Ensuring that resilient flooring is installed correctly is a complex process. Factors such as indoor temperature, moisture control issues and even the type of adhesive being used have to be taken into consideration. Naturally, this leads to questions, so I’m opening my mail bag to answer the latest round of installation-related questions from readers.


Q: What is the reason for the increased frequency of trowel notch show-through on resilient sheet installations? And is there a way to prevent this from occurring?

A: Most resilient sheet adhesives manufacturers have gone to a dry-to-touch type adhesive. These adhesives are allowed to dry-to-touch and any imperfection in the adhesive spread is a potential show-through problem. Installers need to be extra cautious when applying the adhesive.

Things like trowel notch spacing and trowel notch depth are extremely important. The need to carry an ample amount of adhesive ahead of the trowel to prevent trowel chatter and small puddles is also a concern. One of the ways to aid in the prevention of this concern is to spread an area and knock down the trowel notches with a short nap paint roller, but this too needs some care so as to not leave any lumps or lines that could show-through.


Q: Is there a way to prevent heat weld scorching from occurring?

A: The addition of lower maintenance finishes has created a need to pay more attention to heat welding equipment, weld tips and temperature settings. The new finishes are more temperature sensitive and will scorch easier than the materials of old that did not have a finish applied. In a lot of cases, the finish will scorch and will not be seen until the material is subjected to maintenance after the scorched area collects dirt.

When installing a new floor, the installer should take a scrap piece of material and test a heat weld to ensure he has the correct temperature setting and speed necessary to complete the weld. Sometimes, changing the tip (to a narrow preheat tip) will solve the problem.


Q: Can you tell me what causes bumps in the concrete following a flooring installation?

A: In certain areas of the country, reactive aggregates get into the concrete mix. These aggregates can be coal, lignite, shale, hard clay and wood. These aggregates, when exposed to moisture in concrete, will expand. This expansion usually occurs after the flooring is installed and the slab goes into equilibrium. Then the reactive aggregate at the surface of the concrete, which is drier, will draw moisture and expand.

When this happens the flooring will have small bumps, looking like the floor was poorly prepared. When you open up the area of the bump it will be difficult to see.  Usually the bump will be about 0.010” to 0.015” and is difficult to feel or see.  Unfortunately, there is no easy to fix the problem.    


Q: Can you explain why saw cuts that were cleaned and filled with floor patching compound prior to installation start to show-through about six weeks after the installation?

A:  The answer is slab curl relaxation. A slab tends to curl while drying. This is due to the fact the concrete slab is wetter on the bottom than on the surface. As a slab dries it will shrink and as the surface shrinks the slab will curl upward. The saw cuts (control joints) are sawn immediately after the slab is poured and are cut to control the cracking of the slab. The saw cut will tend to “V” slightly after the cut is made and the slab starts to dry.  

Throughout the drying process the slab will always be wetter on the bottom than on the surface, maintaining the “V” effect at the saw cut. Once the slab is determined to be dry enough to install resilient floor covering, the saw cut is cleaned out and filled with a good grade of floor patching compound. The slab is next sanded smooth and ready for flooring material installation.

Once installed the new flooring material acts as a topical vapor retarder and allows the slab to equalize in moisture content from top to bottom. This condition is known as equilibrium. Once into equilibrium the slab’s surface expands from the increase of moisture and the curl flattens out.  

During the flattening out process, the “V” saw cut closes up and the patching compound (with nowhere to go) bulges up creating a joint show-through problem. The question remains, “Who’s at fault?” Actually this is a byproduct of fast track construction and lack of indoor temperature controls.


Q: I have had a lot of complaints with chair legs and the lack of proper furniture rests creating indentations as well. Can you give me any assistance in addressing this problem?

A:  There are a lot of chairs that have legs that exacerbate the indentation problem.  The worst offender is the tubular chair leg that only allows a small angular part of the tube to set on the floor. A lot of folding chairs fall into this category and wreak havoc with any resilient flooring. The other factor is the person who leans back in their chair. Once these chairs are tilted back the static load can go into horrendous weighting loads.

The other type of chair is the roller chair. In this situation, the repetitive rolling is causing a shear on the adhesive and with prolonged rolling, especially by someone of large stature, the damage is certain.  


Q: Can you outline the recent changes to ASTM F-1869 and calcium chloride testing on lightweight concrete?

A:  Lightweight concrete (not gypsum concrete) is too porous to be accurately measured via the calcium chloride test method in ASTM F-1869. Actually, neither type concrete is recommended for calcium chloride testing. The recommended test method for lightweight concrete is to use the ASTM F-2170 relative humidity test method.