As a woodworker, I'm often asked to repair loose chairs. The traditional approach is to take the chair apart, remove the old glue, and reglue the joints. And when several joints have failed, that may be the best solution.
But there's a potential problem when only one or two joints are loose. Disassembling the chair means separating joints that may still be perfectly sound, increasing the chance of damaging the chair in the process.
In that situation, I've had good results focusing on the loose joint and injecting a specialized glue directly into it.
Use an Injectable Glue for Loose Chair Joints
The system I've used is the Chair Doctor Pro kit from Veritas. The kit includes low-viscosity glue, a syringe, and needles in three different diameters. A simpler version is also available with a small bottle of glue and a single needle.
The advantage of the syringe and needle is that you can get glue into a loose mortise-and-tenon joint without necessarily pulling the joint apart.
Inject Glue Directly into the Loose Joint
First, inspect the loose joint and see whether there's enough of a gap between the mortise and tenon to insert one of the applicator needles.
If there is, that's the simplest approach. Insert the needle into the gap and inject the glue directly into the joint.
The small applicator makes it possible to get the adhesive where it's needed while keeping the repair discreet.
Drill a Hidden Access Hole if Necessary
Sometimes a joint is loose but the opening around the tenon isn't large enough to accept the needle. In this situation, the manufacturer's recommended technique is to drill a small pilot hole that provides access to the mortise.
Locate the hole underneath or behind the mortise whenever possible. This keeps the access point out of sight after the repair. Drill only as far as necessary to reach the joint. Then insert the appropriate needle through the hole and inject the glue into the mortise.
Woodsmith Tip: Before drilling, study the joint carefully so you understand the location and direction of the mortise. The goal is to create a small access point into the joint—not drill through the chair part.
Why Chair Repair Glue Is Different
The glue supplied with the Chair Doctor system has a lower viscosity than typical woodworking glue. That allows it to flow into the small spaces between a loose tenon and its mortise.
According to the product's intended method, the thin adhesive also penetrates the end grain of the tenon and causes the wood fibers to swell. This helps an undersized tenon fit more tightly inside the mortise.
That's an important distinction from simply trying to force ordinary woodworking glue into a partially opened joint. The low-viscosity adhesive and needle applicator are designed specifically for getting adhesive into an assembled joint.
Clamp the Chair Joint
Once the glue has been injected, bring the joint firmly back together. I recommend clamping the joint until the adhesive sets.
Use enough pressure to close the joint securely without distorting the chair or damaging its parts. Wipe away any adhesive that appears around the joint and allow the glue to cure according to the manufacturer's directions before putting the chair back into service.
RELATE PLAN: 5 Shop-Made Clamps
When Should You Take the Chair Apart Instead?
This injection method makes the most sense when you're dealing with an isolated loose joint while the surrounding joints remain sound.
If several joints are loose, parts are damaged, or the existing joinery has substantially failed, a more complete repair may be appropriate. That can mean carefully disassembling the affected portion of the chair, cleaning the mating surfaces, and regluing the joints.
But there's little benefit in disturbing sound joinery simply to reach one loose mortise and tenon.
For the right repair, injecting glue directly into the problem joint provides a simple alternative that can save a considerable amount of disassembly—and help preserve the rest of the chair.
