Understanding the Causes of Adhesive Failures
The need for the installer to plan each job carefully, in order to work more efficiently, is obvious because planning contributes to the installer's profit. Unfortunately, many small installation firms do not know how to estimate and bid, and simply meet the price of others.
The planning of jobs is essential to cost control, as in its absence waste and delays creep into the work; in time this can cause failures as the installer speeds up his work to cut his losses. It is especially important to lay out the job so as to match textures, colors and patterns of floor and wall coverings and to control the location of seams and joints. Then there are such planning areas as preparation of substrates, scheduling of crews, provision for unusual job conditions, insistence upon safety and good workmanship. With respect to adhesives, it is vitally important to schedule the work so that the adhesive will be used properly within its open time, so that it will dry solidly.
In spite of its importance, careful planning is not nearly as common among subcontractors and applicators as it should be; inferior and/or incorrect materials are often used on jobs and cause problems of various kinds. This generalization may apply to adhesives, carpet/vinyl tile, sheet goods, laminate, ceramic tile and wood. There seem to be three main reasons that applicators may mistakenly purchase the wrong product:
• Excessive concern about buying at the lowest possible price
• Insufficient knowledge about what is needed to achieve good results
• Bad advice from a distributor, salesman or a piece of product literature
On most jobs, the cost of adhesive is a very small part of the total cost of the work in place, perhaps three percent or less. Therefore, "cheap" adhesive doesn't represent a large potential for savings. In addition, it is my experience that below a certain minimum cost level, it is just not chemically possible to manufacture consistent, reliable, satisfactory mastic. Excessive concern about price is often self defeating, and use of low-price products can result in call-backs that are far more expensive.
It is, of course, important to select the proper adhesive for the job to be done. To do this, consideration must be given to open time, working qualities, ability to bond to the adherents, "grab" drying rate, water resistance and similar properties. All of this information is carried on labels and data sheets of adhesive manufacturers but is frequently ignored by distributors and installers alike.
When a complaint occurs, it seems that the vast majority of installers do not read labels or data sheets before starting a job, because they assume that: all products work alike; nothing changes significantly in the trade; they know all about the product already from past experience.
To some degree these assumptions are partly true and understandable; however, good job practice should require every installer, distributor counter man and distributor salesman to keep up to date on changes that have been made to labels and material data sheets for possible additions and changes.
The elements of a good installation, and thus minimal chance for adhesive failure, are:
• A clean, solid substrate
• A substantially dry surface
• A reasonably flat surface
• A tolerable degree of porosity in the substrate (not too high or low)
Several years ago, a study was made of product complaints received; only three occur with any regularity: ceramic tile does not stick as expected, usually to walls; carpet is laying loose (not bonded to substrate); adhesive does not set up; bubbles show up on the surfaces of certain carpets or vinyl sheets goods.
These occurances are easily explainable, as follows:
Ceramic tiles that do not stick, and carpets that lay loose result when: • Too little adhesive is used; i.e. "spread" is too great.
• The mechanic exceeds the open time; i.e. works with the adhesive when it is too viscuous to wet the surfaces to be bonded.
• An unduly porous substrate, such as particle board, prematurely sucks vehicle out of the adhesive; i.e. the layer of adhesive is too dry when the covering is placed.
Adhesive that does not "set up" results when evaporation or adequate suction does not occur because it was placed upon a: damp or wet substrate that cannot absorb more water; non-porous surface, such as ceramic tile, that cannot absorb water at all.
Bubbles arise when there is too much air at the interface between floor covering and substrate, and are caused by:
• Too little adhesive, thereby permitting air to collect in pockets.
• Job not properly rolled, thereby not forcing air through the covering, or out the edges.
• Carelessness in working with the covering; i.e. throwing it loosely on the substrate instead of carefully unrolling it so as to prevent or eliminate the trapped air.