Should I glue flat-pack joints, and which ones?

Flat-pack joints are designed to be taken apart, which is exactly why they are the weakest part of the furniture. Gluing them trades that reversibility for real rigidity. It is a genuinely good idea on some pieces and a genuinely bad one on others, and the deciding question is not strength — it is whether the thing will ever move again.

What you'll need

• PVA wood glue, or polyurethane glue for chipboard
• Damp cloth for squeeze-out
• Tape measure, for checking diagonals before it cures
• Clamps or a strap (optional)
• Small brush or a cocktail stick for applying into dowel holes (optional)

Step by step

1. Decide on permanence first, not on strength.A glued carcass cannot be dismantled and moved. If you rent, move often, or the unit will not fit through a door assembled, do not glue it. That decision is irreversible and it is the whole trade-off.
2. Glue the dowels, not the cams.Dowels are what glue works on: end grain into a snug hole. A glued cam cannot rotate, so it cannot clamp anything, and glue in a cam hole is simply a jammed fitting.
3. Use the right adhesive for chipboard.Ordinary PVA works and is easiest. Polyurethane glue works better on chipboard because it foams slightly into the loose particles, but it expands, stains skin and must be cleaned up before it cures. Avoid instant superglue, which is brittle and gives no assembly time.
4. Put glue in the hole, not on the dowel.A dab inside the hole with a stick or a brush. Glue smeared on the dowel is scraped off as it goes in and squeezes out onto the visible face.
5. Work fast and check the diagonals immediately.You have perhaps ten minutes with PVA. Assemble, tighten the cams, measure both diagonals, adjust, then leave it. Getting this wrong is how people end up with a permanently leaning cabinet.
6. Wipe squeeze-out at once with a damp cloth.Dried PVA on a melamine face will not take a finish and shows as a shiny patch forever. On raw chipboard edges it seals the surface and stops later repairs sticking.
7. Consider gluing only the critical joints.A sensible middle path: glue the joints in the base and the top rail, which take the load and the racking, and leave shelves and internal fittings dry so they can still be adjusted.
8. Leave it undisturbed to cure.PVA needs a few hours before it takes any load and a day before full strength. Do not load a glued unit the same evening.
9. Anchor it to the wall anyway.Glue makes the carcass rigid. It does nothing about tipping over, which is a separate problem with a separate solution.

Tips

• For a second-hand unit being rebuilt, glue is often what makes it worth rebuilding — the holes are already slightly worn and dry joints will never be tight again.
• If you want strength without permanence, screws through the joints from a hidden face are almost as effective and can be undone.
• Never glue a unit you have not measured for the doorways it must pass through in its final assembled form.

Common mistakes

• Gluing a unit that will need to be moved — A glued carcass has to be broken to come apart, and chipboard does not survive that. It becomes a one-address piece of furniture.
• Putting glue into the cam housing — The cam has to turn to clamp. Glued, it is a jammed fitting and the joint has no clamping force at all.
• Gluing without checking the diagonals within the open time — The carcass sets in whatever shape it is in. There is no second chance once the glue has grabbed.
• Using superglue on chipboard — It cures brittle, soaks into the loose particles without bonding them, and gives no time to square the carcass.

If it doesn't work

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