🚛 What is a Truck Bay?
A truck bay (also called a truck loading dock) is a recessed or lowered area adjacent to a building that allows trucks to safely reverse in and load or unload goods at floor level.
In civil site design, a truck bay typically:
Sits below the surrounding carpark level
Interfaces directly with a building edge
Often requires retaining support
May be designed to either:
Drain normally, or
Temporarily hold water during extreme storm events (e.g. 100-year flood)
From a grading perspective, a truck bay introduces a controlled vertical split between the building platform and surrounding pavement.
How to Design a Truck Bay in Allsite (Level AI Workflow)
This guide explains how to model a truck bay using Allsite features before running Level AI.
Step 1 – Add a Grade Break Along the Building Edge
The truck bay must start with a grade break placed along the edge of the building where trucks will dock.
This grade break defines the vertical control between:
The building finished floor level
The truck bay platform level
Important Setting:
On this building-edge grade break:
Set Minimum Height Left
Set Maximum Height
These two values define the height difference between the building and the truck bay
Make sure maximum height is slightly larger than minimum height (4 inches / 0.1m is enough) - this gives Level AI ability to iterate
In practice, these define the depth of the truck bay
Set Snap Direction away from the building
Think of this as telling Level AI:
“The surface on the left side of this line must be equal to this height difference.”
Step 2 – Add Perpendicular Grade Breaks
To properly split the truck bay level from the surrounding carpark, you must add additional grade breaks perpendicular to the building.
These:
Extend outward from the building
Define the vertical separation between the truck bay and surrounding pavement
For These Perpendicular Grade Breaks:
Set Maximum Height
Optionally set Snap Direction depending on where you want the split wall in relation to the truck bay area.
Do NOT set “Maximum Height Left”
These act as vertical control limits but do not define a directional height like the building-edge break does.
Step 3 – Define the Truck Bay Area
Now define the physical area of the truck bay using either:
Impervious Area, or
Choose based on your site
In some designs (particularly large industrial sites), truck bays may be allowed to:
Temporarily hold water during a 100-year storm event
If this is acceptable
Set Allow Depression to true.
If this is not allowed leave it unset (default behaviour prevents depression)
This setting directly affects how Level AI handles low-point behaviour
Step 5 – Run Level AI
After defining:
Building edge grade break (with Max Height Left)
Perpendicular grade breaks (with Max Height only)
Impervious or Ground Control polygon
Depression setting (if required)
Run Level AI.
Step 6 – Review the Generated Feature Lines
After Level AI completes:
Inspect the generated feature lines
You will see the truck bay defined as:
A lowered platform
Cleanly split from the surrounding carpark
Retained at the building edge
These feature lines represent the resolved grading solution.
📐 Typical Truck Bay Geometry
Typical characteristics:
Recessed slab area
Vertical face or retained edge at building
Transition ramp or break to surrounding carpark
Controlled drainage flow path
⚙ Key Design Rules Summary
Element | Required Setting |
Building Edge Grade Break | Maximum Height Left = Truck Bay Height |
Perpendicular Grade Breaks | Maximum Height only |
Truck Bay Area | Impervious or Ground Control |
Allow Water Ponding | Set Allow Depression = True (if permitted) |
💡 Practical Design Tips
Ensure perpendicular grade breaks extend far enough to prevent blending with surrounding carpark grades.
Confirm the truck bay height matches architectural dock height requirements.
If using Allow Depression, validate downstream stormwater design.
Always inspect generated feature lines before final surface rebuild.