Authored by Robert J. Dinjar, P.E., Structural Technical Director, Technical Services
Published June 5, 2026.
Case Study Overview
When concrete spalling and water intrusion began appearing throughout a decades-old pre-cast parking structure, the Rimkus Built Environment Solutions (BES) team was brought in to determine the root cause, confirm the structural condition, and deliver a clear remediation roadmap
|
SERVICE LINE |
ASSET TYPE |
LOCATION |
STRUCTURE SIZE |
|---|---|---|---|
|
Structural Assessment |
Pre-Cast Double-Tee Parking Garage |
Richardson, Texas |
4-Story Building, 6-Level Garage (Roof Used as Parking) |
|
60 ft |
GOOD |
2 |
6 mo. |
|---|---|---|---|
|
Pre-cast double-tee spans: a robust, well-understood structural system |
Overall structural condition: confirmed sound with isolated instances of spalled concrete. |
Waterproofing solutions offered: a cost-effective option and a long-term premium solution |
Monitoring interval recommended for full-length ramp crack: proactive risk management built in |
The Challenge: Spalling Concrete, Water Intrusion, and a Question of Root Cause
For a residential apartment community built around a shared parking garage, the structural health of that garage matters every day. The structure in our case study began showing signs of concrete spalling (chunks of concrete breaking away from the underside of the parking slabs) and ongoing water intrusion. The reports of damage prompted the property owner to seek Rimkus’ expertise in investigating these issues and more beyond the surface.
The parking garage in question was a four-story, six-level, pre-cast concrete structure — a well-established system type that has been used for large-span parking applications since the 1980s. The 12DT30 double-tee members spanning 60 feet were a proven and durable structural solution, but like all structures, they require maintenance as they age. The visible symptoms of spalling, efflorescence, water staining, and deteriorated sealants raised an important question:
Is the observed spalling and water damage a sign of structural deterioration in the double-tee system itself, or does it have a specific, addressable cause that can be corrected before it spreads further?
The Approach: Identifying the Mechanism, Not Just the Symptoms
The Rimkus BES team conducted a comprehensive visual structural inspection of the parking garage, focusing on each major component of the pre-cast system, including:
Pre-cast double-tee members
- Inspected all 12DT30 slabs across the six levels for signs of deflection, cracking at midspans and ends, overloading, and structural deterioration
Connector tabs and transition joints
- Inspected the metal connector tabs embedded at the joints between double-tee members, which are a known vulnerability in any pre-cast system exposed to water intrusion
Sealants and backer rods at thermal movement joints
- Inspected transition zones between barrier walls and columns, where thermal cycling causes progressive sealant breakdown.
Fourth-floor drainage system
- Inspected the roof deck drain areas, where vehicular traffic creates movement stress on the surrounding concrete, causing seals to fatigue quickly
Top-floor ramp slab
- Inspected the access ramp concrete, which showed a full-length crack, requiring further assessment and a monitoring decision
A crucial part of the Rimkus approach was tracing the visible damage back to its origin point in order to understand the underlying failure mechanism — a distinction that shaped both the findings and the remediation recommendations.
Key Findings: A Sound Structural System and a Solvable Issue
The most important finding of the inspection was also the most reassuring: the pre-cast double-tee structural system itself was in good condition. No deflection, bending, or overloading was observed across the 60-foot spans. The structure was performing as designed.
What was failing and creating the spalling was the embedded metal connector tabs at the transition joints between double-tee members. Years of uncontrolled water intrusion through deteriorated joint sealants had allowed moisture to reach these metal components, causing oxidization. As the metal corroded and expanded, it cracked and pushed away the surrounding concrete, creating the spalls visible on the underside of the slabs. The damage was not structural in origin, but would continue to spread without intervention.
|
Component |
Rating |
Key Finding |
Recommended Action |
|---|---|---|---|
|
Pre-cast double-tee structural system (60 ft spans, 12DT30 with 2″ topping slab) |
Good |
No deflection, bending, or overloading observed; structural system performing as designed |
No structural intervention required |
|
Concrete spalls at double-tee connector tabs — underside of slabs |
Fair |
Water intrusion causing oxidization of embedded metal connector tabs, driving localized concrete spalling; not structurally critical if remediated |
Chip back to sound concrete, clean and prime tabs with corrosion-resistant primer, apply bonding agent, and restore to original profile |
|
Transition joint waterproofing between double-tee slabs |
Fair |
Deteriorated sealant and backer rod allowing uncontrolled water intrusion — primary driver of connector tab corrosion and spalling |
Option A (routine): Two-part polyurethane sealant with 3-year maintenance cycle. Option B (long-term): Sikadur Combiflex SG membrane with metal cover plate protection |
|
Sealants at thermal movement joints — barrier walls and columns |
Fair |
Age and thermal cycling causing sealant deterioration at wall-column interfaces, with exposed metal surfaces at risk of corrosion |
Remove debris, apply anti-corrosion paint on exposed metal surfaces, install new flexible sealant |
|
4th-floor drainage system — concrete spalling around roof deck drains |
Fair |
Spalling around drain openings caused by movement from vehicular traffic above; localized but requiring repair to prevent expansion |
Chip back to sound concrete, apply bonding agent, patch to original conditions |
|
Top-floor ramp — full-length slab crack |
Monitor |
Crack spanning length of slab, currently under 1/4 inch width; localized and not immediately structural, but requires monitoring |
Route and fill with flexible polyurethane sealant; monitor every 6 months and notify Rimkus if crack width increases |
One of our recommendations to highlight is the two-pathway approach to transition joint waterproofing. Recognizing that owners operate under different capital planning horizons, the Rimkus team offered two distinct options:
- Maintenance-cycle solution: a cost-effective polyurethane sealant system with a 3-year replacement schedule
- Premium long-term system: a Sikadur-Combiflex® SG System with metal cover plate protection for extended service life
This dual-option framework empowered the owner to make an informed, budget-appropriate decision rather than being locked into a single prescribed approach.
“Understanding why concrete is failing is as important as knowing what to do about it. The right repair, applied to the wrong diagnosis, solves nothing.” – Robert J. Dinjar, P.E., Structural Technical Director, Technical Services
The Value Delivered: Clarity, Choice, and a Clear Path to Stopping the Damage
The Rimkus BES assessment delivered value at every level of the decision-making process — from the structural engineer reviewing the findings to the asset manager planning the capital budget.
|
Root Cause Identified |
Structural Clarity |
Tiered Repair Options |
|
The assessment went beyond visible symptoms to identify the actual failure mechanism: uncontrolled water intrusion oxidizing embedded connector tabs and driving spalling from the inside out. |
The BES team determined the double-tee structural system remained sound, with no deflection or overloading. This confirmed that the observed damage was a maintenance issue, not a structural emergency. |
Rimkus provided two waterproofing solutions to the client: a cost-effective short-term option and a premium long-term system. |
|
Corrosion Arrested Before Escalation |
Proactive Monitoring Protocol |
Long-Term Asset Value Protected |
|
Left unaddressed, oxidizing connector tabs would continue to expand, driving progressive spalling across the structure. We delivered a new remediation sequence to interrupt the harmful cycle: clean, prime, restore, seal. |
For the full-length ramp crack, Rimkus built a 6-month monitoring protocol into the recommendation. The protocol is a structured process to detect any change in crack behavior before it becomes a more serious concern. |
The targeted remediation and waterproofing recommendations will protect the value of the pre-cast double-tee parking structure by halting the deterioration cycle before it becomes irreversible. |
Why Pre-Cast Parking Structures Require Special Assessment
Pre-cast concrete double-tee systems are among the most durable structural solutions in the parking industry. Unfortunately, their long-term performance is heavily dependent on the integrity of the joints, connections, and waterproofing systems that tie the individual elements together. When those systems fail, water finds a path. If the water reaches embedded, metal components in a pre-cast system, the deterioration that follows is well understood, progressive, and predictable by qualified professionals.
General-purpose building inspections often miss the specific failure patterns that characterize aging pre-cast systems. The Rimkus BES team brought specialist knowledge of pre-cast construction to this assessment, including familiarity with the PCI 12DT30 system type and its known aging characteristics. Our team’s combined expertise helped them interpret what they observed, not just as isolated defects, but as part of a coherent failure sequence with a clear intervention point.
For property owners managing aging parking structures, the level of diagnostic precision is often the difference between a reactive repair cycle and a proactive asset management strategy. The Rimkus experts on this assignment were able to give the client both the clarity to act now and the framework to manage the asset’s condition over time.
Key Takeaway
By identifying the root cause — connector tab corrosion driven by uncontrolled water intrusion — rather than simply cataloguing visible damage, the Rimkus BES team delivered a remediation roadmap that addresses the mechanism, not just the symptoms. That distinction is what makes a structural assessment genuinely useful.
Why Choose Rimkus Built Environment Solutions?
The Rimkus BES team provides specialized structural assessments for pre-cast and cast-in-place parking structures. Our experts are skilled in delivering root-cause diagnosis, condition ratings, and actionable remediation guidance that protects clients’ assets for the long term.
We provided the following structural engineering and assessment capabilities for this case study, and can offer additional integrated services.
- Pre-Cast Concrete Structural Assessment
- Double-Tee Parking Garage Inspection and Evaluation
- Concrete Spall and Corrosion Root Cause Analysis
- Connector Tab and Transition Joint Condition Assessment
- Waterproofing System Evaluation and Remediation Recommendations
- Tiered Repair Solution Development (Short-Term and Long-Term Options)
- Sikadur-Combiflex® SG System and Polyurethane Sealant System Specification
- Concrete Crack Documentation and Monitoring Protocols
- PCI System Knowledge (12DT30 Double-Tee Members)
- PE-Supervised Engineering Reports for Property Owners
Seeing signs of spalling, staining, or water intrusion in your parking structure?
Connect with a member of our Texas team or submit a request for consultation today!
Meet Our Texas Expert: Robert J. Dinjar, P.E.
Structural Technical Director, Technical Services
Built Environment Solutions, Texas
+1 512 492 2290
[email protected]
View Robert’s Expert Profile
Robert Dinjar specializes in preparing structural engineering designs, designing building lateral resistive systems, and the inspection and certification for high wind and flood compliance. He has experience working with a wide range of structures including commercial buildings, residences, retaining walls, and pools. Robert provides other built environment services such as remediation, construction defect evaluation, structural failure analysis, and storm and flood damage assessment.
This case study is intended to provide general information and insights into prevailing industry practices. It is not intended to constitute, and should not be relied upon as, legal, technical, or professional advice. The content does not replace consultation with a qualified expert or professional regarding the specific facts and circumstances of any particular matter.