While laying concrete floors on the surface may seem to be one of the simplest construction challenges, Geoff Kinney, executive director of the Concrete Floor Contractors Association (CFCA) figuratively poured cold water on that assumption at a recent presentation to the Ottawa Chapter of Construction Specifications Canada (CSC).
In fact, the class or exposure, ambient temperatures and air contents are among the many variables determining the quality and sustainability of a concrete floor, as documented in a massive set of specifications, standards and guides for architects, engineers, contractors and owners.
Kinney says he expects few people would try to read through the entire 800 page document, CSA A23. 1/2-2019 – Concrete Materials and Methods of Concrete Construction — but there are many points worthy of consideration to prevent common job site problems and to obtain better long term performance.
The superficially simple concrete floor laying process is complicated by the fact that different floors have different uses, and these require varying levels of flatness/smoothness. As well, weather conditions can present real problems, either in the summer heat or winter cold. And there are the challenges of managing and coordinating the proper methods and materials as the concrete must be poured and properly laid out correctly in a short time frame.
Quality problems are a real issue, in part because of divisions of responsibilities and conflicting project demands. Owners are often perceived as only wanting the lowest costs, but they are “eliminating durability to save money,” Kinney said.
Designers, meanwhile, often work on very short schedules, “navigating through confusing materials options, changing standard requirements, and unequal alternatives.”
Finally concrete contractors face the challenge of keeping prices low while dealing with “hostile ambient temperatures, poor site conditions and substandard materials.”
“Divisions of responsibilities are causing problems,” Kinney says. “Lots of different people must come together on the day of each concrete placement to make a good floor.”
There are some solutions to manage these risks, he said. One is to define full responsibility for the floor construction to the concrete floor contractor. There needs to be consistent and immediate inspection of each placement. The additional cost of inspectors to verify CSA compliances is a small price to pay to ensure that the concrete is poured and cured according to specifications, while discouraging short-cuts and promoting better quality and hardened performance.
Kinney also advocated an interdisciplinary pre-construction meeting at least one month before the concrete placement. This allows everyone to review the project specifications and site conditions, to coordinate everything in its proper place.
Unfortunately, he said, longer-range thinking is the exception rather than the rule when it comes to concrete flooring. Contractors often get the call to do their work only a week or two before they are expected to arrive at the job site, making it almost impossible to avoid problems and improve quality. “There’s very little planning time to get involved which is critical to obtain good results.”
“Building floors is really co-ordinating chaos,” he said. “There are 50 items to make a pour right.”
“With value engineering we have found that higher performance materials yield hidden savings based on an analysis of loading conditions.” he said. However, without owner inspections, there is a real risk that the specifications and standard requirements will not be met – it is expensive and difficult to rectify problems after the concrete is hard.
“Take action on sustainability now,” Kinney said. “Specify preconstruction meetings to avoid common problems and inspect everything to improve quality and value.”
And, while there might seem to be an obvious self-interest behind the message, he encouraged owners and specifiers to consider prequalifying CFCA members to help promote “safety, quality and integrity in the concrete floor industry.”