Gunwharf Quays is home to over 90 brands, the outlet centre occupies a prominent waterside location in the heart of Portsmouth's historic maritime quarter, adjacent to Portsmouth Harbour and the iconic Spinnaker Tower.

The Challenge

During planned structural alterations to expand the retail area, principal contractor Conamar uncovered a waterproofing failure beneath the existing flooring. Left unaddressed, the failing membrane presented a serious risk of water ingress, threatening both vehicles in the car park below and the long-term integrity of the structure itself.

Conamar engaged Newton Waterproofing alongside specialist contractor QST Construction Services to deliver a remedial waterproofing solution.

The Solution

QST Construction's experienced team worked closely with Newton Waterproofing to specify a complete beam and block deck waterproofing system and to establish the correct installation methodology from the outset.

Thorough substrate preparation was identified as a critical first step. QST removed all existing failed waterproofing materials, mechanically prepared the substrate to eliminate contaminants, and verified the deck's suitability to receive a new system before any product was applied.

Following preparation, QST installed PolyMaxx HA - a BBA-approved, seamless, hand-applied, fibre-reinforced membrane system designed for use on decks, flat roofs, balconies, and walkways. The system's advanced curing technology allows each coat to cure in approximately 30 minutes, enabling the full installation to be completed within a single working day. The result is a flexible, durable membrane that is fully bonded to the substrate, preventing water tracking across the deck.

Challenges Overcome

The working area offered no weather protection, the installation took place during winter, and persistent water ingress at the perimeter edges required bespoke additional detailing to ensure a fully sealed system. Despite these conditions, the QST team maintained progress and consistently high workmanship throughout.

The Result

The completed installation was subject to a rigorous 36-hour flood test at a depth of 80mm. No leaks were detected, confirming that all areas of the concrete deck had been fully and effectively waterproofed to the required standard - a significant achievement given the site conditions and the high-profile nature of the project.

Contractor Testimonial

Bradley Hartley, Project Manager at QST Construction Services, commented that the PolyMaxx HA system was highly user-friendly, enabling efficient and consistent application throughout the project. He noted that, when conditions allowed, works advanced smoothly and to a high standard.