FACTORS THAT AFFECT SET UP
HAVE YOU EVER HAD A CUSTOMER COMMENT:
- The adhesive is not drying.
- The adhesive is not holding the carpet down.
- The adhesive is not sticking. It's still wet.
- The adhesive is not as good as the last batch purchased.
- The adhesive is not transferring to the floor covering backing.
- The adhesive is drying too quickly.
While adhesive performance will vary from company to company as well as within a company's own product line (e.g. Economy grade vs. premium grade products), manufacturing variables do not explain the performance differences noted from job to job and day to day when the same adhesive is used.
What would cause an adhesive that worked well yesterday to not work right today? To answer this question we initiated a study to determine the effect that certain variables encountered in the field have on adhesive set up time. The following are six factors that influence the adhesive set up time. They are listed in order of significant effect and are followed with suggested ways to control the variable when possible:
- SUBFLOOR POROSITY
(The ability of the floor to absorb moisture from the adhesive.)
Porous subfloors generally require less set up time than non-porous. Expect at least double the set up time when installing over non-porous floors like tile linoleum, sealed concrete, terrazzo and marble as compared to porous floors such as plywood and suspended or unsealed concrete.
RECOMMENDATION: Allow longer adhesive open time, circulate air with fans, decrease room humidity when installing over non-porous substrates.
NOTE: The use of sealers, primers, curing compounds, etc. could render a porous subfloor non-porous.
- HUMIDITY
(The amount of moisture in the air at a given temperature.)
The relative humidity influences the rate the moisture can evaporate from the adhesive. The higher the humidity, the longer the set up time. The Carpet & Rug Institute (CRI) recommends that the humidity not exceed 65% when installing carpet. Expect double the adhesive set up time when installing floor covering over a non-porous substrate at 75% relative humidity as compared to 25% relative humidity.
RECOMMENDATION: Allow longer adhesive open time, dehumidify air, increase room temperature, circulate air.
3. FLOOR COVERING BACKING
The more non-porous the floor covering, the longer the adhesive set up time. Expect longer adhesive set up time when installing synthetic (e.g. hot melt, ActionBac and vinyl) as compared to porous backing (e.g. jute and mineral fibrous felt).
RECOMMENDATION: Allow longer adhesive open time with non-porous floor covering backing, increase room temperature, reduce humidity. Ideally use a floor covering with a porous backing over an existing non-porous substrate.
- TROWEL SIZE
The deeper and wider the trowel notches, the greater the amount of adhesive used; therefore, the longer the adhesive set up time. Since an installer must use the recommended trowel for successful installation, this variable cannot be changed. Never use less adhesive to speed adhesive set up time. This will only result in loss of adhesion (installation failure) within 3 to 9 months.
- TEMPERATURE OF THE ADHESIVE
The colder the adhesive, the longer the set up time. We compared the adhesive set up time for an adhesive at 40 F vs. 70 F. We found that the adhesive set up time at 40 F took one hour longer than 70 F. Additionally, at 40 F the adhesive was thicker and more unstable over a concrete substrate.
RECOMMENDATION: Condition the installation site, all flooring materials and adhesive at 70 F.
- OPEN TIME
(The amount of time an installer has before the adhesive no longer transfers to the floor covering backing.)
When installing a non-porous backed floor covering or when installing over non-porous subfloor, allow the adhesive longer open time.
RECOMMENDATION: If the adhesive appears to have an unusually long open time, expect a long adhesive set up time. The same variables that affect adhesive set up time will affect the adhesive open time.
Even though there are some variable that cannot be controlled by the installer (e.g. type of flooring selected by the customer, type of subfloor, trowel size recommended for the installation) there are variables that can be adjusted to control adhesive set up time. Understanding these variables may help to explain why the same adhesive that worked well yesterday did not set up the same way today.