Question #1I have had several condominium projects where the concrete was cracked. Our installers filled the cracks with a Portland-based patching compound and installed the sheet vinyl. Shortly after the installation, the once-smooth substrate revealed all of the filled cracks. What caused the cracks to push the filler up, creating a show-through condition?

Answer: One possible cause is no heat in the structure. This will cause expansion and contraction of the slab. For example, a 5º F increase in the slab temperature will cause the slab to move approximately 1/8-inch per 100 lineal feet. Installing flooring material when the slab has not been stabilized is just asking for this type of problem.

Question #2 How can you check concrete for porosity?

Answer: There are many instances when the concrete porosity must be tested. This is especially true when installing a vinyl back or non-porous backed material with a water-based adhesive. The best way to test the concrete is to take some clear, clean water and broadcast it onto the surface of the concrete with the tips of your fingers. This will leave small droplets on the concrete. Watch the droplets for about 10 minutes; if the droplets bead up, the concrete is non-porous. If the droplets are absorbed into the concrete, and create a damp spot that disappears into the concrete, the concrete is porous and water-based adhesives will set up.

Question #3 We had a VCT installation fail due to what appears to be a moisture problem. When we did the moisture tests, the calcium chloride tests were all in the 3.5-5.0 range. What would have caused the floor to fail?

Answer: Let’s assume the moisture emissions tests were done correctly. This means the test criterion was done as follows: 1)Temperature: 70ºF- ±10º. 2)Humidity: 50%-±10%. 3)The concrete was cleaned to bare concrete. 4)The tests were weighed within one hour prior to setting and after removal. 5)The dome was sealed through the duration of the test. 6)The test duration was between 60 and 72 hours.

If those guidelines were followed, you would have to take a serious look at the alkalinity of the concrete to determine if it was the cause of the failure. It should be a pH of 9.0 or less.

Question #4 Is there a correlation between the moisture reading on a moisture meter and the results of a calcium chloride test?

Answer: No. A moisture meter will tell how much moisture there is in a concrete slab, either percent by volume, or percent of relative humidity. A calcium chloride test will give you the amount of moisture vapor movement. A high moisture content doesn’t necessarily mean high moisture movement. It is high moisture vapor emissions (movement) that creates the problems that confront the flooring industry.

Question #5 I was told that there is a saw that is used to double-cut seams in commercial sheet vinyl. Do you know of such a device?

Answer: Yes, there is such a device used in the early 70s. It’s a modified Skil saw with a vacuum attachment for double-cutting commercial heavy-gauge sheet vinyl. There are a lot of these saws at the older commercial flooring installation shops. While rarely used, they can be modified to work on today’s materials. The difficulty is in finding replacement blades for the saws.

Question #6 Will old residues of adhesive cause discoloration of new resilient sheet flooring?

Answer: Yes. It will rarely discolor a felt-backed material, but it is possible. Vinyl-backed materials are much more susceptible to discoloration from old adhesive residue. Old resin-based adhesives like those used prior to multi-purpose adhesives, some old latex carpet adhesives, and any adhesive that is oil soluble are suspect adhesives to discolor vinyl flooring. What happens is the plasticizer (oil) in the vinyl will re-activate the adhesive. The re-activated adhesive will discolor the plasticizer, and as the plasticizer cycles through the material, it brings the discoloration to the surface.

Question #7 In flash-coving sheet vinyl, what causes the cracking to occur at the juncture of the floor and wall, where the cove stick is used?

Answer: There are two possible answers to this. It is possible that the cove stick is not secured, or that there is a gap between the floor and the wall bigger than the cove stick, allowing it to slide back under the wallboard. Second is the possibility that when the flooring material was fit into the cove stick, it was not fit tight enough, leaving a gap between the material and the cove stick. Installers must be sure to fit the material firmly into the cove stick, as it is a labor-intensive repair.

Question #8 Why does linoleum appear to have a yellowish cast on it when first taken out of the roll?

Answer: When linoleum is in its final curing stages of production, it is hung in ovens (drying rooms) for several weeks. During this process, a yellowish film may develop on the surface of the product. This film is common on all linoleum products, and is part of the normal curing process of the linseed oil found in the product. This yellowing goes by several different terms: “stove yellowing,” “seasoning bloom,” “drying room film.” These describe the same phenomenon that affects all linoleum. This yellowing will disappear; depending upon the amount of natural light, it can be gone in a few hours to a few days. This is why it is common for the new material not to match the old sample.

Question #9 We had a seam that got dirty prior to the application of the seam treatment. What is the best method to remove the soil that got tracked down into the seam?

Answer: First, take the backside of a knife blade, or something that has flat edge, and try to remove as much of the soil as possible. Next, take a toothbrush and some white toothpaste and scrub the remainder of the soil out. Toothpaste is a mild abrasive cleaner, and will do a good job. Avoid any solvents that may drive the soil into the material or destroy the adhesive. Be sure to clean the seam thoroughly with a clean, wet, white rag.

Question #10 What is the best type of integral (flash-coved) corner to use on a commercial installation of non-patterned sheet vinyl? Wrapped (v-plug) or mitered (boot)?

Answer: Personally, I prefer the wrapped corner. I think it is easier to put-on, it will take more abuse from buffer machines and everyday use, it stays on better than a mitered corner, and there is no seam on the floor.