch.” — “Designing parking garages so they can be easily become housing,” Megan Ridgeway, July 23, 2018, fastcompany.com 

“It’s also cost-efficient in the long term, as it costs far less to re-purpose than it does to demolish and start from scratch.” — “Parking in a Changing CRE Marketplace: Adapting & Futureproofing,” September 25, 2019 

Although not within the scope of this article, the implications for minimizing a building’s carbon footprint and environmental impact should also be considered. By reusing and repurposing the structure, we reduce future waste and additional materials needed for replacement. Is it a more sustainable approach to build an optimal garage that is replaced by an optimal residential building instead of a sub-optimal garage that can be converted into a sub-optimal residential building in the future? At what point does it become economically untenable?  

A LOOK AT THE NUMBERS 

Whether or not to reuse a garage by converting it into another building type is all about the garage’s superstructure. Is it better to build twice with a garage first followed by a new residential building or to build once with a convertible garage design that can be repurposed? Which of the following two scenarios costs less in Metro Philadelphia? 

Option 1: Build a new, free standing, single-purpose, efficient, economical, long-span, precast garage that is to be demolished in 20 years, plus the cost of the new residential building superstructure only.   

Option 1: Long Span, Precast Garage/Demo Garage/New Residential Building Structure Only 

5 1/2 levels; 610 spaces; 187,185 SF; 306.9 SF/space; Typ. Tier 36,095 sf 

* average rate of inflation from 1914-2024 is 3.3% 

**area of option 2 garage 233,524sf x 4/5 = 186,819 sf since top level becomes roof at conversion 

Option 2: Short Span, Conventionally Reinforced Concrete Garage/Reuse Structure for Residential Building  

5 levels; 606 spaces; 233,524 SF; 385.4 SF/space; Typ. Tier 47,532 sf 

* short span, field labor, more columns, higher loading, drainage slopes, admixtures 

** traffic membrane required to match precast durability of Option 1 

*** traffic membrane $8/SF @ 3.5% x 10 yrs = $11.28/SF 

**** demo slab on grade, lighting, floor drains & risers, standpipe, signage, misc. 

***** $15/SF in 2025 @ 3.5% for 20 years = $29.85/sf; 3 floors only, not ground or top tier 

Option 2: Build a new, free standing, short span, conventional reinforced structure that can be converted into a residential building in 20 years. For the point of comparison, assume this only includes select demolition and concrete toppings on the sloped floors to get the garage structure ready for the residential conversion 

The first option has a first construction cost of $21,350,000 in 2025. The second option has a first construction cost of $32,907,636, which is an upfront premium of $11,557,636 (+54%) for the same number of parking spaces and the future flexibility for potential adaptive reuse into a residential building.  

Fast forward 20 years and assume it’s time to change the parking garage into a residential building. The first option involves demolition of the garage and construction of a new residential building superstructure; Option 2 requires selective demolition of parts of the existing future-proofed garage structure to prepare it for the residential conversion. The total cost for Option 1 appears to be approximately $51.5 million. The total cost for Option 2 appears to be approximately $42.5 million.    

The difference in the cost of the two options appears to be $9 million in favor of Option 2. But what about the Time Value of Money and the Upfront Cost Premium? The upfront cost of Option 2 is $11.5 million more than Option 1. The $11.5 million saved in upfront costs of Option 1 could be invested over the 20 year period before demolition and replacement. $11.5 million invested for 20 years with a 3.5 percent average rate of return will become approximately $23 million. The same amount for 20 years with a return of 9.67 percent (the average for the S&P 500 index over the last 30 years) could be approximately $73 million! Both of these amounts are well in excess of the potential $9 million in savings for Option 2. The considerable upfront cost savings and investment return of Option 1 can be put to funding the future residential building and investment in sustainable initiatives for any offsets. 

While predicting the future can be challenging, it is clear that the premium for future-proofing a stand-alone garage is not an obvious and clear cut decision. The decision with less risk, based on construction costs and the time value of money, would be to build the single use, ideal, efficient, and economical free standing-garage rather than a future-proofed one. ■ 

William F. Kavanagh, AIA is an associate principal and Parking Consultant of Distinction at IMEG Consultants Corp. He is an architect with 22-plus years of experience specializing in the design of parking garages, including underground, podiums in mixed-use buildings, and free standing models. He has designed over 500 parking garages. 

CAPTIONS: 

Long Span, Precast Structural System 

PHOTO: WILLIAM F. KAVANAGH 

Short Span, Structural System 

PHOTO: WILLIAM F. KAVANAGH 

Option one, left: Long Span, Precast Garage; Option two, right: Short Span, Future-Proofed Garage 

PHOTO: WILLIAM F. KAVANAGH