Repairing Wood: Strong Glue Joints in Wood

How to glue wood joints that are stronger than the wood itself.

Repair broken furniture and cracked woodwork, make stronger woodworking projects, and learn how to make cleaner, tougher glue joints with these gluing tips and techniques.

By the DIY experts of The Family Handyman Magazine
You might also like: How to Glue Wood

Apply tape to control glue squeeze-out

Use tape to clamp cracked wood

It's often tough to repair cracked cabinets and furniture with regular clamps. But transparent tape makes a great substitute. If the wood is just cracked, flatten the end of a drinking straw and blow the glue into the crack. Then tape it.

If a piece has broken off, follow Photos 1 and 2. One drawback: Super-sticky tape can pull off finishes and paint when you remove it. Use light-duty tape or adhere regular tape lightly. And remove it as soon as the glue dries.

Clean and clamp when regluing a chair

Regluing a chair is challenging because you usually have to at least partially disassemble the chair and glue the same joints all over again. One critical step is to clean off every bit of the old glue. There will be quite a bit of it, since you'll probably have several loose joints and may have to knock others apart to disassemble the loose ones. You have to clean both the dowel end (Photo 1) and the socket (Photo 2). The trick is to do it without digging into the wood. The more wood you shave away, the larger the gaps that the new glue will have to fill. Use sandpaper only as a last resort, because it tends to sand away wood as well as glue.

You'll find the steel brushes for cleaning the sockets (Photo 2) in the plumbing section of a home center or hardware store. They're designed to clean the insides of copper pipe and fittings and are available in several sizes.

Clamping may call for creativity (Photo 3). The trick is to first dry-fit all the parts you intend to glue at one time. If possible, glue the chair in two stages: the seat and legs first, and then when they're dry, the backrest section. Test-fit the clamps to make sure where every clamp will go. Then you can work swiftly when applying the glue. Even so, use liquid hide glue rather than yellow glue; hide glue gives a much longer open time before “grabbing,” so you can get all the parts and clamps in place.

Add glue blocks

Glue and screw whenever possible

Screws are ideal for joints that call for extra strength, or where accurate positioning of a glued piece would be difficult.

Insert glue biscuits to double joint strength

They may not be good to eat, but glue biscuits are the do-it-yourself cabinetmaker's best friend. A biscuit joiner (Photo 1) is very user friendly and simple to operate. It cuts precise oval slots in the ends and the surfaces of wood parts that enable you to position the parts for clamping and gluing quickly and accurately. The glued-in-place biscuits provide broad gluing surfaces that make for a strong joint. A special glue bottle (Photo 2), available from woodworking suppliers, speeds up the application of glue and distributes it evenly in the slots. Don't delay during glue-up! Biscuits swell after gluing (which adds to their strength), so you don't have much time for assembly. Preassemble with dry biscuits to check fits—you won't get a second chance.

Spread glue evenly on large areas

Reminders for strong glue joints

  • Make sure your gluing surfaces are clean and smooth but not too glossy. Rough surfaces don't allow enough glue contact. Glossy surfaces prevent the glue from penetrating the fibers and getting a good grip. You can sand lightly to smooth roughness or remove gloss, but don't try to actually shape a joint by sanding; it's impossible to get a good mating fit that way. If you're sanding, use a block and be careful not to round over sharp edges.
  • Clamp all glued joints. Pressure is necessary to form a tight, gap-free bond, and to help force glue into the wood fibers. Clamping also prevents movement while the glue is hardening. In situations where you can't use clamps, use screws, elastic cords or weights.
  • Do a dry run with clamps before you apply any glue. This not only allows you to check for a good fit but also ensures that you will have your clamps adjusted to proper length, and all other necessary tools at the ready. It's important to complete a glue-up fairly quickly; even though it takes about an hour for most wood glues to set and 24 hours to cure, the initial “grab” takes place in two or three minutes, and clamping should be completed by then.
  • Get a good fit between the two glued surfaces. Wood glues (except for epoxy) won't bridge gaps, so any joint with gaps will be weak. The parts should fit together snugly. If you can't reshape the part with a router or table saw, try gluing thin wood curls in place to fill the gaps. (You can cut curls from a scrap board using a wood plane.)

Choose the best type of glue

Required Tools for this Project

Have the necessary tools for this DIY project lined up before you start—you’ll save time and frustration.

  • Clamps
  • Cordless drill
  • Biscuit joiner
  • Countersink drill bit
  • Rags
  • Rubber mallet
  • Utility knife

You'll also need a glue spreader, a biscuit-slot glue tip, a round wire brush, and elastic cords.

Required Materials for this Project

Avoid last-minute shopping trips by having all your materials ready ahead of time. Here's a list.

  • Sandpaper
  • Glue
  • Clear sealing tape
  • Masking tape

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