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How to assemble an office chair, step by step

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In short

Most office chairs go together in the same order: castors into the base, gas lift into the base, mechanism onto the seat, seat onto the gas lift, then the back and arms. Leave the back and arm bolts slightly loose until everything lines up, then tighten them fully. Assembly usually takes 15 to 40 minutes with the supplied Allen key.

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Flat-packed office chairs arrive in a box with a base, castors, a gas lift, a seat, a back, arms and a bag of bolts. The instructions are often just pictures. This guide sets out the order that works for most task, mesh and gaming chairs, explains the parts, and lists the checks to make before you sit down. Always follow your chair's own manual where it differs, as some designs pre-fit parts or use a different back bracket.

Before you start

Clear a floor space about two metres square and lay the box flat to use as a work mat, which protects the floor and the chair's finish. Unpack everything and check the parts against the list in the manual. Count the bolts: most chairs include one or two spares.

You usually only need the Allen key supplied. A cordless screwdriver with a hex bit saves time, but set the clutch low so you do not strip threads. Gloves help with mesh frames that have sharp moulding edges.

  • Five-star base and five castors
  • Gas lift cylinder, often with a plastic cover
  • Seat with or without the mechanism fitted
  • Back, sometimes with a separate back bracket
  • Arms, headrest and lumbar parts if supplied
  • Bolts, washers and Allen key

Assembly steps

This is the usual order. Your chair's manual may differ slightly, so check it at each step.

  1. 1

    Push each castor stem firmly into the holes in the base until it clicks or sits flush. Pressing the base down onto a hard floor helps.

  2. 2

    Stand the base on its castors and drop the gas lift into the centre hole, wide end down. Fit the cylinder cover over it if supplied.

  3. 3

    Turn the seat upside down on the box. If the mechanism is separate, bolt it to the seat with the lever on the side the manual shows, usually the right.

  4. 4

    Fit the arms to the seat, starting all bolts by hand and leaving them a little loose.

  5. 5

    Fit the back or back bracket to the mechanism or seat, again starting all bolts by hand.

  6. 6

    Line everything up, then tighten all bolts fully in a cross pattern.

  7. 7

    Turn the seat over and lower the mechanism's socket onto the top of the gas lift. Sit down firmly to seat the taper.

  8. 8

    Fit the headrest and any lumbar parts last.

The gas lift: what to know

The gas lift fits by a friction taper, not a thread or bolt. Your weight presses it home the first time you sit. Do not hammer it, and do not try to remove the cylinder by pulling once it has seated. If it ever needs replacing, our gas cylinder guide explains how.

Keep the lift's protective cap on until you fit it, and avoid getting grease or dirt in the taper, as that can stop it seating well.

Release pinTapered topOuter tubeNitrogen chamberSealPistonRod to the baseLengthin mmClass 3: standardClass 4: heavy dutythicker, stronger tube
Inside a gas lift. Class 4 cylinders are the heavy-duty grade; the length is measured in mm.

Checks before first use

Once built, run through these checks before you rely on the chair.

  • Every bolt is tight, with none left out or cross-threaded
  • The seat goes up and down smoothly when you use the lever
  • The tilt lock holds the back upright and releases cleanly
  • Arms are level and do not rock
  • All five castors spin and swivel
  • The chair does not lean when you sit centrally

Note:Check all bolts again after a week of use, as they can settle. A chair that leans, creaks or wobbles after assembly usually has a loose or cross-threaded bolt.

Set the chair up for you

With the chair built, set it to your body using the HSE display screen equipment points: feet flat, thighs roughly level, lower back supported, forearms level with the keyboard. Our office chair adjustment guide goes through each control in turn, and our lumbar support guide covers the back.

If the chair still does not fit after adjustment, check whether it suits your size. Our ergonomic office chairs guide and our tall people guide list chairs with wider ranges.

forearm roughly levelthigh roughly levelfeet flat123456
  1. 1Seat height (gas lift)
  2. 2Seat depth slide
  3. 3Lumbar height and depth
  4. 4Back angle and tilt tension
  5. 5Armrest height
  6. 6Headrest
The adjustment points of a task chair, with a seated outline: feet flat, thighs and forearms roughly horizontal.

Compare ergonomic office chairs →

Common assembly problems

Bolt will not start. Back it out, line up the holes by moving the part slightly, and start it by hand. Never force a bolt with a driver. Back is crooked. Loosen all back bolts, sit the back straight and tighten in a cross pattern. Lever on the wrong side. The mechanism may be fitted backwards; check the arrow marked on it, which usually points to the front of the seat. Squeak after assembly. Usually a bolt not fully tight; see our squeaking guide.

Frequently asked questions

How long does it take to assemble an office chair? Most take 15 to 40 minutes. Gaming chairs with recline mechanisms and side covers can take a little longer.

Do I need two people? Usually not, but a second pair of hands helps when fitting a heavy back to the seat.

Can I use a drill to assemble a chair? A screwdriver on a low clutch setting is fine for starting bolts. Do the final tightening by hand to avoid stripping threads.

Why does my new chair lean back? The tilt lock may be off or tension too low. Check the tilt lever and turn up the tension knob.

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