Project Spotlight: Penthouse Pool Deck Reviews & Repairs
- Penthouse pool deck located at a 11-story condominium high-rise in Allston, MA
- Cast-in-place concrete, steel and masonry construction built in 1987
- Leaking into living units and common areas for years
- Pool deck area is roughly 2500 SF and is split-slab: structural slab with a waterproofing membrane and a concrete topping slab
- There are four (4) drains – three in the form of two (2) trench drains – one trench drain on the east side of the pool, and one trench drain on the south side of the pool; and one (1) drain that is north of the east trench drain. This single drain is approximately 3” in diameter and appears to have been installed after construction. The east trench drain is oriented north-south. This trench is drained by two (2) 4” drains. The south trench drain is oriented east-west and is drained by one (1) 4” drain. A review of the drains revealed that they are all clogged with debris
- There are two (2) masonry planters that border the pool on the south end. They are clad with a wood lattice veneer. They drain by directing water onto the concrete topping slab and into one of the trench drains.
- Numerous cracks in the topping at various locations throughout the pool deck
- Various locations in the pool deck that have been repaired previously as indicated by differences in patching materials and sealants used
- Areas of ponding water on the pool deck as evidenced by puddles in front of a storage room door, located on the north side of the pool deck. A look into the storage room revealed water leaking into the room from the pool deck.
Test Cut Results
The pool deck consists of (from top to bottom):
- Concrete topping slab: varies in thickness from 1¾”to 5½”
- Rigid insulation: varies in thickness from 1” to 2”
- Protection board: +/- ⅛”
- WP membrane
- Structural concrete deck
At each test cut location, there was moisture. Some of the locations had standing water, indicating that there is no manner in place to drain away water that gets trapped between the topping slab and the structural slab. In addition to the moisture/water accumulation, there are indications that this has been ongoing for quite some time. These indications are in the form or fully saturated rigid insulation at most locations and partially saturated at the rest; deformities and discoloration of the rigid insulation that is in contact with the protection board – these are due to constant presence of water. In addition, deformed rigid insulation was observed at the pool edge excavation. It appeared as though the insulation may have been melted as if by a torch during construction; however, given the sequence of installation there should not have been any need for torching once the insulation was installed. Another explanation and one that is more probable, is the chlorine from the pool was deforming the insulation. This makes sense once the area was fully excavated and the “melted” pattern appeared to be in the shape of a puddle of water as if it was coming from the pool.
Summary and Recommendations
- Complete removal of the concrete topping slab; rigid insulation and all waterproofing membrane and protection board. Remove trench drain bodies but maintain the associated piping for new drains.
- Route and seal and cracks or joints in the structural slab. Perform any other repairs such as spall repairs.
- Engage a professional land surveyor to establish grades of the pool deck for proper pitch
- Apply mortar to achieve proper pitch if the survey determines it is required
- Install a waterproofing membrane that is resistant to chlorine
- Install a paver system as the pedestrian surface