What a podium slab does
In many mid-rise buildings, a concrete podium supports wood-framed floors above and parking, storage, or commercial space below. Where the podium is exposed as a courtyard, plaza, or planter, it acts as a roof over the occupied space underneath.
Waterproofing on a podium is usually covered by other layers, often called overburden. Pavers on pedestals, topping slabs, soil, planters, and hardscape sit above the membrane, with protection and drainage layers between them. Drains are often set to collect water at both the surface and the membrane level.
Slope matters at the membrane, not only at the finish surface. Water that reaches the membrane must be able to drain, either from slope in the slab or from tapered materials placed above it.
Where podium waterproofing fails
Transitions cause many podium leaks. The membrane must turn up walls, tie into the barrier of the wood-framed building above, and seal at door thresholds, curbs, planters, and expansion joints. Each turn and termination is a place where laps, upturn height, and sequencing can go wrong.
Penetrations add more. Drains, pipes, conduits, and posts that pass through the membrane need flashing details that suit the membrane chosen. Damage from later trades working over unprotected membrane is a recurring concern. Roots from planters can also damage membranes that lack root protection.
Below, leaks show up as staining, efflorescence, and mineral deposits on the underside of the slab, sometimes with dripping onto vehicles or finishes. Water that reaches reinforcing steel can lead to corrosion over time.
Investigating a podium deck leak
Because the membrane is buried, investigations start with the drawings, specifications, product submittals, and any construction records. Leak locations below are mapped against the plan above: drains, planters, joints, walls, and penetrations.
Testing narrows the source before overburden is removed. Flood testing, described in guides such as ASTM D5957, holds water on a defined area to see whether it leaks. Electronic leak detection can locate breaches in some membranes. Where the parties agree, selected overburden removal exposes the membrane and its transitions.
We use state-of-the-art cameras and video documentation techniques to provide trial-ready exhibits. If membrane materials appear to have manufacturing defects, we are aligned with several laboratories that test and analyze product failure. Field samples are kept at our office in case they are needed at trial.
Plan review and repair scopes
Gregg de Haan specializes in plan reviews as they relate to waterproofing above and below grade. On podiums, the details at walls, doors, and drains often decide whether the system can perform as built.
Podium repairs can be extensive because overburden must come off before the membrane can be repaired or replaced. Our conceptual repair scopes and cost estimates describe the extent of that work so the parties can evaluate it on the same information.
Sequencing matters as well. Work on an occupied building may need to be phased around access, parking, and residents, and the estimate should reflect that.
Common warning signs
- 01Staining, efflorescence, or mineral deposits on the garage ceiling
- 02Dripping water below courtyards, planters, or drains
- 03Rust staining at cracks on the slab underside
- 04Ponding on courtyard surfaces after rain
- 05Damp or damaged finishes at walls next to the podium
- 06Leaks at doors that open onto courtyards