Kallax Shelving: Compatible Inserts, Legs & Castors (Compatible with IKEA)

October 8, 2025

Compatible fittings for the IKEA Kallax shelving unit include precisely fitting inserts, furniture legs, and castors designed for the internal dimensions of 335 mm x 335 mm and the specific lightweight construction of the carcass. Due to the honeycomb core structure, installation requires special mounting plates or using the solid edge areas to ensure secure load distribution.

What exactly are compatible Kallax fittings?

The Kallax shelving system is based on a so-called board-on-frame construction. Whilst the internal partition walls are made of 15 mm thick chipboard, the 39 mm thick outer walls feature an internal honeycomb core made of paper. Only the outer 30 mm to 50 mm along the edges are solid.

When drilling, the lightweight wall behaves like an eggshell – a hard outer layer with a hollow core. Standard wood screws find no grip in the middle of the board. When retrofitting furniture legs or furniture castors, the mounting plates must sit precisely on the solid edges or be reinforced with a continuous base plate. For internal customisation with drawers or extra shelves, the exact grid dimensions are crucial.

Types of inserts and suitable fittings

To functionally expand the shelving unit, various hardware types are used:

Mobile bases: Swivel castors with and without brakes. They require a high load capacity, as the combined weight of the shelving and its contents concentrates on four or more points.
Standing feet: Metal furniture legs or black furniture legs are popular choices to visually elevate the unit. They are usually fixed with a flat mounting plate.
Additional shelves: To divide the 335 mm high compartments, 5 mm drill holes are placed into the side walls. Shelf supports or simple shelf brackets are used here.
Drawer inserts: Due to the shallow carcass depth, retrofitted drawers generally utilise roller drawer runners. These partial extension runners are compact and engineered for light loads.

Dimensions, standards, and typical values

When selecting fittings, the following technical parameters apply:

Internal compartment dimensions: 335 mm width x 335 mm height x 390 mm depth.
Material thicknesses: Outer frame 39 mm, internal dividers 15 mm.
Screw length: For the outer walls, chipboard screws (drive PZ or TX) must not exceed 35 mm in length to avoid piercing through the board.
Load capacity: A single shelf is rated for 13 kg as standard. When installing castors, each castor should feature a load capacity of at least 30 kg to 50 kg.

Installation, application & selection

Secure installation of legs or castors under the carcass requires preparation. Because the centre of the bottom panel is hollow, square furniture legs should be positioned flush in the corners where the frame is solid.

Alternatively, a 15 mm or 18 mm thick base plate (e.g. made of MDF) can be screwed or glued across the entire underside of the shelving unit. Any adjustable furniture legs can then be attached to this plate. Height adjustment helps level out uneven floors and align the unit perfectly upright. To protect delicate hard flooring against scratches, square felt pads can be applied under rigid feet.

Related terms

Lightweight board: A composite panel material with outer skin layers and a lightweight core material.
Honeycomb core: A stabilising paper insert with a hexagonal structure inside the furniture panel.
System 32: A standardised hole pattern grid (32 mm spacing) used in furniture construction, to which inserts also adhere.