Moisture
Water vapour in the air as well as bulk moisture must be addressed in the overcladding design. Rainscreen-type overcladdings drain behind the exterior finished wall, while barrier enclosures such as EIFS drain at the exterior plane.
The chosen building overcladding application should balance moisture inside and outside the building, and allow the building and the enclosure assemblies to dry out. Moisture accumulation inside the building and within the enclosure should be offset by equivalent drying.
One concern for overcladding is the potential for trapping excess moisture within the building but also within the enclosure assembly itself; for example, between the new exterior cladding and the original masonry walls. To limit the negative effects of excessive condensation—which can lead to oxidation, deterioration of building materials, and potential mould occurrence—the project specifiers and architects should have designers determine how much water vapour could be generated within the building and determine the resultant increase in internal vapour pressure above the external air. After making this determination, the performance expectations and physical properties of the enclosure assemblies can be assessed.
Overcladding for performance
These solutions are complicated and challenging to explain to stakeholders who are not building professionals. Once the project team has the confidence of decision-makers, a community will be able to enjoy a piece of its legacy, an iconic architectural landmark, for decades to come. After all, in addition to providing the setting for teaching and learning, school buildings in many cities and towns are frequent places where residents of those communities go to vote, attend meetings of various kinds, gather for social and cultural events, and participate in other types of civic engagement.
Masonry strengthening, facade overcladding, and targeted expansions represent cost-effective approaches to making the most of existing K-12 schools, university buildings, civic structures, and older commercial and residential architecture. The approach can benefit a wide and diverse group of users. They can also contribute to improved neighbourhood cohesion, helping to celebrate and build upon the legacy of each existing or historic building.
Case studies: Urban public schools
These conditions may be seen in older school buildings. Unfortunately, the combined forces of time, climate, and lagging maintenance can leave school districts’ facilities teams with significant, and often unexpected challenges. Schools typically age faster and funding to fix them is allocated.
