St. Philips Gate, Worcester Park
Structural Renovations has just completed repair and stabilisation works to the reinforced concrete within the subterranean garage of a private block of residential apartments in Surrey.
Background
St. Philip’s Gate is a private gated development, built approximately 20 years ago and is built on the grounds of the former Church of St. Philip, which was demolished in the mid-1980s. The churchyard and war memorial are still present and lie directly next to the apartment block.
Our works were concerned with extensive remedial work to the car park deck slabs, which were badly displaced and severely cracked, having been constructed on unstable ground. In addition, we were tasked with completing repairs to the columns supporting the main residential structure above.
Survey & Preparation
With site handed over to us we cleared and closed off the car park to allow us to fully survey and identify all defects. Close co-ordination with the clients building surveyor minimised delays and allowed us to agree and vary the scope as the project progressed. Fosroc UK were approached to supply suitable products to remedy the issues being experienced on site.
Resin Injection to Cracks
Numerous areas of cracking were present across the entire deck. Using Fosroc Nitofill epoxy resin (both low viscosity and thixotropic – depending on crack width), injected through proprietary injection ports, it was possible to seal the crack to the depth of the slab and effectively bond both sides together.
Resin Injection and Crack Stitching
Some of the cracks were considered too severe to receive the resin injection process alone and additional structural works were instructed. Either side of each of the designated cracks the concrete slabs were drilled at regular centres, at an approximately 45-degree angle, across the crack and the resultant holes were vacuumed to remove loose materials and dust. Each hole was systematically filled with Fosroc Lokfix E75 (2 part epoxy resin), into which pre-cut lengths of threaded stainless steel rod were inserted to approximately 10mm below the deck surface. In additional to the crack stitching we also resin injected the cracks using the process detailed above.
Deck Slab Levelling
Over time the individual concrete deck slabs had displaced through a combination of ground heave and subsidence. This had resulted in uneven surfaces and trip hazards for those using the car park. It was agreed that without the costly and major reconstruction of the car park deck in its entirety it would not be possible to alleviate all of the surface undulations and a degree of compromise was necessary. Areas of subsidence were broken out, prepared and reinstated using a combination of Fosroc repair mortars (both hand placed and flowable). Areas of the slabs where heave had occurred were broken out and ground down (ensuring embedded reinforcement was not compromised) and made good with Fosroc UK’s hand placed mortars.
Concrete Frame Repairs
Isolated areas of reinforced concrete columns had begun to deteriorate and also required attention. These defects were not considered serious and therefore no temporary propping was required. The defects were broken out and square cut and all exposed reinforcement was treated using Fosroc Nitoprime Zincrich Plus, before being reinstated using Fosroc Nitobond HAR and Fosroc Renderoc HB45.
Completion
As all the works were completed undercover, we were not affected by the heavy rains experienced throughout most of the project but the cold conditions did hamper progress at times. Ultimately, we were very happy to hand the site back to a satisfied client both on time and on budget.