You’ve probably heard of rebar—the steel reinforcement bars commonly used in concrete construction—but have you heard of post-tensioning? It’s another way to strengthen concrete, but it uses steel strands or cables instead of bars.
Because it allows developers to build thinner (but stronger and more reliable) concrete slabs, it’s commonly used in office buildings and condominiums, where thinner floors are more attractive. Post-tensioned construction makes it possible to retain comfortable ceiling heights while reducing total building height and weight load.
Conventional rebar keeps concrete slabs intact after cracking, but post-tension tendons provide ongoing structural integrity to the building. Unfortunately, they can still be susceptible to wear and occasionally require repair.
If you’re looking at a potential condo to buy, keep an eye out for the following potential signs of structural post-tensioning system distress:
- Broken strands coming out of the structure
- End anchorage lifted out of the concrete
- Cracking concrete running parallel to the strands
- Excessive deflections
- Punching shear cracks in slabs
- Diagonal shear/flexure cracks in beams and joists
If you already own a condo, check with your association to see if your building uses post-tensioning. If so, make sure you have your building inspected regularly to catch problems in the early stages. Regular inspections will give you peace of mind and will keep repair costs down.