Contributed by Chris Maskell
Is there a problem with flooring glued to concrete with a high fly ash content? Fly ash is the finely divided residue that results from the combustion of ground or powdered coal and that is transported by flue gasses. It is used as a replacement for Portland cement in concrete and in some cases can add to the final strength, increase its chemical resistance and durability and can significantly improve the workability of concrete.
If you talk to enough flooring professionals on the subject of site preparation and related issues, eventually the question of concrete, high fly ash content and adhesive bond failure will crop up.
I've heard the question from all corners of the commercial flooring industry, and there are many concerns, but few definitive answers. As a result, many commercial flooring contractors are not warrantying their installations over such concrete. Instead, they add a disclaimer in their 'terms and conditions’ stating that no installation warranty is offered when a certain percentage level of fly ash in the concrete mix is exceeded. Some say 15%, others 20 to 25%, some say more. Such disclaimers won't protect the flooring contractor if there is a failure and things turn nasty.
Concrete with a high fly ash content results in a denser, less porous product. This in turn can interfere with the flooring adhesive’s (or hydraulic cement underlayment's) ability to mechanically bond. Hard troweling of the concrete surface to a super smooth finish adds to the problem, and introduces the need for shot blasting. Shot blasting requires time and money, both of which are in short supply at the end of the project when the flooring is scheduled.
As concrete mixes are proprietary to the concrete supplier, it can be difficult to confirm exactly how much fly ash is present in any one mix. If this is the case or where the concrete is super smooth, unusual in color, or if you are just not sure, then perform a water absorbency test in accordance with ASTM F-3191 and/or a bond test prior to installation.
Place dime sized droplets of water on the cleaned concrete surface, if they are not absorbed after 60 seconds (or in accordance with ASTM F-3191), you could be facing an adhesive bond issue. If this is the case then you need to shot blast to a concrete surface profile (CSP) of 1 or 2, or per adhesive manufacturers’ requirements depending on the floor covering to be installed. (A CSP 2 for example, is similar to 60 grit sandpaper)
Contributed by Liz O'Sullivan
(Editor's Note: It should be noted that the skilled trades gap has been a long time coming, and this post was originally written by Liz over seven years ago on her blog that you can find here)
I have great respect for people who work hard and are good at their work.
Many people consider hard work and skill to be respect-worthy. However, the same people who respect hard-working and successful doctors, actors, and software engineers, often have little or no respect for hard-working, successful construction tradespeople.
This lack of respect may partially stem from a lack of understanding of what is involved in the work of tradespeople. Sometimes we do a little fix-it work around our own homes and figure that it’s not that hard. We watch tradespeople on TV who make their work look easy, and think, “Oh, well I could do that.” But it actually only looks easy, and that’s because they know what they’re doing!
I suspect that there’s actually a deeper and broader pattern of thinking that’s at work here, and it needs to change, soon.
There is a lack of respect for the construction trades because of the push by schools to get kids to college. Somehow, attaining a 4-year college degree has become the only respected post-high-school option for many kids. It may be the only avenue they hear about from their guidance counselors and parents.
In the Denver Post on February 20, 2011, a guest writer, high school teacher Michael Mazenko wrote:
“…schools keep pushing the college-for-all mentality. The education system should promote the trades and skilled labor as much as it does academics and bachelor’s degrees, and education at all levels should become more experiential and skill-based.”
“This conclusion is supported by the recently released Harvard study that concluded not all kids should go to college – or at least not a four-year university in pursuit of a bachelor’s degree. The aptly titled report ‘Pathways to Prosperity’ recommends a new direction for education reform, based on the practical needs of students and the economy.”
Not every teenager really wants to have a career that requires a 4-year-college diploma. But there is pressure from society to go get that college diploma, or else he may be considered to be not smart, or to be an underachiever. Sometimes it works out, and the college student thrives, and ends up taking a career path that did require that college degree. Sometimes it doesn’t work out, the student struggles or hates college, or just wonders why he’s there, AND has student loan debt to deal with after the inevitable drop out of college.
Contributed by Chris Maskell
The flooring industry is constantly challenged by the same repeating issues. Installing too early, wet concrete, non-flat sub-floors, sub-floor surface not prepared, heat not on, windows not in and lack of installer training and certification. In fact, as construction speeds up to meet demands for faster build times and with the threat of an increase in the cost of borrowing money lurking in the economic wings, the provision of acceptable conditions for the flooring contractor is becoming less likely.
This raises the importance of supporting those in the construction team (Building Owner, Construction Manager, General Contractor, Design Authority, and Flooring Contractor) with good, timely information that helps all involved plan ahead for the floor covering installation. As one of the last significant trades onsite, the flooring contractor needs certain conditions, that if not planned for in advance, will be next to impossible for the Construction Manager/General Contractor to provide without extra time and/or extra money: two things in short supply at the end of a build or renovation.
Change is possible, but requires a few things to be understood and acted on in advance.
There is a generic Canadian floor covering industry reference manual available for specification, which supports all construction parties, and when included in the Division 09 section of the construction documents, means correct flooring processes and supportive language is available to guide the floor installation and all the points listed below.
Contributed by Laverne Dalgleish and Roy Schauffele
In the last few years, a lot of attention has been placed on the proper installation of continuous insulation in buildings (editor: As per EnergyCodes.gov, continuous insulation is defined as insulation that runs continuously over structural members and is free of significant thermal bridging; such as rigid foam insulation above the ceiling deck. It is installed on the interior, exterior, or is integral to any opaque surface of the building envelope). The purported reason for this has been to stop the thermal bridging that occurs when you put thermal insulation between steel studs.
Years ago, we started out insulating our buildings by requiring a certain R-Value insulation to be installed in the cavities. In those days, wood framing was very common. As we moved to steel studs in commercial buildings, we realized that the building assembly was performing less than the R-Value of the insulation. From that, we started requiring an “effective thermal insulating value”.
Today some building codes simply require a maximum U-Value for the building envelope, which is supposed to reflect the thermal performance of the building assembly. But does it? In most cases, the answer is “not really”.
When we look at the requirements in the International Building Code and in ASHRAE 90.1, the basic principal of overall building assembly U-Value is there, but the only requirement is that you take into consideration the primary framing members (in a lot of cases, simply the studs). This is a good first step.
If we want to get to truly energy efficient buildings, we need to look at all thermal bridging materials that are incorporated into the building assembly. Not only should the main structural beams be calculated and the steel studs, but we need to look at all thermal bridges. This includes Z channels, fasteners, brick ledges, hat channels, masonry ties, balconies, parapets and anything else that will transfer heat. But the codes are not yet there.
Peering in to the future, there are some manufacturers that are starting to develop thermal break materials, and designers are starting to incorporate thermal breaks into their building envelope design. This is a desire by forward-thinking architects.
Today, the International Building Code and ASHRAE 90.1 do not require you to take all of the thermal breaks into consideration and you do not have to include them in your modeling. The Z channel is a common method used to be able to structurally support the cladding system. Is it a thermal break? Yes. For code purposes, do you need to consider it? No. That is a disconnect between code requirements and good building practice.
We want to reduce the energy use by our buildings and the building envelope provides the biggest opportunity. We need to bridge the thermal gap between what is required by the codes and what is good building practice. Having requirements for continuous insulation was a good step forward. We need to keep going.
This article was originally published by the Air Barrier Association of America under the title 'How Continuous is Continuous? And what about Z channels?' and a PDF may be downloaded here.
Contributed by Jason Spangler
For years now, the in situ relative humidity (RH) test for measuring the moisture condition of concrete has been shown to be the most reliable, accurate test available.
As far back as the 1960s, laboratories at the Portland Cement Association conducted controlled tests that verified the accuracy of RH testing. This research was followed by years of additional testing at Lund University in Sweden and elsewhere. In 2002, ASTM International first established the F2170 standard for conducting RH tests on concrete slabs.
The research confirmed two key discoveries:
Other methods typically involve taking measurements only at the surface of the slab. As the research has found, a surface-based moisture test can’t provide an accurate measure of a slab’s true moisture condition. That’s because it doesn’t account for the moisture conditions deeper within the slab, and those conditions are typically quite different than conditions at the surface.
The Standard Evolves as the Science Tells Us More
The initial ASTM F2170 for in situ RH testing was established in 2002, after continuing research at Scandinavian universities in the 1990s identified the exact specifications for conducting a reliably accurate RH test—placing the test probe at 40 percent depth for slabs poured on grade or 20 percent for slabs drying from both sides. After these scientifically-validated specifications were firmly established, ASTM International published a usable standard.
Until now, the ASTM F2170 standard has required a 72-hour waiting period between drilling the test holes where the RH probes are placed and taking official RH measurements. In practice, readings are often taken before the 72 hours has passed, so contractors have an idea of how things are trending. But because the official readings couldn’t be taken before 72 hours, that meant all decisions and work were basically on hold for those three days. Full stop.
Yet we’ve seen how the research on the RH test method has helped to refine our understanding of how best to use it. This trend continues. In 2014, a Precision and Bias (P&B) study, commissioned by the ASTM committee, tested for differences in RH readings at various intervals within the 72-hour period. In part, the idea was to assess if it is actually necessary to wait the full 72 hours for an accurate, actionable moisture readings.
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