System 02 · The first density upgrade
Double deep racking: halve your aisles, keep your building.
Double deep places two selective bays back to back, so pallets are stored two positions deep and the number of aisles roughly halves. Floor utilisation typically rises from 30–40% to 45–55% inside the same walls. The price is selectivity: the rear pallet only becomes available once the front one has left, and you need a reach truck with telescopic forks.
In brief
Double deep racking places two selective bays back to back so pallets are stored two positions deep, roughly halving the number of aisles. It suits warehouses holding at least two pallets per SKU and requires a reach truck with telescopic forks.
- Around 40% more pallet positions than selective racking inside the same building.
- Only works when you hold at least two pallets of the same SKU — otherwise lanes sit half empty.
- A pantograph or telescopic-fork reach truck is mandatory; a counterbalance forklift cannot reach the rear position.
- Front and rear positions need separate location codes in your WMS, or the rear pallet becomes invisible stock.
01 — The qualifying test
Double deep only works if your stock profile allows it
This system rewards depth of stock per SKU and punishes variety. Run these four checks before going further.
You need at least two pallets of the same SKU to fill a lane cleanly. With an average of one pallet per SKU you will constantly store mixed goods in a lane and lose the density you paid for.
A double deep lane behaves as first-in-last-out within the lane. If every SKU is date-controlled with tight rotation, look at pallet flow instead.
A reach truck with pantograph (telescopic) forks is mandatory. A standard counterbalance forklift cannot reach the second position. Budget the truck alongside the racking.
Lane loading rules have to be followed. Density gained on paper is lost in a week if operators put whatever fits into whatever lane is open.
02 — Design specifics
What changes compared with a selective run
Deeper, tied frames
Two frame lines are connected with row spacers sized for the lane depth. The pair must be tied and anchored as one structure — the rear frame is far less accessible for later correction.
Higher beam elevations
Add clearance so the pantograph can lift the rear pallet clear of the front one. Beam elevations typically sit 100–150 mm higher per level than in an equivalent selective run.
Guards on both frame lines
Impact risk rises because the truck works deeper into the structure. Column guards on the aisle-facing uprights are the minimum; end frames need protection too.
Lane discipline and location codes
Front and rear positions need separate location codes in your WMS. Without them, the rear pallet becomes invisible stock — the classic double deep failure.
03 — Side by side
Selective, double deep, drive-in
| Criterion | Selective | Double deep | Drive-in |
|---|---|---|---|
| Lane depth | 1 pallet | 2 pallets | 4–10+ pallets |
| Floor used for storage | 30–40% | 45–55% | 60–80% |
| Selectivity | 100% | About 50% | Low |
| Rotation | FIFO or LIFO free | Tends to FILO | LIFO (drive-through: FIFO) |
| Truck required | Counterbalance | Pantograph reach truck | Counterbalance entering the lane |
| Impact risk to structure | Low | Low to moderate | High |
| Relative investment | Lowest | Moderate | Moderate |
Real warehouses usually mix systems: selective for fast-moving and low-depth SKUs, double deep or drive-in for the deep, homogeneous lines.
04 — Enquiry checklist
What to send us for a double deep design
- Heaviest pallet weight, pallet dimensions and pallet type (wood or plastic).
- SKU count and the average number of pallets held per SKU — the number that decides this whole design.
- Reach truck model, including mast reach, pantograph extension and residual capacity at height.
- Clear building height, column grid and floor area, plus slab thickness and grade.
- Whether your WMS can address front and rear positions separately.
Questions buyers ask
Frequently asked questions
How much extra capacity does double deep actually give?
Roughly 40% more pallet positions than selective racking in the same building, because the number of aisles roughly halves. The gain depends heavily on building width and column grid, so we model it on your actual floor plan rather than quoting a percentage.
Can I use my existing counterbalance forklift?
No. Reaching the second position requires a reach truck with pantograph or telescopic forks. If buying one is not realistic, selective racking or drive-in are the sensible alternatives.
Is double deep suitable for date-controlled products?
Only with care. Within a lane, the rear pallet is retrieved last, so stock rotation depends on lane discipline. For strict date rotation, pallet flow racking gives true first-in-first-out without operator judgement.
Does double deep need a different beam capacity?
The beam capacity is the same per level as an equivalent selective bay, but the pantograph handling and higher clearances change beam elevations and total frame height. The structure is checked as a tied pair, not as two independent runs.
Can existing selective racking be converted to double deep?
Sometimes. If frame heights, beam capacities and the slab allow, we can re-space existing runs and add row spacers and additional frames. We inspect the existing structure first and report anything that should not be re-erected.
What lead time should I plan for?
Fabrication typically runs three to four weeks after drawing approval, similar to selective racking. Allow additional time if you are also procuring a reach truck, which is often the longer lead item.
Talk to engineering, not a call centre
Send your SKU list and pallet weights. We will tell you if double deep pays.
We model your current selective layout against a double deep layout and show the pallet position count for both, so the decision is made on numbers rather than on a brochure.