One of the most common questions we get at DoorsNZ is: "What size door do I actually need to order?" In New Zealand, the garage door industry uses a standard called Daylight Opening (DLO). This means you measure the hole in the wall (the opening), and we manufacture the door curtain to be slightly larger so it overlaps the back of the opening. This overlap ensures a weather-tight seal and keeps the "creepy crawlies" out.
If you are a DIYer, getting these numbers right is the difference between a smooth weekend install and a door that doesn’t fit. Here is our step-by-step guide to measuring like a pro.
1. The Golden Rule: The "Opening" vs. The "Door"
When you browse our Domestic Roller Doors, the sizes you see refer to the Opening Size.
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The Curtain is Wider: For a standard roller door, the actual steel curtain is usually 50mm to 100mm wider than the opening. This allows the door to sit inside the tracks (guides) hidden behind the door jambs.
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The Drum sits Higher: The rolled-up door sits above the opening. You must have enough "headroom" above the lintel for the door to disappear when open.
2. The 5 Key Measurements You Need
Grab a steel tape measure and a mate to help. Always record your measurements in millimetres (mm).
A. Opening Width
Measure the distance between the inside edges of the left and right jambs.
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Pro-Tip: Measure at the top, middle, and bottom. If your garage isn’t perfectly square, record the widest measurement.
B. Opening Height
Measure from the finished floor to the underside of the lintel.
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Note: Measure both the left and right sides. If one side is higher, record the tallest measurement.
C. Headroom (The "Roll" Space)
This is the space from the underside of the lintel to the lowest point of the ceiling (or rafters).
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Requirement: For a standard Garador Series 1 Roller Door, you generally need 350mm to 450mm of headroom.
D. Side Room
This is the flat wall space hidden behind the jambs where the tracks and motor will live.
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Non-Motor Side: Min 100mm.
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Motor Side: Min 250mm (to allow space for the Automatic Opener).
E. Back Room
Measure how far back into the garage the door can go without hitting a shelf, light fitting, or rafter.
3. Recommended Products for NZ Homes
Most Kiwi garages fall into these high-volume categories. Click the links below to see pricing for your specific size:
| Best For... | Recommended Product |
| Budget & Tight Spaces | Garador Series 1 Roller Door |
| Wider Double Garages | Windsor 240 Series Roller Door |
| Maximum Insulation | Insulated Sectional Garage Doors |
4. Frequently Asked Questions
Why is the garage door wider than the opening?
In New Zealand, roller doors are designed to overlap the opening on the inside. This overlap (usually 25mm–50mm per side) allows the door to run securely inside the vertical guides and provides a better seal against wind and rain.
What if my headroom is less than 350mm?
If you have limited space above the lintel, you may need a Mini Drum fitted to a Windsor 2200mm high Roller door or consider a Sectional Panel Door and add a "Low Headroom Kit", which can operate in tighter ceiling spaces than a traditional roller door roll.
Do I measure in cm or mm?
Always use millimetres (mm). Garage door manufacturing is precise; being "a couple of centimetres off" can lead to the door binding in the tracks or not closing flush against the floor.
Ready to get a quote?
Once you have your measurements, it is generally easy to order the door on the website or head over to our Quick Quote Page. You can even upload photos of your opening, and our technical team will double-check your clearances before you order.
Need help? Give us a call at 022 437 2652—we’re here to help you get the right door, first time.