Retrofitting Drawers for IKEA Besta

A full-extension runner extends to 100%, whereas a partial-extension runner only moves the drawer box out by around 75% in front of the cabinet.

Anyone wishing to expand the functionality of an existing cabinet carcass often plans to add drawers at a later date. Modular furniture ranges provide a strong foundation for this. If you are retrofitting drawers and looking for fittings compatible with IKEA Besta, precise planning regarding installation dimensions, runner types, and fixing techniques is essential. This technical guide is aimed at installers and experienced trade professionals who require accurate tolerances and mechanics to achieve clean shadow gaps.

What to Consider Regarding Compatibility

Retrofitting drawer systems into existing furniture carcasses is primarily a question of geometry. The cabinet carcass determines the maximum available space for the fittings.

System 32 and the Hole Pattern

Industrially manufactured cabinet components are generally based on System 32. This means the vertical lines of holes in the side panels have an exact drilling distance of 32 mm between them. The distance from the front edge to the first line of holes is also standardised at 37 mm. Fittings used as alternatives to IKEA components use this exact grid pattern to secure the cabinet runner. Check beforehand whether the existing carcass has pre-drilled holes with a 5 mm diameter (for Euro screws) or if you need to pre-drill the positions for chipboard screws yourself.

Installation Depth and Runner Length

The usable depth of the cabinet is the critical dimension. A standard unit in the mentioned range has an external depth of 400 mm. Subtracting the thickness of the back panel and the front leaves an internal clear depth of around 380 mm. The fitted drawer runners must be shorter than this measurement.

In practice, installers use nominal lengths of 300 mm or 350 mm. If drawer runners 300 mm are installed, for example, sufficient room remains behind the drawer box for air circulation or potential cable routing.

Choosing the Right Mechanism

The cabinet runner serves as the backbone of the entire assembly and defines the operational feel. Depending on the intended use and the weight of the contents, different technical principles are employed.

Extension Type: Full or Partial?

For maximum access to the rear section of the drawer box, a full-extension runner is the technical standard. Full-extension drawer runners consist of three telescoping profiles that guide the drawer box completely clear of the cabinet front edge. For lower accessibility requirements, a partial-extension runner suffices, which by design leaves roughly a quarter of the box inside the carcass.

Runner Type: Ball Bearing or Undermount?

• Ball bearing runner: These runners are mounted to the sides of the drawer box. Smooth running is achieved using small steel balls inside a ball cage. They require exactly 12.7 mm of installation clearance on each side between the drawer box and the inner carcass wall.
• Undermount runner: This mechanism is concealed beneath the drawer base. The side panels of the drawer hide the runners. However, this requires a specific drawer box construction (notched back panel, recessed base).

Closing Mechanisms: Physical Contrasts

A frequent planning error is confusing closing mechanisms. These two systems are physically incompatible and cannot be combined within the same runner:

1. Push-to-Open (also known as Tip-On): A mechanical trigger activated by pressing the front panel. A tensioned spring pushes the drawer open slightly. Push to open drawer runners require handleless fronts and a trigger gap of approx. 2 mm to 3 mm between the front and the cabinet carcass.
2. Soft-Close: A hydraulic or pneumatic damper. Soft-close drawer runners absorb the momentum of the closing drawer and gently, silently pull it closed over the final centimetres. A furniture handle is strictly required to open the drawer against the resistance of the damper.

Installation and Retrofitting: Technical Steps

Proper installation requires precision. A deviation of just a few millimetres can cause a ball bearing runner to bind.

Required tools:

• Cordless screwdriver
• Screwdriver with PZ (Pozidriv) or TX (Torx) drive
• Tape measure or folding rule
• Try square
• Bradawl or pencil

Step-by-step installation:

1. Mark heights: Mark the desired drawer positions inside the cabinet. Ensure adequate spacing between individual front panels (a reveal gap of 2 mm to 3 mm is standard).
2. Mount carcass runners: Align the runners with the front line of holes (37 mm from the edge). If 5 mm holes are present, use Euro screws (e.g. 6.3 x 13 mm). For blank panels, use countersunk chipboard screws (e.g. 3.5 x 16 mm or 4 x 16 mm). The screw head must not protrude past the metal profile, as this will block the carriage mechanism.
3. Attach the drawer profile: Disconnect the inner profile of the ball bearing runner using the release lever. Screw this exactly along the centre line of the drawer side flank.
4. Insert and adjust: Slide the drawer horizontally into the cabinet runners until the mechanism audibly clicks into place. Check for smooth operation.

Additional Interior Accessories

Once the runners are successfully installed, the interior setup can be upgraded. To minimise items sliding around when opening and closing, adding an anti-slip drawer mat is recommended. These structured plastic mats also dampen noise and protect the melamine base from scratches.

If sensitive documents or tools are stored in the retrofitted modules, adding a locking mechanism is advisable. A drawer lock (typically a surface-mounted lock or a cam lock) requires a through-hole in the front panel. The cylinder diameter is typically 19 mm or 22 mm. When rotated, the locking cam engages behind the carcass shelf or into a separate strike plate.

FAQ: Retrofitting Furniture Fittings

Which runner length fits IKEA Besta carcasses? As the usable internal depth of the standard carcass is around 380 mm, nominal lengths of 300 mm or 350 mm are technically compatible. A 400 mm runner will collide with the back panel and cannot be fitted.

Can I use Soft-Close and Push-to-Open simultaneously? No. The systems operate using opposing forces. Soft-Close decelerates movement and pulls the front flush to the carcass. Push-to-Open relies on a spring pushing the front away from the carcass. You must choose one mechanism or the other.

Which screws do I need to mount the runners? If using the existing System 32 with 5 mm pre-drilled holes, flat-head Euro screws (6.3 mm thread diameter) are required. If screwing directly into solid board (chipboard/MDF), use chipboard screws with a diameter of 3.5 mm or 4 mm and a length of 15 mm to 16 mm.

Why is my full-extension runner jamming after installation? Jamming is usually caused by incorrect installation width tolerances. A standard ball bearing runner requires precisely 12.7 mm of clearance on each side. If the drawer box is too wide (clearance < 12.7 mm) or too narrow (clearance > 13 mm), the ball cage will bind and the runner will lose its smooth glide.