Contributed by Eric D. Lussier
You can never start a conversation early enough in construction. Why is it that we wait so long to have that difficult talk? This isn't the birds and the bees with a pre-teen. This is real world ramifications that can affect many on a project.
We' are working on a flooring replacement project that we bid in April of 2018. This project has been on the verge of installation since September. We go over and above to ensure that our proposal is very clear at the time of the bid: What we will do, what we won't do and what is the responsibility of others.
It's important to note that any flooring contractor is not the Clark Kent of a renovation project. More importantly, we are not Clark Kent's alter ego, Superman, on a project. Meaning, we don't have x-ray vision. Conditions underneath existing flooring are unknown to all until the existing flooring and adhesive is removed and the base slab is 100% visible. You could have unexpected layers of flooring or adhesives, hazardous materials such as asbestos, mercury or lead, excessive concrete cracking, delaminating patching or high concrete moisture. Since we've seen each and every one of these unforeseen instances in the past, we exclude any and all subfloor preparation.
If you are preparing construction documents or readying for a flooring project yourself and you have a certain end result in mind and it needs to be included as part of the base bid contract, you need to be very exact and precise with wording. The end result should be so clear in your documents that a layman can understand the proposed scope of work.
On this particular project, the scope of work included flooring removal and to provide the following:
What's wrong with that scope? From a flooring contractor's perspective, I offer you the following response on each line item.
Contributed by Eric D. Lussier
I sat through a pre-construction meeting via conference call today to go over the ins and outs of our upcoming flooring installation. This project will be a combination of a renovated facility, with a new addition being constructed. We have a scope within each section, installing two dance floors in the renovated side and installing 5,000 square feet of gym flooring in the new construction.
After we were asked to review our approximate duration on site to complete our work, we were addressed with the question "how long after the slab pour can you be installing your floor? Is two weeks enough?" At first, I thought I didn't hear the general contractor right, so I didn't put much emphasis on it. But then it was posed again. The project was behind schedule, they still wanted to be completed in May and they wanted to know how soon after the slab was poured could we be in there installing the floor.
First, let me just say that we are supposed to utilize an on-slab vapor barrier as part of our synthetic gym flooring system that allows us to install up to 100% relative humidity in the concrete slab. But, but, but...two weeks after the pour? Were we really being asked that? We're going to be putting a non-breathing system on essentially a brand-new slab and then expect it to behave in a predictable manor?
Secondly, how legitimate is this actual request? All other trade work needs to be done before the flooring actually goes in. Not only does that include the HVAC system, lighting and basketball hoops, among others, but they'll all be done within those two weeks?
For the record, our flooring's installation instructions ask that "the concrete subfloor will be cured for a minimum of at least sixty (60) days.” That would put us well beyond the proposed opening date for the school. Fortunately, we can offer a two-part epoxy moisture mitigation system, which can be utilized with the only parameters being “Newly prepared concrete must be cured for 7 days”.
We addressed our timelines and concerns and wrapped up our conference call after the Owner stated his position to the General Contractor on the importance of the schedule being met. He stated that our call should have been held months ago to state that the flooring couldn't go in during such a short window after placement. But was it really necessary to tell them this months ago? Is it not common knowledge what a typical new construction duration is?
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 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 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.
Let's Fix Construction is an avenue to offer creative solutions, separate myths from facts and erase misconceptions about the architecture, engineering and construction (AEC) industry.
Get blog post notifications here