How to Measure for a Roller Door
Ordering the wrong roller door size can quickly become an expensive problem. A door that’s too narrow simply won’t cover the opening, while an oversized door means paying for materials you don’t need. The key issue is that roller doors are not sized by the opening alone. You must also allow for the space required for guide tracks, the curtain roll, and the motor assembly.
In New Zealand, roller doors are specified by overall door size, not just the hole in the wall. The height is taken directly from the opening, but the width includes extra overlap into the side tracks—usually an additional 50mm to 100mm overall. Getting these figures right from the start ensures the door fits correctly and operates smoothly.
The good news is that you can measure for a new roller door yourself in about 20 minutes using basic tools. There’s no guesswork involved—just careful measuring of the opening and surrounding clearances.
This guide explains every step of the process. You’ll learn about common roller door size ranges in New Zealand, how to accurately measure your garage opening, what clearance space is required, and how to convert those measurements into a final door size ready for quoting or ordering.
What You’ll Need Before You Start
You don’t need any specialist equipment to measure for a roller door. Most homeowners already have everything required.
Essential tools
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Tape measure (minimum 5 metres, steel tape preferred)
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Notepad and pen or your phone for recording measurements
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Stepladder or stable platform to reach the lintel safely
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A second person to help hold the tape for wider openings
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Spirit level (optional, but helpful for checking if the opening is square)
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Torch if lighting inside the garage is poor
Before you begin, remove any stored items near the door opening so you can access the full frame. Always take three measurements for both width and height—garage openings are rarely perfectly square.
Step 1: Know Common Roller Door Size Ranges
Before measuring, it helps to understand how roller door sizing works in New Zealand. While doors are made to order, manufacturers price them in size brackets. For example, any custom width between 2551mm and 2800mm is charged at the 2800mm rate.
Knowing these common ranges helps you understand where your opening sits and how it may affect cost and lead times.
Single garage roller doors
A typical single garage roller door is around 2100mm high x 2400mm wide, which suits most standard residential garages. However, manufacturers commonly offer sizes from:
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Height: 1250mm to 3200mm
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Width: 1850mm to 3250mm
If your opening is close to standard dimensions, you’ll usually benefit from lower costs and quicker turnaround times. Consider vehicle height and width as well—SUVs, 4WDs, or roof racks often require extra clearance.
Double garage roller doors
Double garage roller doors are commonly around 2400mm high x 4800mm wide. Typical size ranges include:
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Height: 2400mm to 3300mm
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Width: 4200mm to 4800mm
Roller Doors wider than 4800mm are usually Shutter Doors and not suited to residential use due to the noise they make.
Step 2: Measure the Garage Opening
Because garage openings can shift and settle over time, measuring in multiple places ensures accuracy.
Measure the opening width
Measure the horizontal distance between the inner faces of the left and right jambs at three points:
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Just under the lintel (top)
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Halfway down (middle)
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At floor level (bottom)
Record all measurements in millimetres. For example:
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Top: 2405mm
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Middle: 2400mm
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Bottom: 2398mm
Use the largest measurement as your opening width. The door must cover the widest point to avoid gaps or exposed tracks.
Check for floor nibs, weather strips, or raised thresholds, as these can reduce usable width by 10–20mm per side.
Measure the opening height
Measure vertically from the finished floor to the underside of the lintel. If the floor slopes, measure from the highest point. If you’re keeping an existing floor seal, measure from the top of that seal.
While height is slightly more flexible than width, extra headroom above the opening allows for a taller door, improving the seal at the top and helping keep out dust, leaves, and pests.
Note any lights, pipes, or conduits below the lintel, as these can restrict usable height.
Step 3: Measure Required Clearances
A roller door needs more than just the right opening size. The hardware requires space on the sides, above, and behind the opening to function correctly.
Side room (left and right)
Side room is the horizontal space between the door opening and the nearest obstruction on each side. Measure from the inside face of each jamb to the closest wall, pipe, or fixture. Take measurements at multiple heights and record the smallest figure for each side.
Typical minimum requirements:
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Single doors: 100mm per side
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Double doors: up to 250mm per side
The motor side usually needs more clearance. Motors can typically be installed on either side, but you must specify this during ordering.
Headroom
Headroom is the vertical space above the opening, measured from the lintel to the first obstruction such as ceiling joists or roof framing.
Most standard roller doors require at least 400mm of clear headroom to accommodate the curtain roll, motor, and mounting brackets. Larger doors may require more.
Backroom (garage depth)
Backroom is the distance from the inside face of the opening back along the ceiling to the nearest obstruction. Measure straight back to the rear wall, shelving, or beams.
Most roller doors require 450mm to 600mm of backroom, depending on the door and motor type. Clear this area before installation to avoid delays.
Step 4: Confirm Your Final Door Size
Once all measurements are taken, you can determine the correct roller door size for ordering.
Use:
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The largest width measurement
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The largest height measurement
For example:
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Width: 2405mm
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Height: 2100mm
Your opening size is 2405mm wide x 2100mm high.
Measurement checklist
| Measurement | Dimension |
|---|---|
| Opening width | _______ mm |
| Opening height | _______ mm |
| Left side room | _______ mm |
| Right side room | _______ mm |
| Headroom | _______ mm |
| Backroom | _______ mm |
Confirm all clearances meet minimum requirements:
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Side room: 100mm (single) or up to 250mm (double)
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Headroom: 450mm minimum
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Backroom: 450–600mm
If any measurement falls short, address obstructions before placing your order.
Always rely on your smallest clearance measurements to guarantee the door will fit correctly.
Final Thoughts
You’ve now completed the full process of measuring for a new roller door. With accurate opening dimensions and confirmed clearances, you can confidently request quotes or place an order without risking installation problems.
When contacting a supplier, provide your finished opening size along with all clearance measurements. Most NZ manufacturers work from these figures to determine whether a standard-priced door suits your garage or if adjustments are needed.
If you’re considering installing the door yourself, check a dedicated DIY installation guide to decide whether it’s within your skill set and tools.
Accurate measurements upfront save time, money, and frustration later.