How to install gas struts?

Updated October 2026. A gas strut is the fitting that lifts a wall-cabinet flap, holds it open and lets it close in a controlled way. Installing one takes about twenty minutes per flap, but only if the force in newtons, the strut length and the two fixing points are right – a strut that is too weak lets the flap fall, a strut that is too strong makes it impossible to close. This guide covers the choice of strut, the mounting geometry and the fitting itself, step by step.

What furniture gas struts are used for

Gas struts (also called gas springs, gas lifts or flap stays) are fitted wherever a front opens upwards: wall cabinets in the kitchen, lift-up doors on sideboards and TV units, chest and ottoman lids, campervan overhead lockers and loft hatches. Inside the cylinder, compressed nitrogen pushes the piston rod out with a defined force; a small amount of oil at the end of the stroke damps the last few centimetres so the flap opens smoothly rather than snapping up. The force printed on the cylinder – 30 N, 60 N, 80 N, 100 N and so on – is the nominal extension force. The range by force and colour is listed under gas struts: silver, black and white.

Step 1: choose the force

The required force depends on the weight and the height of the flap, not on its width alone, because the flap acts as a lever around the hinge line. A practical rule for the standard 250 mm furniture strut on a 300–400 mm high flap:

• 30–50 N – light flaps: glass or 16 mm board up to about 1.5–2 kg (small wall units, display cabinets).
• 60–100 N – medium flaps: 18 mm board, 2–4 kg (standard 600–800 mm kitchen wall units).
• 120–200 N – heavy or tall flaps: 19 mm board with handle, 4–7 kg, 500 mm high or more.
• Two struts – on flaps wider than about 600 mm fit one strut on each side and halve the force per strut; the flap opens evenly and the hinges are not twisted.

Weigh the flap with its handle on kitchen scales before buying. If the value falls between two classes, take the lower one for a flap that should be easy to close and the higher one for a flap that must stay open with a load on it. The full calculation with the lever effect is explained in how to match newton force to the flap material and what the newton rating on a gas strut means.

Step 2: measure the strut

Furniture struts are specified by the extended length between the centres of the two end fittings – 250 mm is the standard for wall units with a carcass height of 300–400 mm – and by the stroke, usually 80–100 mm. When replacing a strut, measure the old one fully extended, eye to eye, and read the force from the cylinder; when fitting from new, the 250 mm strut covers almost every kitchen wall unit, and longer struts are used for tall lift-up doors and chest lids.

Step 3: understand the mounting geometry

• Orientation: fit the strut with the cylinder at the top and the piston rod pointing down when the flap is closed. In this position the oil sits at the seal, the rod stays lubricated and the strut lasts years longer. A strut fitted the other way up works, but wears quickly and loses pressure.
• Carcass bracket: on the inside of the cabinet side, towards the back, roughly 50–80 mm below the top panel. This is the fixed end (cylinder).
• Flap bracket: on the inside of the flap, at about one third of the flap height measured from the hinge line, and far enough from the side (20–30 mm) for the strut to clear the carcass.
• Angle: with the flap closed the strut lies at a flat angle, with the flap open at 90–110° it points steeply upwards. The two brackets must not be in line with the hinge pivot, otherwise the strut has no lever and the flap falls.
• Hinges: use hinges without a closing spring, or with a very weak spring, so the strut is not fighting the hinge; 110° or 155° cup hinges are typical (cabinet hinges).

A detailed treatment of the fixing points and the angle is in mounting orientation and fixing points.

Step 4: fit the strut

1. Hang the flap on its hinges and adjust it so it sits flush and closes properly on its own weight.
2. Open the flap to the intended angle and have a helper hold it, or prop it with a batten.
3. Hold the strut in position, cylinder up, and mark the carcass bracket first. Screw the bracket on with the supplied 4 x 16 mm screws (pre-drill with a 2.5–3 mm bit in chipboard).
4. Clip the cylinder end onto the carcass bracket, swing the strut up to the flap and mark the flap bracket so the strut is not under tension when the flap is fully open. Screw the bracket on.
5. Clip the rod end onto the flap bracket. The ball-socket ends click on and are released with a small screwdriver under the spring clip.
6. Close the flap slowly: it should need a gentle push over the last third and stay closed. Open it: it should lift from about 15–20° on its own and stop without bouncing.

Step 5: adjust and troubleshoot

• Flap falls closed – force too low or the flap bracket too close to the hinge line. Move the flap bracket further from the hinge (more lever) or fit the next stronger strut.
• Flap hard to close – force too high or the bracket too far from the hinge. Move the flap bracket towards the hinge by 10–20 mm before changing the strut.
• Flap opens unevenly – on wide flaps fit a second strut on the opposite side.
• Strut hisses or loses force after months – usually fitted rod-up; refit cylinder-up or replace it (see how to replace gas struts).

Fine adjustment of the opening angle and the hold-open position is covered in how to adjust gas struts. If you are weighing up a strut against a friction stay, read gas struts vs mechanical flap stays.

Frequently asked questions

Which way up does a gas strut go?

Cylinder at the top, piston rod pointing down with the flap closed. The oil then lubricates the seal and the strut keeps its pressure for years.

How many newtons do I need for a kitchen wall unit?

For a standard 18 mm flap on a 600 mm unit, 60–80 N with a 250 mm strut is typical; weigh the flap and check the lever rule above before buying.

Can I fit one gas strut to a wide flap?

Up to about 600 mm one strut on the side away from the handle is fine; wider flaps need two struts so the door does not twist.

Do I need special hinges?

Use cup hinges without a closing spring (or with a weak spring) so the hinge does not pull the flap shut against the strut; 110° or 155° hinges suit most wall units.

Can gas struts be fitted to a lid that opens downwards?

Yes, with a reverse (traction) strut or a strut fitted in the mirror position so that it damps the downward movement; see gas struts vs gas traction springs.