Remedial works at a courtyard complex in Dee Why have stopped planter-box leaks that threatened interior finishes, terrace tiles and the post-tensioned podium slab below. MJ Engineering Projects inspected two twenty-metre planter boxes, traced every moisture path and produced a remediation programme that waterproofed the planters, retiled the terraces and upgraded façade elements without pausing day-to-day building maintenance. The finished system now meets National Construction Code (NCC) requirements and the waterproofing expectations of the NSW Design and Practitioners Act.
Project Background
Residents noticed ceiling stains and musty odours in the units adjacent to two large courtyard planters. MJ Engineering Projects deployed moisture mapping confirming failed membranes. Because the planter boxes sit on a post-tensioned slab and are bounded by load-bearing beams, drainage corrections had to avoid weakening structural elements. Our remedial design practitioners formulated an NCC-aligned specification and sequenced works so routine building maintenance services could proceed as usual.
Scope of Remedial Works
- Waterproof planter boxes
- Waterproof and tile terraces
- Replace terrace doors
- Apply medium-build acrylic coatings
- Apply low-sheen acrylic coatings
- Repair concrete spalling
- Replace cavity flashings
- Repair delaminated render
- Apply joint sealant
Key Challenges and Solutions
Correcting planter slope without altering downpipe falls
Leakage originated where stagnant water sat on a near-level planter base. Our remedial engineering team installed a sheet membrane, then laid lightweight screed to create adequate falls.
Integrating membrane, flashing and drainage to satisfy the Design and Practitioners Act
The remedial specification required continuous waterproofing that protects adjacent areas. Torch-on sheet membrane was used to provide a water barrier that aligns with the performance intent in accordance with Australian Standards and the NCC.
Retrofitting vertical drainage through a beam-supported planter
Original drainage pipes ran horizontally ontop of the slab as no allowance for drainage outlets were allowed in the slab during construction. Furthermore, as the slab was post tensioned, radar scanning located post-tension tendons and reinforcing bars so our structural engineer could mark safe coring locations clear of the structural elements.
Conclusion
Unchecked planter-box leaks undermine slabs, damage interiors and increase insurance costs. These remedial works sealed the planters, retiled terraces and renewed façade details while residents remained in place and normal building maintenance continued. Waterproof membranes now slope to strip drains, new flashings block moisture migration and low-sheen acrylic coatings provide uniform UV protection.
MJ Engineering Projects combines more than fifteen years of remedial works experience with practical building-maintenance insight to solve planter, balcony and façade failures across Sydney. Explore additional case studies on our blog or contact the remedial works team for tailored advice on waterproofing, drainage upgrades and structural repairs.
