Waiting for the next calamity is not an option

Galleries and balconies of older residential complexes often rest on concrete consoles. Inadequate or overdue maintenance combined with chloride e-indentation from the use of road salt make the brackets vulnerable to corrosion of the reinforcement. Periodic maintenance, inspections and surveys can prevent high repair costs over time or worse, structural failure. "We really need to take action."

The Netherlands has a very large number of residential complexes built in the 1960s and 1970s. A typical feature of most of these apartment buildings are the concrete consoles on which galleries and/or balcony slabs rest. To keep the joints and dilatations between the gallery and balcony slabs watertight, caulking joints or bibs were usually used. These seals have a relatively limited remaining life; periodic replacement or repair is required. This is because if there is insufficient waterproofing, rainwater can penetrate the joints and get onto the tops of the brackets. 

Frost

"The combination of moisture and chloride in the reinforced concrete structure can cause chloride-initiated reinforcement corrosion," begins Robin Hartmann, director-owner of Bejan Bouw & BetonTechniek Adviesburo. "The corrosion reduces the diameter of the reinforcement and thus the load-bearing capacity. With pitting corrosion, there can be localized rebar diameter decreases, sometimes as much as 30% of cross-sectional area. Most problems are caused by residents fighting slipperiness on balconies and galleries with road salt in times of frost. But in the 1960s and 1970s, chloride salts were also mixed into the concrete structure as a pavement accelerant. All these buildings are coming of age and we're going to see a spike in problems now."

Biggest moment

Most concrete consoles are constructed as monolithic cantilever beams connected to interior walls or the interior structure. Hartmann: "The main reinforcement of consoles is at the top, the greatest moment is at about one-third of the cantilever length from the exterior wall. It is precisely at that location that the penetration of moisture and chlorides is greatest as water moves toward the façade. Many damages are due to overdue or inadequate maintenance and are therefore basically unnecessary. A housing association or homeowners' association that cuts back on this can actually run into huge repair costs in the future. Again, prevention is better than cure. With periodic maintenance and timely replacement of improperly functioning expansion joints and finishing layers, the penetration of rainwater and de-icing salts can simply be prevented."

Drill Tests

Finding out what conditions consoles of a building are in requires research. "Among other things, Adviesburo Bejan carries out inspections and investigations, identifies the problems, gives advice for repair and, if requested, also supervises implementation," Hartmann continued. "In principle, inspecting consoles is not easy, since you cannot reach them from above. Therefore, we make random drill holes in different areas in combination with reinforcement scans, in such a way that we do not touch the reinforcement. Our material examination then reveals the severity of the problem. It may be that there is the presence of chlorides, without safety risk, then it may be advisable, for example, to protect the concrete structure with cathodic protection. If the load-bearing capacity is affected, then a follow-up process is established with a structural engineer. This may include drilling in additional reinforcement or some other reinforcement."

Don't wait

What is important, according to Hartmann, is that building owners and building managers become more aware of the risks with concrete consoles. "Money plays a big role. Housing associations are better able to address problems and set up maintenance programs. Homeowners associations sometimes have less financial clout. Don't let that be a reason to wait for the day the national press reports that another balcony has come crashing down."