Sideboard Drawers Compatible with Blum Fittings: Retrofitting Soft-Close

January 17, 2026

Retrofitting soft-close to sideboard drawers requires precision drawer runners that match the existing carcase systems in installation width, nominal length, and load capacity.

Upgrading a piece of furniture with damping is a technical process that demands precise measurement and an understanding of the existing hardware engineering. Particularly when dealing with established standards, such as systems from the manufacturer Blum, an alternative or retrofitted runner must fit precisely into the existing drilling and milling pattern. A sideboard – whether as a 100 cm wide variant in the living room or as a compact model with a 35 cm depth in the hallway – benefits mechanically to a great degree from a damped closing mechanism. This reduces material stress on the carcase and prevents drawer fronts from slamming shut.

The drawer runner acts much like the chassis of a vehicle: it determines the smoothness of movement, directional stability under load, and the precise braking distance before the end stop. In this buying guide, we define the technical parameters that are decisive when choosing compatible runners for replacement or retrofitting.

The Main Buying Criteria for Retrofittable Runners

To convert a drawer from standard movement to soft-close, simply screwing on an external damper is rarely sufficient. As a rule, the entire drawer runner is replaced. The following strict criteria apply.

1. Nominal Length and Carcase Depth

The nominal length (NL) of the runner defines the depth of the drawer extension. It must match the existing drawer and is specified in millimetres. The carcase must always be slightly deeper than the nominal length of the runner (usually NL + 3 mm to 15 mm, depending on the manufacturer).

For a narrow sideboard with a 30 cm depth, runners with a nominal length of 250 mm or 270 mm are usually used. Here, drawer runners 250 mm are suitable for concealed or side-mounted installation.
For standard depths of 40 cm to 45 cm, one typically relies on drawer runners 350 mm or drawer runners 400 mm.
For deeper storage furniture in the bedroom or office, lengths such as 450 mm or 500 mm are the standard.

2. Installation Width and Internal Clearance

The clear carcase width (internal cabinet dimension) minus the external width of the drawer box gives the installation space required for the runners.

For side-mounted ball-bearing runners, this dimension is strictly 12.7 mm per side as standard.
For concealed undermount runners (such as Blum Tandem or Movento), the drawer side thickness is decisive. These systems are usually designed for drawer side panel thicknesses of 11 mm to 16 mm or up to 19 mm.

3. Load Capacity

The dynamic load capacity indicates how much weight the runner can permanently carry in its extended state without the profile warping.

For lightweight drawers in a small sideboard, 25 kg to 30 kg is sufficient.
For wide drawers (e.g. in an 80 cm or 100 cm wide sideboard) holding heavy crockery or files, 40 kg to 50 kg is required.

4. Extension Type: Full Extension vs. Single Extension

A full extension runner can be pulled 100% out of the carcase. The back of the drawer sits flush with the front edge of the cabinet. A single extension runner leaves approximately 25% of the drawer inside the cabinet. For maximum access right to the back of the drawer, drawer runners full extension are the technically superior choice, although they require longer telescopic profiles.

Overview of Drawer Runner Types

When retrofitting damping systems, installers generally encounter three basic types of runner construction.

Undermount Runners

These runners sit concealed beneath the drawer base. Systems from Blum (Tandem) are based on this technology. If you want to upgrade to damping here, you require compatible undermount drawer runners. The drawer rests on rear hooks and is secured at the front by a locking device (clip). When replacing with alternative manufacturers, it is essential to check whether the new runner is supplied with its own locking devices, as these locking mechanisms are often manufacturer-specific.

Ball-Bearing Runners

Ball-bearing runners are screwed to the sides of the drawer or recessed into a groove (usually 17 mm or 27 mm). They consist of interlocking steel profiles with ball cages. Upgrading to drawer runners with soft-close is relatively simple here, provided the lateral installation gap of 12.7 mm is present.

Roller Runners

These simple, powder-coated runners with plastic rollers are often found in older or very basic furniture. Roller drawer runners do not feature integrated damping due to their design. To achieve soft-close here, the roller runner must be completely removed and replaced with a ball-bearing runner or an undermount runner (including modifying the drawer box).

Which System for Which Scenario? (Decision Guide)

The choice of the correct runner depends on the current setup of the sideboard:

If the sideboard is currently fitted with undamped undermount runners (e.g. Blum Tandem single extension), then choose an undermount runner with soft-close in the exact same nominal length. Ensure that the position of the rear retaining pins matches.
If the piece of furniture has side groove runners (17 mm), then switching to modern ball-bearing runners with damping is recommended. The groove in the wooden drawer is covered by the runner profile.
If you want to equip a very deep sideboard (e.g. 50 cm) with full extension, then select drawer runners 450 mm with an integrated soft-close cylinder.
If the drawer is handleless, then you require push-to-open. Note: This is the mechanical opposite of soft-close. Soft-close pulls the drawer shut over the final few centimetres and brakes it. Push-to-open pushes it open when pressure is applied to the front. Combinations of both are mechanically complex and require specialised synchronisation mechanisms.

Installation Advice for Fitters

Replacing drawer runners requires precision. A deviation of just a few millimetres can lead to rough running or cause the damper mechanism to bind.

Tools Required:

Cordless screwdriver with PZ2 bit
Folding rule or vernier calliper
Bradawl or 5 mm wood drill bit (for System 32)
Try square

Installation Steps:

Removal: Remove the drawer. For undermount runners, release the front locking devices and lift the drawer off. Unscrew the old carcase runners.
Check Drilling Pattern: Check whether the carcase features System 32 drilling (32 mm hole spacing, 5 mm hole diameter). If this is the case, the new runners can be fastened using Euro screws (usually 6.3 x 13 mm). Without system holes, use chipboard screws (pan-head, 3.5 x 15 mm) or wood screws.
Alignment: The carcase runner must be installed perfectly level. The setback from the front edge of the carcase is usually 2 mm for overlay fronts.
Drawer Installation: For undermount runners, replace the locking devices on the underside of the drawer. Place the drawer onto the runners and push it in until the locking devices audibly engage.
Adjustment: Use the adjustment wheels on the locking device for height adjustment (usually +3 mm) and tilt adjustment to achieve consistent gap alignment across the front panels.

(Note: If you wish to dampen the sideboard doors in addition to the drawers, we recommend replacing the hinges at the same time with concealed hinges / cabinet hinges with damping (Soft Close).)

FAQ – Frequently Asked Technical Questions

Can I retrofit soft-close to a roller runner simply using an add-on damper? An add-on damper brakes the front, but it does not provide active self-closing across the entire path. For smooth and proper closing, the entire roller runner must be replaced with a ball-bearing runner featuring an integrated soft-close cylinder.

Are all undermount runners compatible with Blum locking devices? No. The locking devices and the rear positioning hooks vary between manufacturers. If installing an alternative to Blum, always use the locking devices supplied in the set with the new runners and replace them on the drawer box.

Which runner length do I need for a 35 cm deep sideboard? The internal carcase depth minus the back panel is usually around 320 mm to 330 mm here. The appropriate nominal length for the runner in this case is 300 mm.

Why is my newly installed soft-close drawer stiff to close? This occurs when the installation clearance (internal width) has not been strictly maintained. On ball-bearing runners, too little clearance (under 12.7 mm per side) puts excessive pressure on the ball cage. On undermount runners, carcase runners that are not mounted exactly parallel are often the cause.

What is the difference between self-close and soft-close? A basic self-close mechanism pulls the drawer shut over the last few centimetres using a spring, but does not decelerate it (meaning it slams shut). Soft-close combines this spring with an oil or gas hydraulic damper that absorbs the kinetic energy, closing the drawer gently and silently.

Matching Products & Categories for Your Project

For a professional sideboard conversion, you will find the right technical components across the following categories:

For concealed installation on wooden drawers: Undermount drawer runners
For complete access to the entire drawer interior: Drawer runners full extension
For side mounting with an integrated damping cylinder: Drawer runners with soft-close
For compact hallway furniture: Drawer runners 250 mm
For standard chests of drawers: Drawer runners 400 mm