Contributed by Roy Schauffele
Late fall and during all winter, concerns and problems arise with air barrier applications on CMU (Concrete Masonry Unit). I know because I get the phone calls. Generally speaking, the fluid applied water-based vapor permeable air barriers go on OK but take a long time to cure or set.
Additionally, I’ve observed a myriad of job site problems with self-adhered vapor impermeable sheets, flashings and tapes. The vapor impermeable materials were applied properly but exhibited blistering and lack of adhesion within days. When investigated there was always liquid water on the adhered side of these sheets.
Observations of quite a few jobs leads me to state that, in this investigation, the vast majority of “problem” jobs had the following in common:
OK, let’s deal with what will lead to an excellent new construction air barrier installation and long-term performance:
1. If the Architect/Specifier has specified a dry water repellent in the CMU, it is already causing a potential problem with the adhesion of a water-based air barrier or primer. This issue has been written about previously in an article in Coatings Pro Magazine July 2018 “Legacy Specifications, Wall and Air Barrier Performance”. The Air Barrier installer absolutely needs to make the Architect/Specifier aware of this prior to bid.
2. If the project is wide open with doors, bay doors and windows not finished or openings not protected from water entry, then a tremendous amount of water can enter the CMU causing some of the problems referenced above. The top of the walls and window openings should be treated in such a way as to prevent water from running in to these open areas.
One of my friends and great technical writer in Austin, TX, Mr. Dave Watts, RA, has the following statement in his specifications: Section 04 20 00, 3.18 PROTECTION OF FINISHED WORK, 3.18.e “Protect tops of masonry with waterproof coverings secured in place without damaging masonry. Provide coverings where masonry is exposed to weather when work is not in progress.”
Remember my post from February, entitled 'Project Compaction: Not Just for Soil'? Well, if you don't remember, didn't have the chance to read it, or would like a refresher, I'll give you a few minutes to jump over there and give it a read.
So, guess what? They're not quite ready yet. How close to not ready? Well, the picture above is from this past Friday, the seventh of June. On a project that was supposed to install in May.
As a reminder, my company installs flooring. Flooring is a product that's supposed to go under that pallet of block, the forklift, those 55-gallon drums of something and the tons of miscellaneous equipment, dirt and debris that litters the gymnasium. If I've learning anything over my thirteen years of installations, its if you give someone a 5,000 square foot (or larger) space on a construction site, it will be used as a catch all for everything that doesn't fit somewhere else on a job. Kind of like that junk drawer that we all have in our house.
Please forgive me for my sarcastic tone, but this isn't the first time I've seen site conditions like this, which was three mere days before we were due to start work. And, it certainly will not be the last time.
I tried to be optimistic about their timeline request months ago. In early May, the basketball hoops were due to be installed "by Tuesday next". As of Friday, they're still not. So, along with my company, that's at least one other vendor who was given a commitment date that wasn't adhered to. I'm presuming there's at least a few others.
So, despite our numerous written notices that "it is imperative that we are immediately notified if you will not be ready for the week of June 10th", our requests were ignored. Our last written communication has now gone unanswered for over two business days. And do you know how this will most likely shake out? Chances are we'll be given a very short notice that the site is "now ready" and we'll be expected to drop everything, juggle our schedule and refocus our attention on someone that was unable to be realistic about a project schedule for months.
Buckle up and stay tuned for my next article focused around life as a finish trade.
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.
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)
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.
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