Most residential buildings have balconies. These areas are an urban oasis for people to enjoy the vistas of high-rise living, get a breath of fresh air, or simply carry on a casual conversation with their neighbours. They are an important part of the day-to-day fabric of building vibrant, caring, and cohesive communities in dense urban residential areas. Balconies may also have more technical purposes, such as being an area of refuge in case of fire or forming deliberate sun shades to reduce cooling needs by keeping the hot summer sun from over-heating the units.
The most common method of constructing balconies is steel reinforced cast-in-place concrete. As we build concrete buildings, formwork is set at each floor level, with two layers of reinforcing steel placed in the forms, and concrete is poured to encapsulate the steel and take the shape of the forms. Once the concrete is set, the forms are pulled and moved to the next floor. In each layer of steel, upper and lower, the bars may be placed in a manner such that they are aligned both parallel and perpendicular to the walls.
Why do we go to such trouble? Steel and concrete work well together, because concrete is good in compression but poor in tension, steel is good in tension but poor in compression, while combined they offset each other’s weaknesses, and perform well to resist shear forces too. Bending something causes one side to be put in tension and the other in compression. Floors and balconies bend due to their own weight, the weight of the various things they hold up (railings, walls, finishes) and the loads of people and furnishings. Resisting gravity – or holding things up – results in shear forces at the location where the thing is held up. Now you know why the side walls of balconies are called shear walls. If there are no shear walls, then the balcony is cantilevered (projecting like a wide diving board) from the main floor structure.
To keep people from falling off balconies, guards (railings some may say) are placed across the open sides of the balcony. Some guards have vertical pickets, some solid metal panels, and some glass or plastic panels. They all must be at least 1,060mm (42 inches) tall when measured from the balcony walking surface and must resist specified loads from both people and wind. Oddly enough, because they are fastened to the balcony slab, they are often the cause of deterioration or damage.
In many ways reinforced concrete is man-made stone. The intention is to have a building material that is very long-lived and relatively maintenance free. As Samuel Johnson said, “Hell is paved with good intentions.” Reinforced concrete deteriorates over time due to a combination of many factors, including:
- Cracks, from drying, daily and seasonal changes in moisture and temperature, and people loads.
- Carbonation, a chemical reaction with carbon dioxide that raises PH level in the concrete.
- Rusting steel, from precipitation getting into the cracks or carbonation progressing to the steel.
- Spalling, because rust occupies more space than steel and causes the concrete to suffer tensile stresses which it is not as good at resisting, so it pops off.
Once the concrete starts to fall-off the steel starts to accept compression forces, which it is not so good at resisting, and the people and property below are exposed to dangerous conditions.
So, just as most residential buildings have balconies, all of them will eventually undergo a balcony repair project. When the project will happen is difficult to predict but it seems from our files likely that the 25th to 40th year of service is a common range for major repair and replacement work to be needed.
These repairs are very noisy. Jack hammers must be used to break away the bad concrete. Grinders are needed cut away damaged steel. Motorized brushes are used to clean the remaining steel. Compressed air is used to clean away dust and small debris. They are also very disruptive. People and parking are prohibited from being below the work. You have no balcony while the work is ongoing. Workers will appear, seemingly from nowhere completely unannounced in front of your balcony windows and doors.
Knowing what we know now, there are strategies during the repair work that can help prolong the life of any original materials that could be salvaged, and the new materials provided, including:
- Concrete mixes that include corrosion inhibitors.
- Epoxy coated steel, or even stainless steel, reinforcing to resist corrosion.
- Thick waterproofing membrane coatings capable of withstanding pedestrian traffic and balcony furniture scuffing on the balcony floor surface.
- Thin paint finishes on the balcony soffit (underside) to inhibit carbonation progress and improve aesthetics.
- Balcony guards that improve visibility from within the units or reduce overall maintenance requirements.
With the passage of time, and the ongoing deleterious effects of the environment, balcony repairs are inevitable. Planning for them by saving early and monitoring their condition by regular in-house and intermittent independent evaluations will ease some of the stress. Communicating the need for the work and listening to the concerns will help smooth the path of completion the work successfully.
Jon Juffs, Director, Condominium/Strata Group
Jon Juffs is the Director of the Condominium/Strata Group at McIntosh Perry. Since 1988, Jon’s work experience has been continuously focused on architectural technology and building science services for many forms of occupied buildings. In 2006, he co-authored ‘Reserve Fund Essentials’ – a layperson’s guide to reserve fund planning and control. His service motto is “A home is more than roof or walls or lofty curving stairs … it’s a people thing after all.” Jon is a long-time volunteer member of CCI – Huronia (past President & current Board Member), as well as the CCI – Toronto & Area Chapter (Professional Associate), CCI– National (Certification Committee member), past ACMO (Regional Committee member).