The mailbag just can't seem to stay closed in Ray Thompson's workshop. Following up on the success of his last Q&A endeavor, Thompson takes a look at questions aimed specifically at the commercial marketplace.

In the March/April issue of FCI, I opened the mailbag and answered ten of the more pressing questions regarding resilient flooring. Faced with an overwhelmingly positive response to that article, I thought it would be a good idea to put the same focus on commercial applications. Can you give me any tips on seaming linoleum?

Linoleum is a lot different to seam than sheet vinyl. Linoleum tends to shrink in length and grow in width. Seams should be cut slightly open on side seams and not on cross (end) seams. What are your thoughts on applying a tile adhesive over an existing cutback adhesive?

It depends on the circumstance. A cutback adhesive that is active (not scaly or poorly bonded) can be scraped down to a thin residue, and a clear thin-spread can be applied directly over the residue. Do not apply a cutback adhesive over a cutback adhesive, as they tend to create excess and will bleed. Beware: some old cutback adhesives contain asbestos. What are your thoughts upon applying latex adhesive over an existing latex adhesive?

There is a risk involved with applying an adhesive over an existing adhesive. Old latex adhesives were high in solvents and low in processing oils. The newer adhesives that meet VOC (Volatile Organic Compound) regulations are low in solvents and high in processing oils. In certain circumstances, when a new adhesive is applied over an existing latex adhesive, the oils are leached out of the new adhesive by the old, oil-starved adhesive. This causes the new adhesive to crystallize and become chalky and scaly, and consequently it will lose its ability to hold the material. Why does the heat-welded seam in linoleum appear weaker when compared to a vinyl seam?

The weld of a vinyl seam is a fusion between the vinyl in the material and the vinyl in the weld rod. In the case of linoleum, there is a bond by the rod rather than a fusion. This is why a linoleum heat weld is weaker than a vinyl heat weld. When laying VCT tile, I have instances where the tile tends to run. Can you tell me what causes this?

There are three basic causes to tile running:

  • The flatness of the substrate. The more undulation there is in the surface of the floor, the more the tendency for the tile to run.
  • The installer needs to be aware of the tile joints during the installation by keeping the opposing corners aligned. Installers may pull the tile during the installation because they hold it by the corner, twisting and moving it out of alignment. The tendency is for a right-handed installer, holding the tile by the right corner, to pull the right side of the tile in tighter than the left side. A tile needs to be held in the center.
  • The tile is out of square. It has been my experience that tile is rarely out of square, but often gets the blame for the above two reasons. What causes cementitious patching compounds to lose their compressive strength?

    There are two major factors that affect the strength of cementitious patching compounds:

  • Drying too fast. Cementitious patching compounds need to be allowed to develop naturally. This allows for the cement to completely develop its cohesiveness. This can be aided by dampening the surface to be smoothed. This will stop the substrate from absorbing the moisture in the mix, allowing it to develop its cohesiveness.
  • Mixed with too much water. Water is non-compressive and, when mixed in excess, will force the cement molecules apart, resulting in a poor bond. What are the major factors in successfully completing a vapor emissions test (VET)? There are four factors that have a major influence upon the results of a vapor emissions test:
  • Cleaning the concrete surface. All residues must be removed to open the concrete surface, allowing nothing to retard the moisture vapor movement and create test results that are below normal.
  • Temperature. The temperature must be close to that of the finished environment. The ASTM F-1869 states 70 degrees Fahrenheit (plus or minus 10 degrees).
  • Humidity. The humidity needs to be as close as the finished environment. The ASTM F-1869 states 50% humidity (plus or minus10%).
  • Exposure. The anhydrous calcium chloride crystals need to be exposed between 60 and 72 hours. The ideal is 63 hours. What are the factors that lead to underlayment joints showing through the finished flooring material? There are several factors the cause the underlayment joint to telegraph through the newly installed floor:
  • Acclimation of the underlayment allows it to either gain or lose moisture content, and adjusts the underlayment dimensionally.
  • Moisture migration from the area below the suspended floor.
  • Improper fastening of the underlayment joints. The spacing is too far apart or too far from the edge.
  • Improper fasteners used to fasten the joints. Many installers believe that staples hold better than ring-shank nails, and that pneumatic-driven fasteners hold better than conventional fastening. Not true.
  • Improper filling of the underlayment joints. Over-watering of the patching compound, allowing it to dry too fast, or adding too much water to the underlayment by mixing the patch directly on the underlayment all contribute to this problem.
  • The underlayment joints are not offset far enough from the subfloor joints. I think there needs to be a minimum of 6 to 8 inches of offset. The offset should be enough to allow two rows of fasteners before they reach the subfloor joint. Should a new installation of VCT tile be stripped or sealed after the installation? A newly installed VCT tile should be sealed. The tile should be allowed to set for about five days prior to the start of any maintenance procedures. The tile should then be cleaned thoroughly and given a coat of floor sealer. A floor sealer is a high-alkaline resistant floor polish, and will help prevent future stripping from affecting the adhesive at the tile joints. The use of strippers, which are high in alkalinity, opens the possibility of attacks on the adhesive by way of migration down between the tile joints, especially if the adhesive has not completely cured. There seems to be a lot of manufacturers of moisture treatments for wet concrete slabs. What are your thoughts regarding the use of these products? Moisture remediation treatments have grown in popularity for several reasons: The concrete was not specified properly; the concrete was over-watered; or the concrete was not cured properly. Whenever there is a non-conformance, there is a fix. It is generally expensive and not budgeted for. There are many treatments available; some are penetrating, while others are coatings. Some work well while others fail. One sure test is to complete a series of moisture emissions tests to determine the success or failure of the treatment.