Clear height: what it means and why it decides everything
Clear height is the single most consequential dimension in an industrial bay. What it measures, where it is measured, and what each range of height allows.
How a bay is built
Loading: dock doors, grade doors and the choice between them
Dock versus grade loading, typical door sizes, levellers and ramps, and how to work out which configuration your operation actually needs.
Loading is the reason industrial space exists, and the loading arrangement is the hardest thing to change after you sign. A bay with the wrong doors can sometimes be fixed, but cutting a new opening in a tilt-up panel or a block wall is structural work with a permit attached.
Grade doors
A grade door, also called a drive-in door, sits at floor level. A vehicle drives straight in. This is the default in small-bay industrial and it is the right answer for most trades, service and light-assembly tenants.
- Typical opening: around 10 to 14 feet wide by 12 to 16 feet high in modern buildings; older stock is often smaller.
- Needs an apron outside with enough depth to swing and back — usually 60 feet or more of manoeuvring space for anything larger than a cube van.
- Loads and unloads at floor level, so you need a forklift with reach, a tailgate or manual handling.
- Cheapest to build, cheapest to heat, and the most flexible for mixed use.
Dock doors
A dock door sits at trailer-deck height so a trailer backs up flush and a forklift drives directly into it. Deck height is conventionally around 48 inches, but it varies with the trailer type.
- Typical opening: around 8 to 10 feet wide by 9 to 10 feet high — smaller than a grade door, because it only has to clear the trailer opening.
- Usually fitted with a leveller to bridge the gap and take up the height difference, plus bumpers and often a seal or shelter.
- Needs a deep apron. A 53-foot trailer needs a substantial depth of manoeuvring court in front of the door, and a shared court needs more.
- Essential for anyone shipping or receiving full trailer loads on a regular basis.
The compromises you will see in bays
| Arrangement | How it works | Watch for |
|---|---|---|
| Dock plus grade | One of each in the same bay. The most flexible small-bay configuration and the one that leases fastest. | Confirm both are usable at once — sometimes the apron only serves one. |
| Recessed or drive-down dock | A ramp drops down to a dock in an otherwise at-grade building. | Drainage and ice. A ramped dock well in Alberta needs a working drain and a heat trace or it becomes unusable in winter. |
| Dock leveller in a grade door | An edge-of-dock or portable leveller lets a grade door take a trailer occasionally. | A workaround, not a dock. Slow, and it needs the trailer to be at the right height. |
| Shared dock | A common dock serves several bays in the building. | Scheduling conflicts, and check the lease for who controls access and pays for repairs. |
How many doors do you need?
For most small-bay tenants, one door is enough and two is comfortable. The question is throughput: count your inbound and outbound vehicle movements at peak, and how long each occupies the door. If a single vehicle ties up the only door for an hour and you have four deliveries in that hour, you need a second door or a different schedule — not a bigger bay.
The loading throughput calculator puts numbers to that, using your own vehicle counts and turnaround times.
Things to check at the viewing
- Measure the clear opening of every door — not the frame, the actual clear width and height.
- Stand outside and look at the apron depth, the slope, and what happens when the neighbouring bay is loading at the same time.
- Check the door operator: chain hoist, or electric with a manual release? Is the safety edge working?
- Look at the header height inside the door — it often sets your real clear height near the loading area.
- In an Alberta building, look for a drain and heat trace at any depressed dock, and ask what happens in a February thaw.
Questions
Frequently asked
Can a grade door be converted to a dock?
Sometimes, by excavating a ramped dock well outside the door, but it is significant work — excavation, retaining walls, drainage, a permit, and the landlord's consent. It is far easier to find a bay that already has the loading you need.
What size grade door should I look for?
For vans and small trucks, a 12-foot-wide by 14-foot-high opening handles almost everything. If you need a tandem truck or a loaded trailer to enter, you are looking for 16 feet of height and a clear approach, which is uncommon in small bays.
Do I need a dock if I receive full trailer loads?
Almost always, yes — or a reliable arrangement with a neighbour. Unloading a 53-foot trailer through a grade door means either a portable leveller or unloading by hand, and both get old quickly if it happens weekly.
How a bay is built
All guides →More in this section
Floors, columns and structure inside a bay
Slab thickness and point loads, column grids, demising walls, drains and sumps — the structural facts that limit what you can put in a bay.
Put it to work
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