By: Jimmy Monahan
Published: March 26, 2020
For Part I – Click Here
Balconies should be regularly maintained. It is imperative that clients have a Professional Engineer or Registered Architect provide essential guidance for regular required maintenance to ensure that their concrete balconies hold up during their full-service life. In order to reach a full-service life, regular inspections must be performed by a Qualified Engineer or Architect. These inspections are necessary to identify potential new issues and to ensure that existing conditions do not worsen over time. These conditions may include cracks in the topside and/or underside of the concrete slab, spalling of the topside or underside of the slab, loose railing connections, damage to the waterproofing membrane (if there is one), and ponding water. Building maintenance staff should annually inspect the balconies to clean the concrete surfaces and ensure that drains are not clogged.
Annual inspections by the building maintenance staff can help to prevent overloading the balconies during their lifespan. It is commonplace for residents to install tile or wood deck surfaces atop the concrete slab to change the aesthetic. The balcony was likely not designed to accommodate the increase in load. An accumulation of other items are frequently found on the typical balcony, such as large planters, patio furniture, storage cabinets, decorations or an overflow of items to be stored. Over time, additional weight and overloading may incur irreversible negative effects on the service life of the balconies.
Additional sustained loads increase the short and long-term deflection of the cantilevered concrete slabs. “Concrete creep” is a condition that can deform the slab and progressively worsen with time. This change in shape can drastically affect the positive drainage capacity of the balconies, preventing water from reaching the drain(s). As a result of improper drainage, ponding water can promote water infiltration. Insufficient waterproofing membrane will compound the resting water and allow it to infiltrate the slab, wreaking havoc on the structural reinforcement. Internal cracks will expand and contract during freeze-thaw cycles and the corrosion of the reinforcing steel will cause the concrete to spall and fail.
Solving the issue of ponding/resting water is not typically a simple fix, especially when the slab has significant negative pitch away from a drain. The obvious choice is to provide new pitch to the slab through the application of a concrete topping, where a Contractor would build up the concrete with a positive pitch enough to adequately drain the water. However, this is a shortsighted solution, as this method increases the sustained load on the slab. A slope minimum of 1/8” to 1/4 ” per linear foot is the industry standard for promoting positive drainage on a concrete slab; depending on the size of the balcony and the location of the drain, a substantial amount of concrete build up may be required to provide sufficient positive pitch towards the drain. The more pronounced the existing creep and deflection on a balcony, the more concrete is needed to correct the negative pitch. A 1” layer of standard concrete weighs approximately 12.5 pounds per square foot, so this additional load may potentially exacerbate the long-term deflection and creep of the structure. A counter measure to add positive pitch may, in time, end up causing repeat localized failures due to overloading.
Small cracks or seemingly trivial ponding water issues have the potential to snowball into much bigger ones if not addressed in a timely manner. In order to ensure the structural integrity, a balcony requires regular maintenance; the drains must be cleaned, cracks formed in the concrete should be repaired and sealed, and sealant joints at the railings and slab-to-wall transitions must be kept watertight. Addressing deleterious conditions early and comprehensively, will help ensure the repairs are more cost effective and manageable. The building maintenance staff who regularly inspect balconies may identify damage and/or deficiencies, such as a waterproofing membrane system that may have been damaged when a piece of furniture was dragged across its length. It is important for building owners and maintenance staff to regularly communicate with their engineers and/or architects to create a plan for cyclical inspections, maintenance and repairs in order to prevent large order of magnitude repairs that are identified as unsafe conditions or cost prohibitive.