Fitting Deep Eaves Cupboards: Full Extension Drawer Runners for Maximum Space Utilisation

A full extension runner allows a drawer to be pulled 100% out of the carcass, ensuring complete access to the rear storage space, especially in deep cupboards under sloping ceilings.

An eaves cupboard makes use of the low space beneath a sloping roof. Due to their design, these cupboards often feature an above-average depth, frequently reaching 600 mm to 800 mm. Shelves are impractical at such depths, as items stored at the back become difficult to reach. The eaves cupboard behaves like a deep tunnel – without the right runner technology, the back remains in the dark. The solution is fitting deep drawers. For joiners and ambitious fitters, this raises the question of the exact technical configuration of the fittings.

This guide defines the essential criteria for selecting the right runner system to equip deep eaves cupboards in a mechanically stable and ergonomically practical way.

Key Purchasing Criteria for Eaves Cupboard Runners

When planning deep drawers, installation dimensions, mechanical load limits, and the carcass geometry must be precisely aligned.

1. Nominal Length and Installation Depth

The nominal length of the runner defines the length of the fitting in the closed position and generally corresponds to the outer drawer depth. The internal carcass depth must be at least equal to the nominal length plus a tolerance allowance (usually 3 mm to 5 mm). For deep cupboards, long runners are essential. A common dimension for sloping ceiling solutions is drawer runners 600 mm. If structural constraints mean the eaves space is slightly less deep, drawer runners 500 mm or drawer runners 400 mm are used instead.

2. Load Capacity and Leverage

The deeper the drawer, the more contents it holds, and the greater the leverage effect when fully extended. Standard runners are typically designed for 25 kg to 30 kg. For a drawer depth of 500 mm or more carrying heavy contents (tools, thick winter clothing, files), this is often insufficient. In this case, heavy duty runners are required. Heavy duty drawer runners offer load capacities of 45 kg, 80 kg, or even up to 130 kg. The dynamic load capacity must always cover the self-weight of the drawer plus the maximum payload.

3. Extension Type: Full Extension vs Single Extension

A single extension runner only releases the drawer to approximately 75%. In a 600 mm deep drawer, around 150 mm would remain hidden inside the carcass. For eaves cupboards, this is impractical. A full extension runner is mandatory here, extending the drawer box completely past the front edge of the carcass. Specific full extension drawer runners feature a three-part telescopic mechanism that reliably supports this overhang with mechanical stability.

4. Side Clearance and Space Requirements

The side clearance is the exact gap between the inside of the carcass and the outside of the drawer. For standard side-mounted ball bearing runners, this dimension is standardly 12.7 mm per side. The outer drawer width is therefore calculated from the internal carcass width minus 25.4 mm. If this dimension is not maintained to the millimetre, the runner will bind or the ball bearings will sustain damage.

Overview of Types and Options

The choice of runner technology determines the running action and the mounting method.

Ball Bearing Runners vs Undermount Runners

The ball bearing runner is screwed to the side of the drawer or recessed into a groove. It consists of steel profiles in which ball cages run. It is extremely robust, available in very long lengths, and tolerates minor installation deviations. The undermount runner is fitted concealed beneath the drawer base. It provides a cleaner aesthetic and often excellent running properties. Undermount drawer runners do, however, require a specific drawer construction (extended side panels, notched back panel) and take up more space in height. An older alternative is the roller runner. Roller drawer runners operate using nylon rollers. They are simple to fit but usually offer only single extension and lower load ratings, making them less suitable for very deep eaves cupboards.

Soft-Close vs Push-to-Open

These two convenience functions are based on opposing mechanical principles and must not be confused during planning.

• Soft-Close: An integrated hydraulic damper catches the drawer over the final centimetres and pulls it shut gently and silently. Drawer runners with soft close are ideal for bedrooms or heavy drawers where slamming must be prevented.
• Push-to-Open: A spring mechanism ejects the drawer when light pressure is applied to the front. Push to open drawer runners enable handleless fronts, which is often desirable in modern built-in cupboards under slopes.

Which Runner for Which Application?

To streamline the selection, consider the following technical configurations:

• When the cupboard is used for heavy items (bedding, lever arch files, tools) and has a depth of over 500 mm: Select side-mounted heavy-duty ball bearing runners with at least 45 kg load capacity as a full extension.
• When a handleless, minimalist aesthetic is required in the bedroom: Select runners with a push-to-open mechanism. Ensure that the trigger travel (usually 2 mm to 3 mm) is accounted for when setting the front gap.
• When the cupboard is in a children's bedroom or living area and loud slamming must be avoided: Select runners with self-closing mechanisms and damping. Self-closing drawer runners actively pull the drawer into the closed end position over the final 30 mm to 50 mm.
• When high-quality timber drawers are used and the side panels should remain visible: Select undermount runners. The hardware remains completely hidden.

Installation Guidelines for Deep Eaves Cupboards

Fitting long runners requires precision, as angular deviations multiply over the full length.

Required Tools:

• Cordless drill/driver
• Bits: PZ (Pozidriv) or TX (Torx) size 2
• Tape measure or folding rule
• Try square
• Spirit level
• Bradawl or 3 mm wood drill bit

Installation Steps:

1. Marking out: Mark the horizontal position of the runners inside the carcass. Where possible, use the System 32 grid if the carcass features corresponding line boring. The hole pitch is precisely 32 mm, and the standard distance from the front edge is 37 mm.
2. Fastening the carcass profile: Separate the inner runner part (drawer member) from the outer part (carcass member) – with ball bearing runners, this is usually done via a small plastic release lever. Screw the carcass member to the internal side panel. Use chipboard screws (countersunk, Ø 3.5 mm or 4 mm) or dedicated Euro screws if 5 mm line boring is present. Ensure exact parallelism.
3. Fitting the drawer profile: Screw the inner member to the side of the drawer box. The front edge of the profile sits flush with the drawer front (or the carcass of an internal drawer).
4. Engagement: Align the drawer with the fitted inner members precisely level with the carcass members. Push the drawer in with gentle pressure until the ball cages click audibly into place.

FAQ – Frequently Asked Questions About Drawer Runners

What is the exact difference between full extension and single extension? A full extension runner allows the entire drawer depth to be pulled out (100% travel). A single extension runner stops at the rear quarter, meaning the drawer can only be pulled out by around 75% of its length. For deep cupboards, full extension is technically superior.

Can I combine soft-close and push-to-open? Mechanically, these are opposing systems (damping/braking vs spring/ejection). As standard, these functions are mutually exclusive in a single runner. Hybrid systems exist on the market, but they require specialised synchronisation rods and precise front gap calculations.

How do I determine the correct runner length for my eaves cupboard? Measure the internal carcass depth (from the inside face of the back panel to the front edge of the side panel). Deduct 5 mm to 10 mm from this figure. The result is the maximum nominal length. For example, if the carcass is 615 mm deep, select a runner with a 600 mm nominal length.

Which screws do I need for fitting ball bearing runners? For engineered timber such as chipboard or MDF, use chipboard screws with a diameter of 3.5 mm or 4.0 mm. The length depends on the carcass material thickness (usually 16 mm or 19 mm) – 3.5 x 15 mm is typically used. The countersunk head must sit completely flush in the runner hole so that it does not obstruct the ball carriage.

Why is my deep drawer sticking when pulled out? When long drawers jam, it is usually due to a lack of parallelism. Either the carcass is out of square, or the side clearance of exactly 12.7 mm per side was not maintained. On deep runners, a deviation of just 1 mm to 2 mm causes significant binding in the ball cage.