Gas Struts & Flap Stays: Matching Replacements for Wall Unit Flap Doors

A gas strut assists the opening of furniture flaps using compressed nitrogen gas and holds the front securely in the open position, whereas a mechanical flap stay operates via friction or spring tension.

Wall units with upward-opening flaps are standard in kitchens, living room wall units, and office furniture. When the flap of an overhead cabinet – such as those from common furniture stores – no longer stays up after some time or falls shut on its own, the fault is almost always due to pressure loss in the gas strut. A complete replacement of the hinge system is not necessary. Replacing the strut cartridge is a standard mechanical procedure that can be carried out quickly with accurately sized replacement parts.

This guide explains the technical specifications that must be considered when selecting replacement flap fittings to ensure proper operation and consistent gap alignment.

Key Purchasing Criteria for Replacement

A gas strut is a wear part. To find the exact matching replacement, three technical parameters must be read from the old part or calculated afresh.

1. The Extension Force in Newtons (N)

The force with which the cylinder pushes the flap upward is specified in Newtons. Typical values for standard furniture flaps are 50 N, 60 N, 80 N, 100 N, 120 N, or 150 N. This value is usually printed on the cylinder housing of the defective strut (e.g. "100N"). If the print is illegible, the following rule of thumb applies for calculation: 10 N corresponds to a lifting capacity of around 1 kg. If the furniture flap weighs 8 kg including the handle, an 80 N strut is required. For wide flaps supported by two struts (left and right), the required force is divided. In this case, an 8 kg front requires two struts of 40 N to 50 N each.

2. The Installation Dimension (Length)

The length of the strut is measured in its fully extended state. The relevant dimension is the distance from hole centre to hole centre between the two ball socket mountings. Common dimensions in furniture construction are 245 mm, 247 mm, or 268 mm. A deviation of 1 mm to 2 mm can usually be compensated for by the adjustability of the mounting plates; larger deviations drastically alter the opening angle of the flap or prevent it from closing.

3. Fixing Type and Ball Head Diameter

The connection between the strut and the carcase is generally made via a ball joint. The ball head on the mounting plate usually has a diameter of 10 mm. The mounting plate itself is screwed to the carcase, often matching the System 32 standard (32 mm hole spacing, 37 mm distance to the front edge). When simply replacing the strut, the old mounting plates remain screwed into the cabinet; only the cylinder is unclipped from the ball heads.

Overview of Flap Fitting Types

Depending on the weight of the front and the desired kinematics, different flap fittings are used.

Standard Gas Struts

These consist of a pressure tube and a piston rod. They assist the opening process and gently brake at the end of the stroke. They are suitable for standard fronts made of chipboard or MDF with a melamine coating.

Heavy-Duty Flap Fittings

For very large fronts, flaps made of solid wood, or heavy aluminium-glass frames, the standard version is often insufficient. In these cases, gas struts for heavy flaps are used, which deliver extension forces of 150 N up to 250 N. For extreme weights, robust, purely mechanical lever kinematics are often utilised.

Mechanical Flap Stays

A mechanical flap stay operates without gas pressure. It uses adjustable friction to hold the flap open in any chosen position (intermediate stop). These fittings suffer less wear and tear, but require more manual effort when opening the front.

Which Fitting for Which Case? (Decision Guide)

The choice of the correct replacement part depends strictly on the weight of the front and the structure of the carcase.

• If the front is a lightweight standard flap (approx. 600 mm width, 300 mm height) made of 16 mm chipboard, then two struts rated at 50 N to 60 N each are usually sufficient.
• If it is a large kitchen wall cabinet front (e.g. cladding above a dish drying rack for wall units), then forces between 80 N and 120 N are required.
• If the interior appearance of the cabinet is also to be upgraded during the repair, then colour matching to the decor is recommended. Available options include gas struts in silver, gas struts in black for dark wood decors such as Wotan oak, or discreet gas struts in white for white carcases.
• If you are looking for a replacement for a brand-specific lifting system, then check compatibility with established systems such as LIFT-O-MAT, whose mounting points often serve as an industry standard.

Installation: Replacing the Gas Strut on a Wall Unit

Replacement works like changing a car tyre – the system must be relieved of tension, the old component is removed, and the new one is simply clicked into place.

Required Tools:

• Flat slotted screwdriver (small)
• Tape measure or callipers
• Crosshead screwdriver (PZ 2) only if the mounting plates also need replacing.

Step-by-Step Instructions:

1. Secure the flap: Open the cabinet flap completely and have a second person or a support hold it in this position. The system must be free of tension.
2. Release the retaining spring: At the ends of the old strut, there is a small metal clip (retaining spring) enclosing the ball head. Slide the flat screwdriver under this clip and lever it slightly open (do not remove it completely).
3. Pull off the strut: The strut can now be pulled sideways off the ball head of the mounting plate.
4. Fit the new strut: The new strut is simply pressed onto the existing ball heads until it audibly clicks into place. Prying the retaining clip is usually not necessary when pushing it on.
5. Note the mounting orientation: The thicker side (the cylinder) should point upwards when the cabinet is closed. This allows the internal oil to collect at the seal, ensuring smooth end-position damping during opening.

If the fronts are also to be refreshed aesthetically as part of the repair, this is the ideal time to fit matching drawer handles and wall unit handles.

Frequently Asked Questions (FAQ)

How do I calculate the required Newton rating for my flap? The rated force is usually printed on the housing of the old strut. If not: weigh the dismantled flap including the handle. 1 kg of weight requires about 10 N of lifting force. When using two struts per flap, divide the total weight by two.

Can I install a stronger strut so that it lasts longer? No. An over-dimensioned strut pushes the flap upwards with excessive force. Over time, this tears the screws of the concealed hinges out of the chipboard and makes closing the flap extremely difficult. The Newton rating must match the weight precisely.

How do I measure the length of the strut correctly? Measure in the fully extended, unloaded state. The correct measurement is the distance from the centre of the lower ball socket to the centre of the upper ball socket.

Why does my flap slam shut even though the strut is new? Gas struts are lifting aids, not closing dampers. They brake the flap during opening. For a smooth, silent closing of the front, the fitted hinges (concealed hinges) must have integrated soft-close damping.

Do standard replacement parts fit cabinets from popular retail brands? Yes. Most mass-produced furniture uses standardised fittings. As long as the installation dimension (e.g. 245 mm) and the mounting fixture (10 mm ball head) match, the struts are cross-brand compatible.