How do I keep assembled furniture from loosening over time?

Assembled furniture stays tight when it is built completely, tightened without stripping, checked as the seasons change and kept dry. The rest is how you treat it: lift instead of dragging, load heavy things low and fasten tall pieces to the wall so they do not rock every time a drawer opens.

Why assembled furniture loosens

Three things work on it every day.

Use. Every drawer pulled and every lean against a bookcase flexes the joints a little. Cam locks and screws that were only just snug slowly back off.

Humidity. "Wood in service is always undergoing slight changes in moisture content."^[1] The Wood Handbook explains that changes from daily humidity swings are usually small, while seasonal changes are gradual but of more concern.^[1] Indoor wood's moisture depends mainly on indoor relative humidity, which air conditioning, ventilation and moisture sources in the house all affect,^[1] and finishes slow wood's dimensional changes but do not prevent them.^[1] A house that is humid in summer and dry with the heat on in winter puts every piece through that cycle once a year.

The material. Particleboard is the predominant material in ready-to-assemble furniture,^[3] and it holds a screw well only if the threads in it stay intact. The Forest Products Laboratory warns that care must be taken when tightening screws in particleboard to avoid stripping the threads,^[2] and notes that a modest tightening of screws in many cases is an effective compromise between holding strength and stripped threads.^[2]

Build it to last

Most loosening starts on assembly day.

• Use every part. Dowels, cam locks, back-panel nails and corner brackets all share the load. A piece missing a few of them will loosen sooner.
• Fit the back panel properly. On bookcases, wardrobes and dressers, the thin back is what keeps the frame square. Seat it in its grooves and fasten it at every point the instructions show.
• Turn every cam until it is snug. A cam lock that is only part way round leaves its joint free to move.
• Finish screws by hand. A cordless driver is quick for starting screws, but set the clutch low or finish them with a hand screwdriver.

A seasonal check

When the air conditioning or the heat starts running for the season, go round your assembled furniture with a screwdriver and the hex key. Snug any cam lock or screw that has backed off, gently. Check bed frames and desk chairs, which take the most movement, and any piece a child climbs or pulls on. If a screw spins without tightening, repair the hole with wood glue and a wooden dowel or toothpicks before the joint around it works loose.

Keep humidity steady

Big swings are what move wood the most. Virginia Cooperative Extension describes 40 to 55 percent relative humidity as comfortable and healthy for a building,^[4] and the EPA advises homeowners to keep indoor humidity below 60 percent, ideally between 30 and 50 percent.^[5] You can check it with a moisture or humidity meter, which many hardware stores sell.^[5] Running a dehumidifier in a damp basement in summer and keeping furniture away from heating vents and radiators both help.

Keep particleboard dry

According to the Wood Handbook, most panels made from particles swell in thickness when they get wet, and that swelling does not go back down.^[3] A swollen edge never closes up tight again. Wipe spills at once, keep mop water off the bottom edges, use a tray under plants and keep particleboard furniture off a basement floor that gets damp.

Move it gently

Empty the drawers and lift a piece to move it; dragging a loaded dresser across carpet twists the frame. For a long move, take large pieces apart, bag and label the hardware, and when you rebuild, drive screws back into their old holes by hand so they find their original threads.

Load it and anchor it

Keep the weight low. The warning labels the dresser safety standard calls for include placing the heaviest items in the bottom drawer and not opening more than one drawer at a time.^[6] A low centre of weight also means less rocking on the joints.

Fasten tall pieces to the wall. CPSC's advice is to "Anchor furniture to the wall or the floor."^[7] A dresser or bookcase held to a stud does not sway, which also spares its joints. See how to anchor furniture to the wall.

Stop and call a pro if

• Panels have swollen or crumbled around the hardware, so cams and screws no longer pull tight.
• The same joint keeps loosening after it has been repaired, or a panel has cracked.
• A loft bed, bunk bed or loaded bookcase has loose joints; anything people sleep in or under should be repaired properly before it is used again.
• Furniture in a damp basement shows swelling, mildew or a musty smell, which points to a moisture problem in the house, not just the furniture.

If a piece already rocks, start with why flat-pack furniture wobbles. You can also browse assembly and mounting services, find handyman businesses around Blacksburg, or read the other handyman answers.

To have loose furniture tightened, repaired or anchored, describe the job on Loclis and local businesses will quote it.