Revisiting a popular format: Installation Q&A

Christopher Capobianco

It has been over a year since I did a Q and A column, and the questions keep coming. So, here are some recent ones that I’ve been asked, or are based on situations that I have run into.

Q: What problems do you see most often in “click” floating floors?
A: This category continues to grow as more products with synthetic cores (WPC, HPC, rigid core, etc.) are entering the market and traditional products with HDF (High Density Fiberboard) core (laminate, cork, etc) are still going strong. From an installation point of view, some of the challenges are the same in both groups.

Failure to allow for expansion in doorways can result in uneven expansion and contraction of “click” floating floors, causing gaps in the joints.

The answer to this question boils down to two issues; expansion and floor flatness. I’ve had to look at a number of different projects in recent years with different click products that had failures. Ignoring the need for expansion space was one of the causes in several cases. My first example was a product with an HDF core that was installed in three rooms and a hallway without any expansion joints being allowed. As a result, the floor was gapping in several areas. The installer repaired it by taking up portions of the floor, adding an expansion joint with a T molding and reinstalling the material. A carton or two of new material was needed because the tongue of the “click” tongue in groove joint had broken.

In another case, an HDF floating plank floor was installed in a large commercial space, with a large cabinet on one side of the room and a soft drink machine on the other; both on top of the finished floor. There were a number of gaps in the end joints because these heavy pieces created “pinch points” that did not allow the floor to float. The way to avoid this would be to install the cabinet before the flooring, and to isolate the area where the machine was by adding an expansion joint with a “T Molding.” They wound up doing it after the fact, which was a lot more difficult. One more example in the opposite direction is the failure to allow for expansion space against walls, which I’ve seen in synthetic core products and HDF core products.

When material is installed tight to a wall or other fixed object, “tenting” can occur at the joints on the sides or the ends, because the floor has nowhere to move when expansion occurs, so it lifts at the joints. The most extreme case was an installation where the HDF floor was had buckled over a two-foot-long area, as if there was a beach ball beneath the floor. Miraculously, the click joints held tight, and the installers were able to take the floor apart, add an expansion joint, and re-install the material.

Failure to allow for perimeter expansion can cause side joints to “tent.” In this case, screws were used as an emergency repair measure.

HDF core products have been on the market for decades, and one would think that it’s common knowledge to allow for expansion, not only around the perimeter, but also in doorways and over long runs over 35 or 40 feet. I guess it’s not co common knowledge after all. On the other hand, synthetic core products are often sold as not needing expansion space. This may be true in doorways and over some longer runs, but perimeter expansion is usually recommended, so don’t assume you can install tight to a wall. Very long runs in areas like a corridor or other large commercial space may need expansion in the field area in addition to the perimeter. I’ve seen failures of synthetic core products in both examples, so don’t make the assumption that these materials don’t require expansion. Check with the manufacturer’s technical department to be sure.

With regard to floor flatness, this has become a problem in a lot of cases. The assumption that “floating floors can install over anything” is getting a lot of people in trouble. Sure, floor smoothness is not as critical as it is with a glue down floor, but floor flatness is even more important. If there is any kind of a dip in the floor, it creates a hollow area that allows the material to move up and down. Over time, the tongue can weaken and break, causing gapping. It’s important to check the floor flatness before installing a floating product. Use a long metal straight edge, a laser, or other method to make sure there are no dips in the floor.

Q: (From an architect) I’m considering using (glue-down vinyl) plank flooring in a residential basement. If we install on an existing slab, should we do some kind of vapour barrier on top of the slab to make sure we don’t have moisture migration?
A: I have been writing on this subject for decades, so I’m always glad when someone thinks to ask this question. I’ve seen more moisture related failures than I can remember and volunteered to help write industry standards for how to test and why.

However, making assumptions like “the concrete looks dry… feels dry…smells dry” continues to get people in trouble and failures are still happening. On top of that, as I said in my July column, the term “waterproof” is being misused so much in our industry that moisture emissions are being overlooked. My answer to the architect was a simple one: The need for moisture mitigation will depend on the moisture levels. It’s the same rules for any floor covering you’d install. There is an industry standard, ASTM F710 (Standard Practice for Preparing Concrete Floors to Receive Resilient Flooring) that says, “All concrete slabs shall be tested for moisture regardless of age or grade level.“ The best test is the relative humidity (RH) method, ASTM F2170, that measures moisture inside the slab. A lot of flooring contractors do this test regularly so you should include that in your specifications. If the results are within the manufacturer guidelines, then the job can proceed and if not, a mitigation coating can be applied.
To my readers that are not yet versed in concrete moisture testing, there is no time like the present. RH testing is important to do and there are kits available that make it easy.

Q: (From an installer) We removed a VCT floor and scraped the black adhesive residue, so the concrete floor is smooth. Can we glue down the new carpet tile right over this?
A: I am always nervous when new adhesive goes over old adhesive, because chemical reactions can occur that make the new adhesive fail. Luckily, there are some great primers, patching and leveling compounds on the market today that can go over many types of adhesive residue and provide a good substrate for the new floor covering.

Using an acrylic latex adhesive over a black “cutback” adhesive caused a failure in this LVT floor.

Be careful, however, because if the residue is a water-based adhesive, total removal may be necessary. Check with the preparation products manufacturer to be sure. In this case, there was a “skimcoat” product available to go over the black adhesive residue so that took care of the situation. Yes, it was an extra step that added cost to the job, but it’s a good bit of insurance to be sure that the new floor covering is well bonded and stays that way.

So many questions and so little time… If you have any questions of your own, please drop us a line here at Coverings! I’d enjoy some direct Q&A with our readers!

Christopher Capobianco has been in the floor covering industry since the 1970s in various roles including retail and commercial sales, technical support, consulting, journalism, education and volunteer work. He currently is part of the sales team for Spartan Surfaces in New York City. You can reach him via [email protected].

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