Furniture is one of the few things a household owns that was made to be repaired, and most of it can be brought back with glue and cramps and nothing else. It is also the thing most often ruined by the first attempt, in a specific and avoidable way.
Why the screw makes it permanent
A chair racks and creaks because a joint has opened up. The instinct is to drive a screw through it, or a nail, or to squirt glue into the gap without dismantling anything.
Every one of those makes the proper repair impossible later.
- A screw through a loose joint holds it in the wrong position, splits the timber it goes into, and leaves a hole that no future glue joint can span. Chairs held together with screws come loose again in a season, because the screw is carrying a load the joint was designed to carry across a large glued area.
- Glue squirted into a gap lands on the old glue and the dust, and cannot reach wood fibre. Wood glue bonds to wood, not to cured glue. It will hold for a few weeks.
- A nail does everything a screw does and splits more.
Take it apart instead. It is less work than it sounds, and it is the difference between a repair that lasts twenty years and one that lasts a fortnight.
Taking it apart
Work out which joints are loose and which are sound, and dismantle only what you must. Mark every joint before you separate it: a piece of masking tape on each part with matching numbers, or a pencil mark across the joint line. Furniture parts look identical and are not.
- Pull gently and evenly. Rock the joint apart rather than levering, and pull along the axis of the joint.
- Protect the wood. A block of scrap between any hammer or lever and the furniture.
- Old animal glue lets go with heat and moisture. A cloth wrung out in hot water, held on the joint for a few minutes, will often free a joint that seemed solid. This is why antique furniture can be dismantled and reglued repeatedly, and it is worth trying before force.
- Modern PVA does not release, and a joint glued with it may have to be sawn or accepted as it is.
- If a joint will not come and is not loose, leave it. You do not need to dismantle the whole chair to fix one leg.
Cleaning the joint
The step that decides the repair.
Every trace of old glue must come off both faces, down to clean wood.
- Scrape with a chisel or a knife, held nearly flat, taking off the glue without cutting into the timber.
- Hot water and a cloth for hide glue, which softens readily.
- Abrasive paper wrapped round a dowel for the inside of a round mortise.
- Do not sand a tenon so hard that it loses its fit. You are removing glue, not wood.
Check the fit dry. The joint should go together snugly by hand, with no rocking. Too tight and the glue is scraped off as it assembles; too loose and there is nothing for it to grip.
Regluing and cramping
- Dry fit the whole assembly first, with cramps, and check it stands square and does not rock. Adjust before there is glue anywhere.
- Have everything to hand: glue, cramps, blocks, a damp cloth, and a helper if it is a chair.
- Glue both faces thinly. The mortise and the tenon, or both sides of a dowel hole.
- Assemble quickly, in the right order, and get the cramps on within the open time of the glue.
- Cramp across the joint, not at an angle, with a scrap block under each cramp head.
- Check for square and check it does not rock on a flat surface before the glue sets. This is the last moment you can fix it.
- Wipe squeeze-out with a barely damp cloth, or let it go rubbery and pare it off.
- Leave it alone overnight. Handling time is not cure time. See adhesives.
A tourniquet works as well as a cramp on a chair: a loop of cord round the legs, twisted tight with a stick. That is how chairs were glued for centuries.
PVA for most repairs, waterproof grade if it will live in a damp room. Animal hide glue if you want the repair to be reversible in future, which on anything old or valuable is the right answer.
A joint that is now loose in the hole
Common on an old chair where the tenon or the dowel has shrunk and the mortise has worn.
Do not fill the gap with glue. A thick glue line is weak, and glue does not have gap-filling strength.
- Best: build the tenon up. Glue a thin shaving or veneer to the cheeks of the tenon, let it dry, then pare it back to a snug fit. This restores wood to wood contact.
- Replace the dowel with a new one of the correct size, and re-drill the hole cleanly if it has become oval.
- Wrap the tenon in a thin cloth or a shaving soaked in glue, as a last resort, which works and is less durable.
- Epoxy is the honest fix for a badly worn joint, because unlike PVA it has real gap-filling strength. It is not reversible, so keep it for things that are not precious.
Swelling the wood with water is a temporary trick, not a repair. It holds for a season and comes loose again as it dries.
Splits and cracks
A split along the grain can usually be glued and cramped, because the two faces still match perfectly.
- Open the split gently, just enough to work glue in with a thin blade or a piece of paper.
- Work glue into the whole depth.
- Cramp across the split, with blocks, and check the surfaces line up flush.
- Wipe and leave overnight.
A split that will not close has moved, and forcing it will break something else. Fill with a sliver of matching timber glued in, then pare flush.
A crack across the grain is a break rather than a split and needs reinforcement, not just glue. A patch or a spline set into a saw kerf across the break.
Broken parts
- A broken chair leg or rail usually breaks with a long diagonal grain line, which is good news: those faces have a large area and glue extremely well. Clean, glue, cramp, and it will often be stronger than before.
- A short-grain break, snapping straight across, has almost no gluing area and will fail again. Reinforce with a dowel drilled through the break, or a spline, or replace the part.
- Replacing a part is often easier than a heroic repair. A chair rail is a straight piece of timber; copy the old one.
- Corner blocks are the unglamorous secret of chair strength. Small triangles of timber glued and screwed into the inside corner of a seat frame stop the frame racking, and adding them where they are missing is one of the highest-value jobs on this page.
Wood moves and your repair must let it
The idea that explains a lot of failed furniture repairs.
Timber moves across the grain with humidity, and essentially not at all along it. A board a foot wide can change width measurably between a damp winter and a dry heated room. If a repair fixes the wood so it cannot move, the wood splits instead.
- Never glue a solid wood tabletop rigidly across its width to a frame. Tabletops are held with buttons, slotted brackets or screws in elongated holes, precisely so they can move.
- Never glue a batten across the grain of a wide board to stop it cupping. It will split the board.
- A patch let into a wide board should be glued along the grain and left free to move across it, or kept small.
- Plywood does not move and can be fixed rigidly, which is why it is used where solid timber would fail.
In an unheated house this matters more than usual, because the swing in humidity is much wider than in a centrally heated one. See damp and mould for the related problem of the air itself.