What your chair is standing on
Before you set a chair’s height, it’s worth knowing whether the chair stays where you put it. A base that rolls away when you shift, sticks when you try to move, or sinks slowly over an hour makes every other adjustment provisional — you’re calibrating against a moving reference.
This is the first step in the setup order and it’s the one nobody does, because a chair’s relationship with the floor is invisible until you go looking for it.
Three things that go wrong down there
Drift. The chair rolls when you don’t want it to. On a hard floor with hard casters this is constant, low-level, and it costs you something specific: you brace a foot against the floor or hook it round the base to stay put. That’s a small sustained effort in one leg, held all day, and it’s a fairly common hidden cause of one-sided tiredness at the hip.
Sticking. The opposite, and mostly a carpet problem. If moving the chair requires a shove, you stop moving it, and then you reach for things instead of rolling to them. A chair that’s hard to move quietly converts every retrieval into a lean.
Sinking. The gas cylinder loses pressure and the seat descends over minutes or hours. This one is genuinely insidious: you set the height correctly at nine, it’s wrong by eleven, and because it happened gradually you don’t register the change — you just find yourself with your shoulders up and no idea why. If you’ve ever had the feeling that you keep re-adjusting the same chair, check this before anything else.
CHAIR BASE — the check
Sit normally, hands off the desk.
· Shift your weight side to side. Does the chair move?
Moves freely on a hard floor → drift; you're bracing
Won't move without a shove → sticking; you're reaching
· Look at where your feet are. Is one of them braced
against the floor or the chair base? → drift, confirmed
· Mark the seat height against something fixed — a desk leg,
a bit of tape. Check it again after an hour of sitting.
Lower than the mark → cylinder is sinking
· Rock gently. Any wobble or clunk? → caster loose or
base crackedThe tape test for sinking is the one worth doing today. It takes no effort and it resolves a question people spend months confused by.
Fixing each one with what’s around
For drift on hard floors. The stock answer is a mat or a rug under the chair, and it works: a low-pile rug of any kind adds enough resistance that the chair stops wandering while still rolling when pushed. A doormat is too small; you want the whole travel range of the chair covered, or you’ll get a lip to bump over.
If a rug isn’t available, the casters themselves are usually the problem. Hard plastic casters are made for carpet; on wood, laminate or tile they roll far too easily. Casters are almost always a push-fit into the base and pull out with a firm tug or a bit of leverage — this is one of the very few places where a genuinely cheap replacement part solves the problem completely, and it’s a five-minute job with no tools. Soft-wheeled casters exist for exactly this. Alternatively, locking casters, or ones with a brake that engages under load.
For sticking on carpet. A hard, flat surface over the carpet. A chair mat is the purpose-built thing; a sheet of hardboard or thick plywood does the same job for less. Thick-pile carpet is the hard case, and if you can’t put something over it, the practical adaptation is to arrange the desk so you don’t need to move — everything you reach for within reach, which is a desk-layout problem rather than a floor one.
For sinking. The gas cylinder has failed and it does not come back. Cylinders are a standard part and swap out; whether that’s worth doing depends on the chair. The improvised version — a hose clamp tightened onto the exposed cylinder shaft at the height you want — genuinely works and fixes the chair at one height permanently, which is a real loss because you can no longer adjust it. Do that only once you’re confident the height is right.
For wobble. Check every caster is fully seated, then look at the base itself. Cracked five-star bases, especially plastic ones, are a safety matter rather than a comfort one; a base with a visible crack should be replaced or the chair retired.
The floor under your feet, too
Two smaller things that belong to the same subject.
A footrest needs the same treatment. If your chair is high enough that you’ve put a box under your feet, that box has to be stable. One that slides when you push against it is a thing you’ll unconsciously stop pushing against, which defeats it. Something with grip underneath, or wedged against the desk’s back panel, or heavy enough not to move.
Shoes count. This sounds trivial and it isn’t. A couple of centimetres of sole changes your effective leg length, which changes the footrest height you need and, if the chair is set from the floor, the chair height too. If you work in boots some of the year and barefoot the rest, expect to reset the footrest twice a year, and don’t be surprised when a setup that was fine in February feels wrong in July.
Where standing desks come into it
If you use a sit-stand desk, the floor question doesn’t go away — it changes. Standing on a hard floor for long stretches is its own kind of unpleasant, and the mitigation is a mat, or shoes with some cushioning, or simply not standing for as long. What a standing desk actually fixes covers the rest of it.
Also worth knowing: if the chair drifts, transitions between sitting and standing get more annoying, because you push the chair back to stand and it goes further than you meant. A chair that stays put is a chair that’s still where you left it when you sit down again.
What this doesn’t do
A stable chair on a suitable floor removes reasons to brace and reasons to reach. It doesn’t make sitting for hours a good idea — nothing about the floor changes the fact that no single position is comfortable for four hours, and getting up is the other half of the problem, which is a separate subject.
None of this treats anything. If you have persistent pain, or pain travelling down a leg, or numbness, tingling or weakness, that’s a reason to see a qualified clinician rather than to change your casters.
Do the tape test. Then set the height, knowing it’ll stay where you put it.