Letters

Readers dispel concerns about water-based adhesives

I am writing regarding "A growing concern," December 2011 issue, page 12, by Mark S. Graham, NRCA's associate executive director of technical services.

Water-based adhesives, similar to all roofing products, are subject to certain limitations. In the case of water-based adhesives, the limitation is minimum application temperatures. The article fails to mention the significant benefits of these products. Beyond the obvious advantages of their low volatile organic compound content (less odor, reduced risk of ignition on the roof), they are easier, much faster to install and much less sensitive to application errors than their solvent-based counterparts.

Our water-based membrane adhesive was introduced in 1979. Since that time, it has been used successfully on hundreds of millions of square feet of PVC roof system installations throughout the U.S. and world. Many of our oldest installations, which have been in place for decades, still are in service and were installed using our water-based adhesive.

It is unfortunate Graham chose to paint the entire segment with such a broad brush. Manufacturers offer different adhesives and membrane types with different physical properties. For decades, we have demonstrated water-based adhesives are an effective, proven option for adhering PVC roof membranes.

Further study of this application may be warranted. We would welcome the opportunity to work with NRCA to further clarify this subject.

Stanley P. Graveline
Sika Sarnafil Inc.
Canton, Mass.

This letter is written in response to "A growing concern," December 2011 issue, page 12, by Mark S. Graham, NRCA's associate executive director of technical services.

Although SPRI agrees waterborne adhesives may have temperature limitations that differ from solvent-based adhesives, it should be noted all adhesives used for bonding single-ply membranes to substrates, including solvent-based and 100 percent solids-reactive adhesives, have their own set of limitations and precautions.

Waterborne adhesives have been used successfully in the single-ply industry for more than 20 years. Certainly, temperature during application and storage are major considerations. However, even solvent-based adhesives should only be used when temperatures are 40 F and rising and stored between 60 F and 95 F. Solvent-based adhesives also are affected by temperatures below freezing, which can cause increased viscosity resulting in a lower coverage rate; excessive adhesive coating; puddling resulting in solvent entrapment, blisters and lack of adhesion; and substantially longer cure time.

As with all adhesives, it is important applicators read and follow manufacturer instructions. If an applicator is unsure of the proper use of an adhesive or the project appears problematic, the applicator should contact the respective manufacturer and NRCA's Technical Services Section for assistance.

Waterborne adhesive use has accelerated, driven by standards and regulations limiting the permissible volatile organic compound (VOC) content. Some solvent-based adhesives also have been redesigned to reduce their VOC content and now are compliant with regulations.

There has been excellent response by the roofing industry to meet or exceed VOC regulations and improve the environment, and SPRI supports these actions. SPRI also supports full disclosure of all adhesive concerns and problems so corrective action may be taken and also endeavors to provide guidance and advice to prevent problems from occurring in the first place.

To this end, SPRI and NRCA have entered into a collaborative effort to define the advantages and limitations of waterborne adhesives and distribute this information in a white paper prepared for the single-ply industry—contractors as well as specifiers. SPRI welcomes the efforts and will work closely with NRCA to accomplish this goal. This joint effort will have a much greater effect and quickly will facilitate information distribution as compared with a singular effort.

Mike Ennis
SPRI
Waltham, Mass.

Graham responds: Thanks to Sika Sarnafil and SPRI for providing their comments and some additional useful information. NRCA and I look forward to working with both, as well as other manufacturers, in addressing the concerns raised.

The purpose of my December 2011 column was to notify Professional Roofing readers of some concerns being raised associated with water-based bonding adhesives and not to single out any particular manufacturer. NRCA's Technical Services Section has received feedback about virtually all manufacturers' water-based bonding adhesive products, and none is immune to challenges in field application situations.

One fundamental question that needs to be answered regarding water-based bonding adhesives is what roofing contractors should do when storage temperatures, application temperatures and humidities fall outside of those required in manufacturers' printed installation instructions. This is the case for a large portion of the U.S. this time of year. Should roofing contractors suspend roofing operations until conditions are more favorable, possibly for months? Should roofing contractors change the roof system to something that is not as sensitive to storage and application environments?

I already can foresee the response from general contractors and building owners: "Put the [insert expletive] roof on the building, or I will find someone else who will."