Wood Glue Can Last for Years
Use Waterproof Glue for Outdoor Projects
If your carpentry project might get wet, use glue that stands up to water. Glues labeled 'water resistant' are fine for things that'll only get wet occasionally. For most outdoor projects, however, choose 'waterproof' glue, which comes in both PVA and polyurethane formulas. Both types are plenty strong and stand up to the weather, but polyurethane glue has the added benefit of being able to bond materials like stone, metal and glass. It's messy stuff, though, so wear gloves while using it.
Mask Glue Joints Before Prefinishing
Finishing the parts of your project before you assemble them can be a great time-saver and allow you to get a better-quality finish. But for a strong glue joint, you have to keep the joints free of finish (glue doesn't stick to varnish or stains very well). The solution is to apply masking tape to the surfaces that will be glued. Then remove it to expose raw wood when you glue up the project. Any good-quality masking tape will work. If you'll be using a water-based finish, you'll get the best results with a “no-bleed” tape such as green Frog Tape and ScotchBlue painter's tape.