Choosing Forklift Lift Height: Matching Stacker Height to Your Racking

Rack height is not lift height. Order a stacker that reaches exactly the top beam and the forks will hit it on every put-away. This guide shows how to convert your racking into the right specification, and how mast stages change what fits under your roof.

1. Lift height is not the same as rack height

The number on the racking drawing is the height of the steel. The number you order is the height the forks reach, and those two are not the same figure.

When a pallet goes in or out of a beam level, the forks must travel above the beam before the pallet clears it, then come down onto the supports. That extra travel is clearance. On most warehouse racking, plan on the rack top beam height plus 150-300 mm. Below 150 mm you will scrape beams, especially with a loaded pallet that sags or a pallet whose bottom boards sit low. Above 300 mm you are buying mast you do not need, and paying for it in lost capacity.

Two practical details decide where you land in that 150-300 mm band:

• Pallet condition. Damaged or uneven bottom boards need more room to slide over the beam. Add toward the upper end.
• Operator tolerance and floor levelness. A wide aisle with a level floor allows tighter clearance; a worn floor in an older building usually does not.

So if your top beam sits at 4,500 mm, you are shopping for roughly 4,650-4,800 mm of lift, not 4,500 mm.

2. Rack height to lift height: the working numbers

The table below covers the common bay configurations we quote most often. It assumes 1,500-1,800 mm between beam levels and a 150-300 mm clearance margin.

Treat this as a starting point, not a rule. Beam spacing drifts when a warehouse adds a level later, and a building survey is the only way to confirm the real numbers.

3. How mast stages change the choice

Mast stages determine both how high the forks go and how tall the machine stands when the mast is collapsed. That second number is the one that catches people out.

• Duplex mast. Two mast sections. The collapsed height is only slightly less than the lift height, so a 5 m duplex stands about 3.5-4 m tall when lowered. Simple, strong, and usually the cheapest route to a given lift height. It needs vertical room at the rack face, which is fine outdoors or in a high bay.
• Triplex mast. Three sections. It lifts higher from a shorter collapsed mast, so a truck with 6.5 m of lift may stand only about 2.5-3 m lowered. This is what you use when the rack is taller than the doorway, or when sprinkler pipes and lighting run across the aisle.
• Triplex full-free lift. The forks rise on their own before the mast sections extend. This is the arrangement for work under a fixed ceiling, and it is the standard choice for loading containers, where the door header limits how far the mast can rise before the forks enter. Without full-free lift, a container door height of about 2.3 m will stop a conventional mast well short of the load.

If you are loading containers at floor level and also putting pallets away at 6 m, one full-free triplex truck can do both jobs. Two single-purpose machines usually cannot.

4. How to choose

Work through these steps in order. Each one can eliminate a model before you get to pricing.

• Measure the rack top beam, not the rack height. Take the distance from the floor to the top face of the highest beam you will actually use. Add 150-300 mm for clearance. Write that number down as your required lift height.
• Measure building clear height, including obstructions. Sprinkler heads, light fittings, cable trays and roof trusses all reduce usable height. A 9,000 mm eaves height with sprinklers at 8,100 mm gives you a working limit of about 8,100 mm, and often less after the required sprinkler clearance.
• Check the mast lowered height against every door you cross. A 6.5 m triplex might stand 2,900 mm lowered, which clears a 3,200 mm door but not a 2,800 mm one. Measure the lowest opening on the truck's route, not just the main aisle.
• Check collapsed height against the rack beam you pass under. Mast sections extend upward as the forks rise, so the truck's working height at full lift is the lift height plus roughly 300-600 mm of mast. A 5 m lift needs about 5.3-5.6 m of clear air.
• Confirm capacity at height, not at the data plate. A truck rated 2,000 kg at 500 mm load centre may be rated 1,200 kg at 6,000 mm, and less with a 600 mm load centre. Check the capacity chart for the exact lift height you specified.
• Match fork length and spread to the pallet. Standard 1,150 mm forks suit a 1,200 x 800 mm pallet; a 1,200 x 1,000 mm pallet usually needs 1,150-1,220 mm forks. Adjustable fork spread helps if you handle mixed pallet sizes.
• Confirm the aisle width. A 6.5 m reach truck typically works in a 2,800-3,000 mm aisle; a counterbalance truck of similar capacity needs 3,500-4,000 mm. If your aisle is 2,600 mm, the truck choice is already made for you.
• Check the floor and the wheel load. High-lift trucks concentrate load on the mast and front wheels. Confirm your floor slab and any mezzanine or trailer ramp can take the point load.

5. Common mistakes

• Ordering lift height equal to rack height. No clearance means damaged beams and damaged pallets. Add the 150-300 mm.
• Forgetting the sprinklers. A truck that fits the rack but not the building is an expensive mistake found on delivery day.
• Ignoring capacity loss at height. The data plate figure is measured at low lift. Read the derating chart.
• Buying a taller mast "for the future". A taller mast adds weight, costs capacity, and often needs a stronger floor. Add racking levels only after you have checked the building clear height.
• Overlooking the container door. Standard container doors are around 2.3 m. Non-full-free masts will not load them properly.
• Measuring one bay instead of the highest bay. Racking runs vary. Survey the tallest point in the run you will actually use.

6. FAQ

What lift height do I need for 6 m racking?

Specify about 6,500 mm. The 500 mm margin covers the 150-300 mm entry and exit clearance plus the fork and pallet thickness that sits above the beam.

Is lift height the same as mast height?

No. Lift height is how high the forks travel. Mast height is how tall the truck stands, and it changes as the mast extends. A triplex mast with 6,500 mm of lift may stand only about 2,900 mm when collapsed.

Why choose a triplex mast instead of a duplex?

A triplex mast lifts higher from a shorter collapsed profile, which matters when sprinklers, doorway headers or container doors limit headroom. A duplex is simpler and usually cheaper when vertical space at the rack face is not restricted.

What is a full-free lift triplex mast for?

The forks rise before the mast sections extend, so the load enters a low opening such as a container door or a low-clearance rack level without the mast hitting the header first.

Does lift height reduce how much I can carry?

Yes. Capacity drops as lift height increases because the load centre moves further from the mast. A truck rated 2,000 kg at low lift may be rated 1,200-1,500 kg at 6,000 mm. Always check the chart for your exact height.

How much clearance do I need above the top beam?

Plan on 150-300 mm from the top beam to the required lift height. Use the upper end of that range for damaged pallets, uneven floors or inexperienced operators.

Can one truck handle both container loading and 6 m racking?

Often yes, if it has a full-free lift triplex mast and enough capacity at 6 m for your heaviest pallet. Confirm both the lowered height for the container door and the derated capacity at the top level.

7. Related products

• Electric reach trucks
• Electric stackers
• Special applications: explosion-proof and cold store trucks
• Forklift attachments
• Customized series