It is essential that all substrates, regardless of type, be structurally sound, rigid, smooth, flat, clean, and permanently dry. The substrate surface must be free of all contaminants or foreign materials such as dust, wax, marker paint, grease, oils, solvents, curing and hardening compounds, sealers, and existing adhesives.
Always carefully read and follow the instructions on the adhesive label regarding the use and application of the adhesive, and always review and follow safety and health warnings included on the label and MSDS.
Requirements of a flooring adhesive:
• Good initial grab
• Reasonable open time
• Excellent final bond strength
• Compatibility with subfloor and floor finish
• Ease of application
• Resistance to chemicals and water
• Non-migratory properties
• Low toxicity
• Low fire risk and cost
Note: The speed of drying of an adhesive will be affected by its formulation, the temperature of the air and the subfloor, the quantity applied and the porosity of the subfloor. The floor installer must be alert to factors which will affect the average open time stated by the adhesive manufacturer.
The trowel is quite a sophisticated metering instrument, the notch spacing and depth controlling the amount of adhesive applied. If you don’t maintain the instrument, you will get an incorrect application and a risk of floor failure.
Adhesive manufacturers always recommend the trowel notchings to be used to give the right spread of their adhesive. Spreading on concrete or cement subfloors will cause trowels to wear down causing too little adhesive to be spread, with the risk of an expensive floor failure. Not only will too little adhesive be applied it will skin over more rapidly making it more likely that the problem will be compounded by late placement.
e.g for Forbo Fix 414 use 2mm depth at 6mm centres, V notch trowel.
Note: If the ridges are not the right size, there may be insufficient fresh adhesive to grip the floorcovering. During the spreading movement, the trowel must be kept at the correct 60° angle. If too flat the adhesive ridges will be too low.