Converting a rooftop pedestrian plaza into functional parking requires more than laying down pavement. Adding a vehicle ramp to an existing parking deck involves structural analysis, selective demolition, shoring, column reinforcement, concrete placement, and careful sequencing to keep the facility operational throughout construction. The One E Pratt Street Garage in Baltimore is a real example. The Bartley Corporation transformed a rooftop terrace into 150 new parking spaces with a vehicle ramp connecting the top deck to the level below. Understanding the construction methods behind this work is valuable for any contractor evaluating similar opportunities. For a broader understanding of parking facility design, see our article on Parking Space Types and Multi Level Car Parking systems.
Planning and Structural Assessment Before Adding a Ramp
Before any demolition or concrete work begins, a thorough structural assessment must determine whether the existing deck can support the new ramp and additional vehicle loads. In the Baltimore project, the original garage was designed with the top level serving as an atrium patio for pedestrians, not vehicles. Converting this space meant the structural team had to evaluate every load path from the new ramp down to the foundations.
Key Structural Factors to Evaluate
- Existing slab capacity: The original floor system, often built with precast Double T beams as seen in the Baltimore garage, may have been designed for lighter live loads. Adding vehicle traffic requires confirming slab capacity or planning reinforcement.
- Column and beam load paths: The new ramp introduces concentrated loads at support points. Columns near the ramp opening may need strengthening, as Bartley discovered when engineers identified several columns requiring reinforcement before construction could proceed.
- Lateral stability: Cutting an opening through the deck for a ramp changes the lateral load distribution of the structure. New shear walls or moment frames may be necessary to maintain stability during seismic or wind events.
- Waterproofing requirements: Any new concrete topping over an occupied lower level must include a reliable waterproofing membrane. The Baltimore project used a vapor barrier between the existing structure and the new 3.5-inch topping.
- Shoring plan: Engineers must specify exactly where temporary shoring is needed to support the structure during the creation of the ramp opening and during concrete curing. Rathgeber/Goss Associates, the engineering firm on the Baltimore project, required shoring as the first construction step.
The structural assessment phase typically involves collaboration between the owner, the architect, the structural engineer, and the concrete contractor. Early identification of problematic conditions prevents costly change orders during construction. Adapting parking facilities requires close attention to shifting design loads when deck function changes. Integrating principles from Designing Greener Parking Structures How Mobility Changes Are can help align structural upgrades with broader facility goals.
Demolition and Shoring: Preparing the Deck for a New Ramp
Once the engineering plan is finalized, the first physical step is creating the opening for the ramp through selective demolition. In Baltimore, a separate demolition contractor removed the required portion of the top deck and the existing unit pavers over the new parking area before Bartley mobilized for concrete work. The sequencing of these activities is critical because the structure is at its most vulnerable during the period between cutting the opening and completing the new structural supports.
Shoring Installation Details
Shoring serves multiple purposes in a parking deck ramp addition:
- It supports the dead load of the structure while the ramp opening is being created
- It reduces flexing in the existing floor system caused by moving vehicles on active parking levels below
- It provides a stable platform for formwork during ramp placement
- It protects freshly placed concrete from movement until it reaches sufficient strength
The Baltimore garage was constructed using precast Double T beams, which exhibited noticeable flex under vehicle loading. Andrew Bartley, executive vice president of the Bartley Corporation, observed movement of as much as one and one-half inches on some levels caused by the weight of moving vehicles. The shoring specified by the engineer helped reduce this movement, though some flexing remained where the lower wall met the new ramp and where walls above the ramp contacted the floor above. The contractor used stay forms (forms that remain in place permanently) where the new ramp met the Double T beams on the top deck. These stay forms provided formwork in a location difficult to access and acted as an isolation joint limiting deck movement from reaching freshly placed concrete.
| Structural Element | Challenge Identified in Baltimore Project | Solution Applied |
|---|---|---|
| Double T precast beams | Flex up to 1.5 inches under vehicle loads | Engineer-specified shoring as first construction step |
| Ramp to deck connection | Difficult formwork access at Double T interface | Stay forms left in place as permanent isolation joint |
| Lower wall to new ramp | Residual movement causing minor cosmetic cracking | Cosmetic patching permitted by owner (non-structural) |
| Columns near ramp opening | Insufficient capacity for new ramp loads | Column strengthening before ramp construction |
| Wall below ramp | Required to support new ramp structure | One-side formwork against existing deck and beam wall |
Concrete Construction: Forming the Ramp, Walls, and Beam
With shoring in place and columns strengthened, the concrete contractor can proceed with the new structural elements. The Baltimore project involved several distinct concrete placements, each requiring careful coordination within the tight site constraints of an operating parking garage. Understanding Car Parking Lots and the construction logistics involved in active facilities helps contractors plan realistic work schedules.
Wall Construction Below the Ramp
The first concrete task after shoring was forming and casting a support wall under one side of the new ramp. Much of this wall was formed on one side only, with the other side backed up against an existing deck and concrete beam wall. This approach saved material and labor by using the existing structure as one face of the formwork. Once the ramp was formed and cast, the wall was continued above the ramp level to provide lateral support to the deck above.
Ramp Placement and Tie Beam Construction
The new ramp itself required accurate formwork to achieve the correct slope and transition between levels. After completing the ramp pour, Bartley formed and cast a large tie beam to connect the top deck to the new wall. This beam was critical for distributing loads from the ramp and parking area into the existing structural system. The tie beam also helped control differential movement between the older structure and the new ramp addition.
Concrete Topping Placement
With the structural ramp and walls complete, the next step was installing the 3.5-inch concrete topping over the 46-car parking area. A separate contractor had already removed the existing unit pavers and installed a waterproofing vapor barrier over the deck surface. Bartley then placed the concrete topping over this membrane, creating the finished driving and parking surface.
The topping concrete must meet specific requirements for parking deck applications:
- Adequate compressive strength to resist vehicle tire loads without surface deterioration
- Low permeability to protect the underlying waterproofing membrane
- Proper curing to minimize shrinkage cracking that could allow water penetration
- Good workability for placement in the relatively thin 3.5-inch section
- Compatibility with the waterproofing membrane below to avoid adhesion failures
The Baltimore project also included construction of a large concrete planter on the top deck. This planter served a dual purpose: it separated the new parking area from the remaining terrace space where building occupants could still gather, and it provided an architectural feature that helped the new work blend with the existing rooftop design.
Site Logistics, Challenges, and Quality Outcomes
Working inside an active parking garage in a congested urban area introduces challenges that test even experienced concrete contractors. The Baltimore project required Bartley to navigate tight site constraints, heavy traffic, and the ongoing operation of the facility while completing structural concrete work. These lessons are directly applicable to any contractor considering Automatic Multistoried Car Parking System retrofits or similar urban parking structure projects.
Logistical Constraints and Solutions
The Baltimore parking ramp is located in a busy downtown area, which created several logistical challenges:
- Limited staging area: There was minimal space for construction trucks, cranes, and concrete pumping trucks on site. Trucks often had to take turns occupying the same spots, coordinating with other trades working simultaneously.
- No indoor vehicle storage: Construction vehicles could not park inside the ramp because all parking levels remained open to customers. The crew used a pickup truck to bring tools and materials to work areas.
- Vertical material transport: Most materials were lifted to work areas in boxes using a crane, rather than through the interior of the garage which remained open to traffic.
- Extended delivery times: Heavy traffic in the area lengthened ready-mix concrete and other material delivery times, requiring careful scheduling to avoid cold joints between concrete placements.
- Weather complications: Hot summer temperatures caused a concrete pump blockage when hot concrete plugged the pump line. The crew had to completely clear the pump and clean the line before resuming placement.
Quality Outcomes and Lessons for Future Projects
The general contractor selected Bartley for this project not because the company specialized in parking deck work, but because they trusted the company to deliver careful workmanship and attention to detail. This selection criterion is worth noting: for a structural retrofit in a sensitive urban environment, the quality of execution matters as much as specific experience with parking structures.
The project was completed successfully with the owner satisfied with the result. The ramp and walls turned out well, the waterproofing and concrete topping installation proceeded without issues, and the patching and rubbed finish on the new work made the addition appear as though it had always been part of the original structure. The ramp now serves more customers by adding 150 needed parking spaces to the facility.
Key Takeaways for Contractors
- Thorough structural assessment and shoring design by a qualified engineer is the most important preparatory step. Do not proceed until the shoring plan addresses all deck movement concerns.
- Stay forms where the new ramp meets existing Double T beams provide both formwork access and beneficial isolation joint functionality.
- Keep the facility open during construction but plan for constraints: limited staging, no indoor storage, and shared access with the public.
- Expect residual structural movement even with shoring at connection points. Plan for cosmetic patching and secure owner approval in advance.
- Coordinate waterproofing membrane installation with the concrete topping placement to ensure a continuous moisture barrier beneath the new parking surface.
- Prepare for weather-related concrete placement complications, especially when pumping concrete in hot weather. Have contingency plans for pump blockages.
Adding a ramp to an existing parking deck requires careful coordination between engineers, demolition contractors, concrete specialists, and the building owner. The One E Pratt Street Garage project shows that with proper planning and attention to structural details, a rooftop terrace can be transformed into valuable parking capacity that serves the facility for years to come.