A raised dock or a level entry: it is a slope calculation, not a habit
Every distribution project reaches the same argument: raised dock platforms with dock levellers, or a level floor with a ramp at the door. It is usually settled by preference, or by what the last project did.
It should be settled by two things that can be measured before anything is drawn: the slope of the site, and the vehicle mix that will actually arrive. Those two numbers decide most of the square metres, all of the earthworks and a good part of the floor structure.
Site slope decides more than traffic does
A raised dock exists to bring the warehouse floor up to the height of a truck bed. If the site already falls in the right direction, that elevation can come from the ground rather than from a structure, and the dock becomes cheap.
If the site falls the other way, a raised dock means filling or building up at the door and cutting elsewhere, and the earthworks can exceed the cost of everything above the slab. That is the point at which a level entry with an internal ramp starts to look reasonable and a raised dock looks like an expensive habit.
The useful first drawing is therefore not the warehouse plan. It is a site section through the door, showing existing levels, finished levels, the truck bed height, and the length available for a ramp or a dock face. That single section answers the question before the plan is fixed.
Ramp length is a geometry problem with a fixed answer
A ramp has one honest dimension: the height it has to climb, and the gradient that vehicles can use safely in the weather the site actually has.
A truck bed sits roughly 1.1 to 1.3 m (3.6 to 4.3 ft) above the ground. To climb that at a gradient of 1 in 12 requires about 14 m (46 ft) of ramp, and at 1 in 10 about 12 m (40 ft). Those are the numbers that eat the site: a ramp of 14 m plus the transition at each end plus the vehicle standing area in front of the door consumes 25 to 30 m (80 to 100 ft) of yard depth before anything is stored.
On a site where that depth does not exist, the choice disappears — the dock platform is the only option, whatever the preference was. On a site where the depth exists and the ground falls away, the ramp is often the cheaper build, but it takes land that could have been yard.
Wet climates tip the argument. A ramp that is usable in the dry season and a skid pan in the wet season is not a ramp; it needs a surface, drainage at its foot and enough gradient margin to compensate for a wet surface.
Dock height and the vehicle mix
A raised dock is only efficient if the vehicles that arrive are the ones it was built for.
Dock height is set from the bed height of the dominant vehicle. The vehicle mix then decides the leveller: a fleet of similar vehicles needs a small adjustment range, while a mix of small delivery vehicles and large articulated units needs a leveller with a wide range plus a lip that reaches into the smaller vehicle.
What the mix also decides is whether a dock is needed at all for part of the traffic. Many facilities end up with raised docks for the large vehicles and a level door with a ramp for the small ones, and that combination is often better than trying to serve everything from one platform.
Level entry: what it costs in drainage and in land
A level entry is not free of engineering. It moves the problem.
The floor has to be at yard level, which means the warehouse slab is at the lowest point of the site rather than above it, and drainage becomes critical rather than convenient. Water that would have run off a raised dock now runs toward the door, and a door that is not protected by a fall, a threshold and a canopy becomes the entry point for the wet season.
The advantage is the vehicle interface: no leveller, no restraint, no gap, and a forklift that drives straight in. For operations with high door traffic and mixed vehicles, that is worth a lot.
The other cost is land. A level entry needs the yard to be at the slab level, which on a sloping site means earthworks somewhere else — usually at the far end, where the yard has to be cut down to meet the building.
The transition zone is where vehicles get damaged
Whichever option is chosen, the transition is where the damage happens.
On a ramp, it is the top and bottom: a change of gradient that is too abrupt scrapes a bumper or grounds a low trailer, and the fix afterwards is a patch that makes the gradient worse. On a dock, it is the gap and the lip: a leveller that does not reach, a bumper that is too high or too low for part of the fleet, and a vehicle that reverses into the dock face because there is nothing telling the driver where to stop.
Both are solved by detail rather than by structure: a proper vertical curve at each end of the ramp, guide rails and a wheel stop at the dock, and dock bumpers positioned from the actual fleet rather than from a catalogue default.
What I want before drawings
- A site section through the door with existing levels, finished levels and the yard depth available.
- The vehicle mix: bed heights, lengths, and how often each type arrives.
- Whether vehicles reverse in or drive through, and who guides them.
- The rainfall pattern, because it decides the ramp surface and the drainage at its foot.
- Whether the yard will be paved, and where water leaves the site.
- The wind speed to be used, taken from the applicable code at the project site rather than a round number, plus the door and canopy detail — a large door opening on a windy site is loaded internally, and the threshold is where water and wind arrive together.
A dock and a ramp are the same decision seen from two directions: how much height, and how much length. Measure both before choosing, and the argument disappears.
Written by Johnny Joe, who advises owners and project managers in Africa and South America on steel buildings. If this decision is live on a project, send the layout and the constraint that worries you and I will tell you what it changes.
Related: a container freight station layout · a mezzanine inside a warehouse · what drives the cost · a truck loadout canopy
