Retrofitting Internal Wardrobe Drawers: Full-Extension Runners for Better Organisation

An internal drawer with a full-extension runner can be pulled 100% out of the carcass, whereas a partial-extension runner only reveals around 75% of the depth.

Introduction: Correctly Retrofitting Internal Drawers in Wardrobes

Retrofitting internal drawers in existing wardrobes is one of the most effective methods to utilise unused storage space. Particularly in deep wardrobes, fixed shelves prevent direct access to items of clothing stored at the back. For joiners and experienced fitters, the task is to select the right runner system based on carcass dimensions, required load capacity, and existing door hinges.

This guide covers the technical parameters for selecting the correct drawer runners. The focus is on distinguishing runner types, determining the exact installation dimensions in millimetres, and resolving typical installation obstacles, such as colliding door hinges.

Key Purchasing Criteria for Drawer Runners

The choice of mechanism determines the durability and function of the internal drawer. The following parameters must be clearly defined prior to installation.

Nominal Length and Wardrobe Depth

The nominal length of the runner must match the internal clear depth of the wardrobe carcass. For a standard wardrobe with an external depth of 600 mm and a grooved back panel, the internal clear depth is usually around 560 mm. A runner with a length of 500 mm or 550 mm is typically used here. For shallower carcasses, such as those with an external depth of 500 mm, the choice will be correspondingly shorter. A safety clearance of at least 5 mm to 10 mm from the back panel must always be planned.

Load Capacity in Kilograms

Clothing, especially folded winter jumpers or jeans, creates a substantial amount of weight. Standard runners are designed for dynamic loads of 30 kg to 45 kg. This is generally sufficient for conventional clothing drawers. With extra-wide drawers (from 800 mm carcass width) installed in large bespoke wardrobes, standard runners reach their limits. In such cases, using more robust systems is essential to prevent sagging or jamming.

Installation Width and System 32

The side installation clearance is the measurement between the inside of the carcass and the outside of the drawer. For classic telescopic runners, this measurement is exactly 12.7 mm per side. Carcass construction in furniture manufacturing is usually based on System 32. This means that the rows of holes for shelf supports and runners feature a vertical spacing of 32 mm, and the front row of holes is positioned 37 mm from the front edge of the carcass. Runners standardised to this system can be fixed directly into the row of holes using Euro screws without additional measuring.

Types and Options Overview

The market offers various mechanical concepts for drawer runners. Each design features specific structural characteristics.

Ball-Bearing Runner

The ball-bearing runner consists of interlocking steel profiles in which steel balls run within ball cages. It is mounted to the side of the drawer or set into a groove in the drawer side. This design is extremely rigid and is ideal for use as full-extension drawer runners. It offers high lateral stability, even with wide drawers.

Undermount Runner

With the undermount runner, the mechanism is mounted invisibly beneath the drawer base. The drawer sides completely conceal the runner. This variant offers very smooth running performance and is predominantly used in high-end furniture making. However, it requires precise drawer construction, as tolerances are tighter than with side-mounted runners. Undermount drawer runners are fixed via locking clips at the drawer front, enabling tool-free height and tilt adjustment.

Roller Runner

The roller runner is the simplest and oldest design. Plastic rollers run along epoxy-coated steel profiles. It is forgiving during installation, but usually offers only partial extension and has greater lateral play. For basic, lightweight internal drawers, a roller drawer runner is often sufficient, but it is less recommended for deep wardrobes due to the restricted access.

Additional Mechanical Features

Two main convenience features dominate the market, yet they operate on opposing mechanical principles:

1. Soft-Close: An integrated hydraulic damper catches the drawer across the final centimetres of closing. A spring then pulls the drawer smoothly and quietly into the carcass. Such drawer runners with damping require a classic furniture handle or a recessed grip to open.
2. Push-to-Open: A spring-loaded plunger triggers when pressure is applied to the front, ejecting the drawer a few centimetres from the carcass. This enables handleless fronts. Corresponding push-to-open drawer runners (also known as Tip-On) are ideal for a minimalist design inside the wardrobe.

Which System for Which Application?

The decision for a specific runner depends strictly on the structural conditions of the wardrobe and the intended contents.

• If the wardrobe is very deep (e.g. 600 mm):

  You must choose a full-extension runner. Only then can you reach the rearmost items of clothing without having to lift the front stack.

• If extra-wide internal drawers (over 800 mm) are planned:

  Opt for heavy-duty drawer runners. These provide load capacities of 60 kg or more and prevent the runners from yielding under the weight of the laundry.

• If you prefer handleless internal fronts:

  Use a system with push-to-open. As space inside the wardrobe for protruding handles is often limited, this solution saves valuable millimetres in depth.

• If you want to avoid building your own wooden drawer sides:

Use pre-assembled drawer systems. These consist of metal drawer sides into which only a 16 mm thick base panel and a back panel need to be fitted. The runner technology is already precisely matched to the drawer side.

Installation Notes for Internal Drawers: The Hinge Issue

A drawer runner behaves like a vehicle chassis – if the alignment is not accurate to the millimetre, the mechanism jams. When retrofitting within wardrobes fitted with hinged doors, there is one main source of error: the door hinges.

A standard concealed hinge (usually with a 35 mm cup hole) protrudes into the interior of the carcass. If an internal drawer is installed at exactly the same height, or needs to slide past the open door (with hinges having a 95° or 110° opening angle), a collision will occur.

Solutions:

1. Spacer strips: Fit a spacer strip on the hinge side between the carcass wall and the drawer runner. This bridges the projection of the hinge arm (usually 25 mm). The drawer must be built correspondingly narrower.
2. Wide-angle hinges: Replace existing hinges with wide-angle hinges (155° or 165°) with zero protrusion. With these hinges, the opened door swings completely clear of the internal carcass opening.
3. Positioning: Plan the heights of the internal drawers so that they run precisely between the existing concealed hinges.

For installation, mark the positions in System 32 using a set square. Securing the runners in the carcass on chipboard (16 mm or 19 mm) is ideally done using Euro screws (Ø 5 mm) in pre-drilled 5 mm holes, or with 4x15 mm panhead chipboard screws.

FAQ – Frequently Asked Technical Questions

What runner length do I need for a wardrobe depth of 50 cm? For an internal clear carcass depth of just under 500 mm (minus the back panel), a nominal length of 450 mm is the technically correct choice. This gives the runner sufficient clearance at the rear. Suitable models can be found under 450 mm drawer runners.

Can soft-close and push-to-open be combined in a single runner? No, this is mechanically excluded on standard runners. Soft-close uses spring tension to pull the drawer permanently inwards, while push-to-open relies on opposing spring tension that pushes outwards. Highly complex hybrid systems exist for premium kitchens, but within standard fittings for wardrobes, you must choose one of the two mechanisms.

What is the exact difference between full extension and partial extension? A partial extension stops after approximately 75% of the runner length. On a 500 mm long runner, around 125 mm of the drawer remains inside the carcass. A full extension features a third runner profile (telescopic), allowing the drawer to be pulled out across the full 500 mm clear of the carcass.

Why is my newly installed ball-bearing runner jamming? Ball-bearing runners have a tolerance of less than 1 mm. If the clear carcass dimension is 560 mm, for example, the drawer must be exactly 534.6 mm wide (560 mm minus twice the 12.7 mm installation clearance). If the drawer is just 2 mm too wide or too narrow, the ball cages will bind, causing the runner to operate stiffly or lose ball bearings.

Which runner length is suitable for very deep bespoke wardrobes? For non-standard depths, such as in walk-in wardrobes beneath sloped ceilings, the clear dimension can be well over 500 mm. In these cases, nominal lengths of 500 mm are used, available under 500 mm drawer runners, or longer versions up to 800 mm if required.

Matching Products & Categories

To turn theory into practice, you need fittings tailored exactly to your dimensions. Select the category according to your determined carcass depth and required functions:

• Full-extension drawer runners – For complete access to all wardrobe contents.
• Undermount drawer runners – For concealed mounting beneath the wooden base.
• Drawer runners with damping – For silent closing of heavy laundry drawers.
• Heavy-duty drawer runners – For extra-wide carcasses and load capacities beyond 45 kg.
• Drawer systems – Complete drawer side kits for quick assembly without making your own wooden sides.