April 27, 2007

Innovation

Indoor, outdoor environment meet at the flooring

Experts advise reviewing text on standards

DAN O’REILLY

correspondent

More attention needs to be paid to the design, use and testing of slab-on-grade construction, according to a building envelope specialist.

“You’re separating an indoor environment from an outdoor environment,” says David De Rose, project manager with Halsall Associates Ltd. and an Ontario Building Envelope Council director.

While not wanting to get too specific, De Rose said there has been accelerating number of legal cases stemming from flooring failures in the past few years.

Some of the causes include the increased popularity of low cost resilient flooring such as vinyl or linoleum sheeting which has a low vapour permanence that can trap moisture.

Another reason is the manufacture phase out of VOC’s and their replacement with water-based, low VOC-water based adhesives. While this may be a laudable environmental effort, such adhesives are more sensitive to moisture and alkalinity, he says.

Of course, another major reason is construction techniques and practices, especially in this era of fast-track construction where contractors are under pressure to complete the building as fast as possible with the result the concrete isn’t given enough time to dry.

There may also be inadequate ground moisture controls. For more information on this subject, De Rose advises designers to review the American Concrete Institute standards.

Designers, contractors and other professionals may also be working under a false sense of security because of the limitations of industry test standards, he adds. An example is the calcium chloride test, which only detects moisture in the top 0.5 to 0.75 inch of the slab.

“But moisture redistribution can occur throughout slabs that have been covered with low vapour permanence flooring.”

Instead of limiting themselves to one method, industry professionals should use a combination of different moisture testing techniques such as Bond, pH and relative humidity tests.

“Relative humidity-based testing and thresholds are well developed in Europe, but only starting to make their way to North America.”

What other options are open to designers and contractors to avoid disputes?

In order to avoid disputes, designers and contractors may consider avoiding moisture-sensitive flooring adhesives if possible, including manufacturers in the design stage, using compatible leveling materials, paying attention to the concrete mix design and allowing for adequate drying, he says.

“If scheduling is an issue, they can stipulate the use of accelerated drying techniques or topical treatments such as epoxy coating. Put that in the tender. But testing is still required.”

Designers and contractors should also consider using a building envelope specialist. To promote the highest level of building science in the industry, the OBEC created the Building Science Specialist of Ontario (BSSO) designation a few years ago. “We’re still trying to market this (designation) to the industry.”

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