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Adaptive Reuse: Office and Housing that Begin as Parking Structures

As we continue contemplating the impact of new technology such as driverless cars on the parking industry, designing parking facilities for adaptive reuse is a popular topic of discussion. Previously, we examined this topic from the perspective of converting a parking structure to non-vehicular uses. However, what if we took a different design approach?

By envisioning the future purpose of the building first and then determining a design approach that supports conversion, owners can make an initial investment into the parking structure as well as an early investment into a future project. If planned properly, much of the infrastructure for the eventual occupied use can be designed into the parking structure, so that the conversion to an occupied use in the future would involve little more than constructing the exterior façade and building out the tenant improvements.

Design for Adaptive Reuse

What design strategies need to be employed to make future conversion of a parking garage to an alternative use more feasible? The structural and façade designs of occupied uses are very different from what is typically incorporated into parking facilities, as are floor heights, pedestrian circulation, etc. Therefore, the following best practices should be considered with the intended future use in mind.

Image for Adaptive Reuse: Office and Housing that Begin as Parking Structures Design for ground-level retail with parking above

Structural Design Considerations

While it seems counterintuitive, the structural load on a building for parking cars is about half the load needed to support an occupied space such as an office or housing. Therefore the effective design load of a parking structure is relatively low compared to other uses. Identifying and incorporating the future loading needs will make adaptation much easier.

The structural floor framing would also need to be considered. Parking structures typically use either a short or long span system, which have advantages and disadvantages depending on the intended use.

The most efficient system for parking cars is a long span system, where beams span the entire parking bay. This avoids the need for columns between parking stalls, but the floors can sometimes be a little bouncy and the support beams typically extend 30” or so below the underside of the deck above. A long span system can park more cars in the same footprint, and the lack of columns can improve the user experience. In order to accommodate a future alternative use for ducts, etc., a long span system would require a higher floor-to-floor height.

A short span system has additional columns, but can provide for a stiffer floor, which is desirable for the future office or residential use. As a bonus, there are typically no beams to contend with during the retrofit, which allows the greatest flexibility for running ducts, plumbing and conduit, while reducing the overall height of the building. The short span system is generally cheaper for the same footprint as a long span system, but the additional columns reduce the number of cars you can park and users are required to park in between columns.

Whatever structural framing is selected for the design, understanding what challenges and opportunities it poses for future conversion is an important consideration. For converting a parking structure to office or residential, the short span system is generally the best choice to blend parking requirements with future uses such as office or residential.

Image for Adaptive Reuse: Office and Housing that Begin as Parking Structures Cutaway view showing ramp configuration in center of building

Design for Daylight

Most traditional parking garages have large, deep floor plates, which can cause the central portions of the structure to feel dark and therefore less desirable for human occupancy. However, one way to mitigate this involves careful consideration of ramping configurations. Ramps, while inherent to the design of typical parking garages, are not conducive to occupied uses and should be designed with removal in mind. By locating the ramps in the center bay of the garage and using modular components that can be disassembled and removed in the future, the center of the building can be transformed into an atrium. This would provide natural light and ventilation to the inner portions of the converted building, and perhaps a courtyard amenity for building occupants.

Image for Adaptive Reuse: Office and Housing that Begin as Parking Structures Cutaway view with ramps removed to provide a light-filled atrium

Pedestrian Circulation

Most occupied buildings place stairs and elevators in the center of the building, to open up as much of the perimeter as possible to bring daylight into the space. However, in most garages, the stairs and elevators are located in the corners of the building, making use of space that cannot be used for parking. The number of and width of egress pathways, stairs and elevators must also account for a future use.

Façade Design

Unlike occupied spaces, above ground parking garages typically rely on natural ventilation. Therefore, to enclose the building for an alternative use, the façade should be designed for flexibility.

Exterior cladding such as metal mesh, louvered panels or perforated metal panels is often added to a parking garage to obscure view of the cars while still maintaining openness. Since this will need to be replaced with walls and windows, the attachment of the cladding should be designed for easy removal. Likewise, precast or cable rails are desirable guardrail systems, as they can be easily removed in the future and provide flexibility to incorporate walk-out balconies.

Image for Adaptive Reuse: Office and Housing that Begin as Parking Structures Ground-floor retail, one level of parking, with offices above

Today’s Cost Versus A Longer-Term Return on Investment

In addition to looking at adaptive reuse from a different angle, we also examined the cost of such an endeavor from an alternative perspective. When viewed in the short term, the cost of designing for later adaptive reuse can give you pause. However, when you take a more holistic, long-term look at the return on investment or ROI, a compelling case can be made for the right location.

The cost of adapting a parking facility to an alternative use can cover a wide spectrum. Both upfront costs and long-range savings should be considered when evaluating potential return on investment. Site location, value, demand and density are key factors in this decision.

At the lowest end of the spectrum, designing the ground level for future conversion can offer minimal cost impacts while still providing flexibility. Designing flexibility into upper levels requires greater upfront investment, while fully designing an entire structure for adaptive reuse can increase cost by 40% or more. However, when viewed as an investment in the full life of the development, it can potentially provide a more cost effective way to reap development benefits down the road by paying for a future project in today’s dollars.

In addition to the long-term cost benefits, building for later adaptive reuse also provides a more sustainable development approach in the event demand for a parking facility decreases in the future. Converting an existing parking structure to an alternative use is a much more sustainable approach than demolishing it and building something new in its place.

By looking at designing for later adaptive reuse from different angles, owners have more options or flexibility to consider when meeting the long term needs of their investments than ever before. By taking a number of best practices into consideration during the initial design, many of the challenges conversion poses can be overcome. For owners willing to make the investment, “future proofing” parking can provide a long-term, cost-efficient and sustainable solution that keeps tomorrow in mind.

About the Author

As an Associate Principal, Anita leverages over 15 years of experience in the engineering of parking structures to coordinate with clients, consultants and contractors throughout all design and construction phases of the project. Anita has extensive training in structural engineering, including award-winning projects such as the San Jose State University South Campus Multi-Level Parking Structure & Sports Field Facility.

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