Q. For one of our projects, we need to make a solid wood attachment to a glulam beam that seems to have a special finish on it. Should we use a particular type of glue to make the connection?
A. Mark Stypczynski, manager of technical development at AkzoNobel/Liquid Nails in Strongsville, Ohio, responds: Two types of sealers meet the American Institute of Timber Construction standards for protecting glulams during transit, storage, and construction (AITC 111-05). One is a translucent penetrating sealer, and the other is a nonpenetrating coating. If your glulam is protected by a penetrating sealer, use a subflooring adhesive that meets either APA specification AFG-01 or ASTM D-3498 (adhesive manufacturers will list one or both of these standards on their product label).
Some of our products that meet these requirements are Liquid Nails Subfloor & Deck Construction Adhesive (product codes LN-602 and, for the low-VOC version, LN-902) and Polyurethane Construction Adhesive (LN-950). Other manufacturers — such as Henkel/OSI, Franklin, and TACC — also have subfloor adhesives that meet the standards.
If your glulam has a nonpenetrating coating (it will be obvious on inspection), the coating could potentially interfere with adhesion. If your glulam manufacturer doesn’t list a specific adhesive in its literature, contact an adhesive manufacturer for a recommendation. Glulam manufacturers typically know what type of coating is used on their product — but not necessarily what adhesive will work with that coating.
Keep in mind that regional differences in air-quality regulations (including limits on VOCs) may preclude the use of certain adhesives in some areas.