This case study explores a targeted pool deck leak investigation conducted by GCI Consultants at a coastal South Florida condominium, with a focus on drainage system deficiencies, waterproofing membrane failures, and resulting structural corrosion beneath a suspended pool deck. Overall, it demonstrates the importance of detailed envelope diagnostics, integrated waterproofing solutions, and proactive design recommendations to preserve building performance and occupant safety.

The Challenge

The association retained us to investigate reports of water intrusion through an elevated pool deck located above the parking garage entryway at the front of the property. (Figure 1) This leak caused noticeable water damage to the suspended ceiling below, raising concerns about deficiencies in the pool deck drainage.

The elevated deck, which measured approximately 36.5 feet by 27 feet, was situated on the third floor of the north building, adjacent to the gym and pool equipment room. It was constructed with a reinforced concrete structural slab and finished with concrete pavers. Trench and area drains located at the walking surface provided drainage. However, no drainage was provided at the waterproofing membrane level.

Although a painting contractor performed resurfacing work approximately two years prior — likely as an attempt to mitigate water intrusion — leaks continued to affect the areas below. Residents and management reported visible signs of staining, efflorescence, and material deterioration throughout the suspended ceiling, which was framed with steel studs and finished with gypsum board and plaster. Initial repair efforts had failed, and severe corrosion of concealed metal framing raised further concerns about long-term structural performance.

“This project underscores the potential for waterproofing and drainage deficiencies to contribute to deterioration of adjacent systems, including structural framing.”

Methodology for this Pool Deck Leak Investigation

We approached this pool deck leak investigation with a structured, multi-phase methodology designed to identify sources of water intrusion, evaluate the condition of the building envelope, and provide actionable recommendations. As part of our forensic approach, each phase was structured to document observed failures, identify root causes, and provide a defensible basis for corrective action. Finally, the scope of this limited, non-intrusive investigation was completed during a one-day site visit and included the following key components:

1. Document Review

The investigation began with a review of available documentation, including original design drawings, construction plans, as-built records, and prior engineering reports. This background information helped GCI understand the intended pool deck assembly and identify any modifications that may have affected performance.

2. Site Inspection Including Water Spray Field Checks

Subsequently, we performed an on-site visual inspection of the pool deck (Figure 2), suspended ceiling below, adjacent wall assemblies, and pool equipment room. Concealed spaces — such as the interior of the suspended ceiling area — were accessed using existing vent openings and ladders. In an attempt to recreate the leaks at the pool deck drains and the windows, we conducted diagnostic spray testing. This spray testing identified active leak paths contributing to the reported water intrusion.

3. Documentation and Analysis with Recommendations

Upon completion of the site inspection, our team prepared a detailed investigative report outlining our findings and preliminary recommendations. The report addressed:

• Observations from the visual inspection and water spray testing
• Construction assumptions based on concealed conditions
• Structural and envelope-related concerns identified onsite
• Recommended next steps for repair, destructive testing, and long-term maintenance planning

The Results

GCI’s pool deck leak investigation indicated that a likely contributor to the water intrusion was insufficient drainage at the waterproofing membrane level of the structural deck. Existing trench and area drains were limited to surface-level removal and did not provide drainage at the membrane level, allowing water to become trapped beneath the concrete pavers. (Figure 3) Over time, this contributed to membrane deterioration and corrosion of the suspended ceiling framing below. Based on available observations and reported service history, GCI noted that the observed deficiencies may be consistent with original construction design limitations rather than deferred maintenance, though further investigation would be needed to confirm.

Drainage and Waterproofing Deficiencies

The existing deck design included concrete pavers installed over a reinforced concrete slab. Based on typical construction practices, we assumed a waterproofing membrane was present at the structural level, though it was not visible during the inspection. However, this level lacked recessed inlets or drains to evacuate trapped water. Typical best practices for waterproofed decks with overburden recommend positively sloped surfaces and multi-level drainage to avoid hydrostatic pressure. In this case, we noted the following deficiencies:

• Trench drains only operated at the finished surface
• The design did not provide drainage at the membrane level
• Water collected and stagnated directly above the waterproofing

Overall, this drainage deficiency significantly increased long-term risk to the system and accelerated moisture-related deterioration.

Structural Framing Concerns

The suspended ceiling below the pool deck uses steel studs and gypsum board. Consequently, our observations confirmed severe corrosion at multiple framing locations — especially beneath deck drains. The corrosion had likely been occurring over an extended period due to water exposure and contaminants from the pool.

Key structural concerns included:

• Corroded fasteners at the deck-to-stud connections (Figure 4)
  

  Figure 4: Corrosion to metal studs supporting ceiling beneath pool deck

• Deterioration of metal framing supporting the ceiling
• No redundant ceiling support or secondary waterproofing system in place

If unaddressed, the extent of corrosion observed suggested the need for structural evaluation to assess any potential impact on the suspended ceiling’s capacity. GCI recommended that a licensed structural engineer evaluate the framing and develop appropriate repair or replacement plans.

Adjacent Systems and Additional Water Intrusion Sources

Additionally, we identified water intrusion at the following locations:

• Cracks in the deck slab and interface with the pool shell
• The pool collector tank and equipment room
• Poorly sloped stucco at the parapet wall
• Failed and deteriorated sealants at the storefront window assemblies
• Water ponding at the stair landings
  

  Figure 5: Water leaching out at edge of pool deck parapet wall

Our experts observed moisture-related damage and staining throughout the suspended ceiling and within the gym adjacent to the deck. (Figure 5) Furthermore, these issues further supported the need for a comprehensive remediation strategy.

Recommendations for Remediation and Maintenance

Remediation Actions

To restore the pool deck’s performance and prevent further deterioration, GCI recommended a comprehensive repair strategy focused on long-term durability, access, and maintainability:

• Complete removal of overburden and finishes down to the structural slab to expose and evaluate the waterproofing surface.
• Installation of a hot-applied, reinforced waterproofing membrane (e.g., Tremco TremPROOF 6100), selected for durability and resilience in high-exposure applications.
• Integration of a prefabricated drainage mat and protection course to promote continuous drainage and shield the membrane from mechanical damage.
• Recessed installation of new deck drains at the structural slab level to provide proper membrane-level drainage and mitigate hydrostatic pressure buildup.
• Removal and reinstallation of storefront windows to help ensure proper tie-in with the new waterproofing system and address observed corrosion and deteriorated sealants at the window frame anchors.
• Conduct flood testing per ASTM D5957 “Standard Guide for Flood Testing Horizontal Waterproofing Installations” for 48 hours to verify watertightness prior to installing new overburden.
• Development of construction drawings and specifications to guide contractor implementation and maintain continuity across trades for proper execution.

Long-Term Access Maintenance Planning

Moreover, to support long-term performance and facilitate future inspections, we recommended:

• Consider use of modular, removable overburden systems such as pedestal pavers to allow future access to the waterproofing system without requiring full demolition.
• Installation of permanent ceiling access panels beneath the deck to support routine inspection and early leak detection in concealed areas.
• Re-waterproofing of the pool collector tank, equipment room, and stair landings to help eliminate auxiliary sources of water intrusion.
• Engaging a licensed structural engineer to evaluate and design repairs for corroded steel framing in the suspended ceiling assembly.
• Perform additional destructive investigation at the north side of the pool shell, focusing on areas with limited visible access where we could not conclusively rule out the presence of active leakage.

Findings from this pool deck leak investigation highlights the importance of integrated waterproofing and drainage strategies in similar elevated deck assemblies. Overall, GCI’s forensic analysis delivered actionable data and next steps to support remediation and long-term building envelope durability. By equipping the association with clear forensic evidence and prioritized next steps, our team empowered informed decision-making, reduced risk exposure, and long-term asset protection.