Creative solution to remedy render failure

Following our article on repair and renovation of an occupied building, CK Dickson Wong , Senior Associate, Toronto, discusses a project where Inhabit’s team developed a creative alternative to paint and render re-application.

The existing façade of the building – which is primarily painted cementitious render over concrete substrate – started exhibiting render failure not long after completion. Extensive cracks developed over large areas of the façade, particularly at the joints between structural members and infill walls. Adhesion failure was also observed upon hammer tests at selected locations.

Inhabit carried out a full survey of the building and was able to identify and document areas where removal and repairs are needed. Paint and render re-application proved to be problematic, as it was difficult to match the colours of the repaired patches with the existing painted surface. In addition, it was a site-executed, labour-intensive process that required workers to work at height over an extended period. As such, the repair work would have been expensive, dangerous, slow, of uncertain quality and aesthetically unsatisfactory. Not to mention also that the building needed to be fully functional during construction – the extensive scaffolding works would have hindered the building’s day-to-day operation over a long period.

Instead of re-applying paint and cementitious render over locations where failed render had been removed, Inhabit proposed using a modular, factory-assembled metal cladding system to clad over some areas. The objective was to minimise the amount of site work and therefore, what started as a technical task evolved into an architectural design exercise, as Inhabit designed, presented, documented and obtained a building permit for what essentially was a re-designed elevation with new aluminium features. Several factors needed to be taken into account in the exercise:

• Alteration of development parameters: Building a cladding system outside the existing boundary of the envelope may trigger changes in GFA that require government review and approval (as was the case in this project). Other planning-related restrictions also need to be reviewed. Thorough understanding on the statutory constraint on planning is needed.
• Building tolerance: Site survey revealed that much of the existing structure was out of tolerance specified in the specifications (consequently the thickness of the existing render varied greatly across the building, which was likely to have been one of the contributing factors of render failure). As such any new systems would need to accommodate deviations measured on site.
• Structural capacity: New post-fixed anchorages on the existing structure were needed for the new cladding system. The thickness and structural capacity of the existing structure needed to be measured and verified by tests.
• Phasing, protection and logistics: To ensure continuous operation over the course of construction, the refurbishment works were phased to minimise their impact. Phasing, protection and logistics required coordination with the client’s operation team during the early stages of design. Locations of material storage, transportation and equipment operation zones are not typically captured in an architect’s design process – contractor’s input at early design stages is preferred.

Inhabit’s specialists integrate their experience on occupied buildings, and feed this back into the design phase. This means they are able to predict challenges and design for resilience noting the foreseeable climatic challenges, notwithstanding the construction quality obligations of the contractor which influence the outcome.