How to Install Gas Struts — Step-by-Step Guide

A gas strut, also known as a gas spring, uses compressed nitrogen gas to open furniture doors and flaps upwards in a controlled manner and hold them securely in position.

The correct installation of these components requires precision. A fixing point offset by just a few millimetres results in the flap either failing to close fully, not achieving the desired opening angle, or overloading the hinges. This technical guide is aimed at installers and experienced DIY enthusiasts, explaining the exact alignment, calculation, and installation of the fittings.

Preliminary Considerations: Choosing the Right Force in Newtons

Before beginning the installation, you must ensure that the existing fitting matches the furniture flap. The lifting force of these cylinders is specified in Newtons (N). A strut that is too weak will not keep the flap open, whilst a strut that is too strong will cause the flap to spring open uncontrollably and prevent gentle closing.

The rule of thumb for the calculation is: the weight of the flap in kilograms multiplied by 10 gives the approximate value in Newtons for one strut. For example, if an MDF front weighs 3.5 kg, you require a lifting force of around 35 N. Since struts are usually available in fixed increments (50 N, 60 N, 80 N, 100 N, 120 N), you select the next highest value – in this case, two 50 N struts to distribute the load evenly. For solid wood fronts or very large formats, gas struts for heavy flaps are used.

In general, it is advisable to use two gas struts per compartment for flap widths from 400 mm upwards. This prevents warping of the front and relieves stress on the upper concealed hinges.

Tools and Materials Required

The following tools are required for professional installation inside the carcase:

• Tape measure or folding ruler
• Precision pencil
• Bradawl or a thin wood drill bit (Ø 2 mm)
• Cordless screwdriver
• Suitable screwdriver or bit (usually PZ or PH cross-head)
• Chipboard screws (usually 3.5 x 15 mm or 4 x 16 mm, if not included in the scope of delivery)
• Two mounting brackets (one for the side panel, one for the front)
• The gas spring itself

Step-by-Step Installation Guide

The exact dimensions for the drilling points depend on the desired opening angle (usually 75°, 90°, or 110°) and the specific model. The following steps describe the universal procedure. Always consult the respective manufacturer's data sheet for exact millimetre specifications.

Step 1: Preparing the Carcase

The furniture flap must already be mounted to the top panel of the cabinet with the appropriate hinges and precisely adjusted. Ensure that the flap opens and closes smoothly before attaching any further flap fittings.

Step 2: Marking the Drilling Points on the Side Panel

The first fixing point is located on the inner side panel of the cabinet. Measure inwards from the front edge of the carcase (without the front). A typical dimension for a 90° opening angle is a distance of 250 mm down from the cabinet top and 20 mm in from the front edge. Mark the point for the first screw of the mounting bracket.

Step 3: Mounting the Carcase Bracket

Use the bradawl to make a slight indent at the mark in the chipboard. This prevents the screw from slipping when starting. Screw the mounting bracket securely in place using the appropriate chipboard screws. Ensure that the ball head of the bracket points inwards (into the cabinet interior).

Step 4: Marking the Drilling Points on the Flap

Now the counterpart is mounted on the inside of the flap. Measure downwards from the top edge of the flap (where the hinges are located). A common dimension here is approximately 90 mm. The distance inwards from the outer side edge of the flap depends on the position of the carcase bracket, ensuring the strut runs perfectly parallel to the side panel later on.

Step 5: Mounting the Flap Fixing

Make pilot indents for the screw holes here as well. With painted fronts or thin frame profiles, take extra care to ensure the screws do not break through the front face. Fasten the mounting plate securely.

Step 6: Inserting the Gas Strut

Now clip the cylinder onto the ball heads of the brackets. Engaging the ball head into the socket works much like hitching a car trailer onto a towbar – a distinct click signals a secure, positive fit.

Important: Always install the strut with the thick cylinder attached to the carcase (top) and the thin piston rod attached to the flap (bottom). This orientation ensures that the internal oil lubricates the seals on the piston rod when closed. If the strut is installed upside down, the seals dry out, the gas escapes, and the component loses its function.

Step 7: Functional Test

Close the flap slowly. Check whether the front sits flush with the carcase or if the strut is binding. Then open the flap again. Over the final few centimetres, it should move smoothly and automatically to the desired final angle (e.g. 90°) and remain securely in place.

Visual Integration in Cabinet Making

Modern hardware technology must not only be functional, but also visually suited to the piece of furniture. Whilst purely utilitarian fittings are often installed in a workshop or garage, aesthetics play a crucial role in living spaces and kitchens. Fittings can be matched to suit the respective interior finish of the cabinet.

For a classic white kitchen carcase, a white gas strut is recommended, blending visually with the back panel. In modern, dark designer kitchens or furniture in anthracite, a black gas strut provides a harmonious overall appearance without jarring contrasts. If you prefer a technical, industrial look or have stainless steel elements in the room, a silver gas strut is the ideal choice.

Particularly for wall cabinets above the sink, which are often additionally fitted with a dish draining rack for wall cabinets, flaps are frequently operated with wet hands. A reliable and visually appealing flap mechanism is essential here.

Common Installation Mistakes

Even experienced tradespeople occasionally make errors when installing pneumatic fittings. The following mistakes must be avoided:

1. Incorrect Cylinder Orientation: As mentioned in Step 6, installing the strut with the piston rod facing upwards is the most common cause of premature failure. The sealing rings become porous.
2. Asymmetrical Mounting: If two struts are installed on a wide flap, they must be positioned symmetrically to the exact millimetre. If the drilling points differ between the left and right, the flap will twist upon closing. In the long run, this leads to hinges tearing out of the chipboard.
3. Insufficient Screw Insertion Depth: If screws are too short, they cannot withstand the leverage forces exerted when closing the flap. The brackets tear out of the wood. Always use screws that penetrate deep enough into the material without protruding through the other side (e.g. 15 mm screws for an 18 mm thick front).
4. Confusing Components: A gas spring actively opens and supports a load. It must not be confused with a simple furniture damper (soft-close cylinder), which merely cushions the slamming of a door and possesses no lifting force.

Removal and Replacement of Defective Struts

After several years of intensive use, the pressure inside the cylinder may decrease. The flap will then no longer stay open on its own, but slowly sag downwards. In this case, the component must be replaced.

Removal is straightforward: at the ends of the strut (on the ball sockets), there is a small metal retaining clip or spring bracket. Slide a flat-blade screwdriver underneath this clip and pry it up slightly (about 2 to 3 mm). This releases the locking mechanism, allowing you to easily pull the strut off the ball head. The ball heads screwed into the furniture panels can usually remain in place, provided the replacement part is from the same manufacturer and has the same socket diameter.

Frequently Asked Questions (FAQ)

Can the force of a gas strut be adjusted retrospectively? No. The force in Newtons is permanently determined by the amount of nitrogen gas filled at the factory and cannot be regulated. If the flap is too heavy, a strut with a higher N value must be installed.

Are there alternatives to gas struts? Yes, mechanical flap stays (also known as lift-up supports). These operate with mechanical friction or springs instead of gas pressure. Their holding force is often adjustable, though they typically do not offer the same smooth movement profile as pneumatic cylinders.

What angle should the flap open to? This depends on accessibility. The standard is 90°, as the flap sits horizontally into the room and the handle remains easily reachable for people of average height. For very high wall cabinets, angles of 75° are sensible so the flap does not move out of reach. Angles of 110° are ideal for eye-level cabinets to provide a clear view into the carcase.

Why does my flap fail to close properly over the last few centimetres? This happens when the fixing points have been placed too close to the hinges. The strut does not have enough room to fully retract when closed and constantly pushes the flap slightly open. Check the dimensions in the installation instructions and, if necessary, move the carcase bracket backwards by a few millimetres.