Polyurethane vs. Titebond III

Like most carpenters, I started using polyurethane glue for exterior trim work because it’s 100% waterproof. But I’ve never liked working with the stuff. Polyurethane glue foams and expands as it cures, so mating parts need to be clamped for a few hours until the glue sets. Otherwise, the foaming action can push the joint apart.

Applying the right amount of polyurethane glue takes experience. Some should squeeze out after the glue cures, but excessive dried glue is a pain to scrape off. Skin contact also is a problem. I have to wear latex gloves whenever I use the glue because if it gets on skin, it can cause a sticky stain, or worse, serious irritation. Still, the payoff is worth the hassle: durable joints that I’m confident will hold up.

When Titebond III hit the market, it changed the whole playing field. Hailed as the first waterproof polyvinyl acetate (PVA) glue, Titebond III is marketed specifically for use on exterior wood-to-wood applications, and it’s great for exterior trim work. It also is more effective in colder temperatures. Because of its higher strength and lower cost, I now substitute Titebond III for polyurethane in many situations.

Still, Titebond III can be used only on wood. Given that polyurethane glue is not only dependably waterproof but also bonds to almost any surface—glass, brick, tile, concrete, steel, and wood—I’m sure I’ll keep a bottle of each handy for a long time to come.

—Gary M. Katz, contributing editor

Polyurethane

• Open time: approximately 15 minutes for Gorilla Glue; 25 to 35 minutes for Excel One
• Clamping time: Two to five hours
• Cleans up with denatured alcohol
• Cost: Gorilla Glue, $14 for an 8-oz. bottle; Excel One, $10 for an 8.5-oz. bottle

Titebond III

• Open time: approximately 10 minutes
• Clamping time: 30 minutes
• Cleans up with soap and water
• Cost: $5 for an 8-oz. bottle

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