|Particularly in the 1970s and 1980s, many buildings in Calgary were built with post-tension cable construction in one or more of the horizontal concrete slabs. Some buildings being constructed today use this method as well.|
This construction method uses steel strands inside a plastic tubing with grease or oil as a corrosion retardant. There are many strands in both directions cast within a concrete slab, with the strands tensioned against the concrete at the ends of the slab. Sometimes you can see the plugs on the end of a slab that conceal the tensioned end of a cable. The purpose is to create a slab that can support more weight without additional columns that consume space, and also to minimize cracking in the slab.
The concern about a post-tension system relates to the potential for corrosion and deterioration of the steel cables if water and oxygen has entered through a crack. If sufficient cables have deteriorated and lost tension, they may have reduced the slab's ability to support weight, and may require costly replacement. Post-tensioned slabs also require a certain amount of preventative maintenance in the form of waterproofing any portions of the slab that are exposed to the elements. The waterproofing is another maintenance expense to the Corporation.
If the Corporation has been regularly having their post-tension system monitored by an engineering firm, and have been performing the maintenance as recommended by that firm, the building is no riskier than any other form of construction. However, the Corporation does need to set aside some funds in their reserve account to accommodate the possibility of a future expense.
Check your documents for a recent post-tension report.
The document package you receive from the seller of the unit should include a recent post-tension report if the building has used that construction method. The engineer's comments will give you some insight into the condition of the system, and the likelihood of future problems. Many engineering firms also give a recommendation for what funding the Corporation may require in the future.
The financials will show whether the Corporation is setting aside money for post-tension work.
The operating budget shows if they are allotting an amount for annual post-tension inspections. You may find mention of post-tension work having been done recently in the audited financial statements. Their reserve fund study will reveal if any funding for post-tension work was recommended to the Corporation. And their reserve fund study plan will state if some of the funding is earmarked for possible post-tension work.
Researched from "Are post-tension buildings too scary?"
by Phyllis Fyckes, Calgary Real Estate News, Vol. 21 No. 50 | December 11, 2003