Surface Solutions

As you know, excessive moisture is the biggest single cause of failure in contemporary flooring installations according to the CFA. Recent calls to the Altro Technical Hotline have certainly involved some interesting examples, from which I hope you can learn.

In the first case a surface damp proof membrane (DPM) had been used and the moisture level leading to the failure did not exceed the parameters stipulated for the type of product.  So what went wrong? 

The installation was in a ground floor hotel kitchen. A standard vinyl sheet had been installed with disastrous results, but it became difficult to find time to close the kitchen down to redo the floor. During recent refurbishment, new PVC safety flooring was installed. The contractor removed the existing vinyl and applied a latex smoothing compound. Because he was worried about residual moisture and there was no integral DPM, he applied one to the cured latex and laid the flooring in a two part urethane.

The job looked great for about a month; then the problems started.  All the heavily trafficked areas started to lift, although the welded joints were still intact and there were no breaks in the safety flooring. When the contractor returned to site following a complaint and removed a section of flooring for closer inspection he found that the whole system had failed and called us to see if we had any ideas.

The reason for the failure was that when he removed the old vinyl, he left the adhesive in place and screeded over it. Most standard flooring adhesives are moisture soluble and the one in question was no exception. So, once the surface DPM and flooring were installed, any moisture from the subfloor would emulsify the residue of existing water soluble adhesive, thus releasing the system above.

The second situation is quite common and we probably deal with one or two such cases a month. This job was a school corridor with concrete floors, built in the early 1960s with 9” thermoplastic tiles laid in asphalt tile adhesive throughout. The specification was to uplift the tiles, latex over the existing adhesive then install new sheet vinyl flooring in approved adhesive, which in this case meant acrylic.

The job was completed during the summer holidays but by October was blistering badly and becoming a trip hazard.  According to the contractor the sheet can be lifted from the floor and there are obvious signs of excessive moisture. However, the headmistress says there has never been a problem with moisture since 1973. Both of them are right.

The building was constructed before the days of integral DPMs and the solvent/ bitumen based asphalt tile adhesive (ATA) was incredibly resistant to residual and subfloor moisture. Thermoplastic tiles allow any moisture beneath to permeate via the joints preventing build up of moisture becoming detrimental to the integrity of the flooring system.

So in this case the answer was simple. With the removal of the old ATA system, moisture from the subfloor unable to escape through the new vinyl sheet was trapped and attacked the new moisture sensitive adhesive causing it to release the new flooring and lead to the failure.

This article first appeared in the March 2007 edition of the CFJ.