How To Measure A Garage Door Opening In Australia DIY Guide

How To Measure A Garage Door Opening In Australia DIY Guide

How To Measure A Garage Door Opening In Australia DIY Guide

Measuring a garage door opening isn’t just width and height with a tape and a guess. Order a door a few millimetres off, or overlook headroom for the drum or tracks, and your “quick DIY” turns into rework. Whether you’re replacing a tired door or planning a new build, getting accurate measurements — including side room, headroom and backroom — is the difference between a smooth install and a headache.

The good news: it’s straightforward with the right steps. This guide shows you how to measure like a pro for Australian conditions, accounting for the differences between roller and sectional doors, manual and automated operation, and common on-site quirks such as out-of-plumb jambs or sloped slabs. You’ll learn how to take multiple readings and use the smallest, and how to allow for opener clearances and vehicle height.

We’ll start with the tools and key terms, check if a standard Aussie size will suit, then work through each measurement in order: opening width and height, side room, headroom and backroom. We’ll help you assess squareness, spot obstructions, plan power for automation, confirm vehicle and driveway clearance, and record everything for a stress-free DoorSupply order. Let’s get measuring.

Step 1. Gather tools and understand key terms

Good measurements start with the right kit and a common language. Before you learn how to measure a garage door opening, set up safely and get clear on what’s what so your notes match your order and our factory specs. It also speeds up quoting.

  • Tools: tape measure, spirit level or laser, ladder, notepad/phone, camera, PPE, helper.
  • Key terms: opening width/height; side room (100/250 mm min single/double); headroom (above lintel); backroom (opening to rear obstruction).

Step 2. Check if your opening is the common Australian garage door size (single 2100 x 2400 mm; double 2100 x 4800 mm)

Before you go deep, do a quick sense-check. In Australia, common “standard” openings are roughly single 2100 mm high x 2400 mm wide and double 2100 mm high x 4800 mm wide. If your opening is close, great. If not, no drama — DoorSupply builds custom to size. Either way, keep measuring precisely to confirm clearances.

  • Single: 2100 mm (H) x 2400 mm (W)
  • Double: 2100 mm (H) x 4800 mm (W)

Step 3. Choose your door type and fit method (roller vs sectional; face fix vs reveal fix)

Door type and fixing method decide clearances and how you measure. Roller doors coil above the opening and typically need more headroom (~450 mm) with a side‑mounted opener. Sectional doors run back on ceiling tracks and need around ~350 mm, with a ceiling‑mounted opener. Decide now so, when you follow how to measure a garage door opening, your numbers match the system you’ll order.

  • Face fix: Door/track mounts to the wall face; keeps the full clear opening; can hide minor jamb imperfections.
  • Reveal fix: Door/track fits between jambs; reduces clear width/height; confirm side room for tracks and brackets.

Step 4. Measure the opening width (top, middle, bottom; use the smallest)

Measure the finished opening between the inner faces of the jambs in millimetres. Garage door tracks are rarely perfectly parallel, so take three readings — at the top, middle and bottom, — to capture any taper or bow. Use the widest measurement as the clear opening width. 

  1. Measure across the top of the opening; note Wtop.
  2. Measure across the midpoint; note Wmid.
  3. Measure across at floor level; check for nibs/strips; note Wbot.
  4. Determine the widest point as your recorded opening width and proceed.

Step 5. Measure the opening height (left, centre, right; use the smallest)

Measure the finished opening height from the floor to the underside of the lintel. Because slabs and lintels aren’t always square, take three readings — left, centre and right — and work to the largest. Note any floor slope and whether a weather strip or threshold will remain, as both affect the final clear height.

  1. Measure floor to underside of lintel at the left jamb; note Hleft.
  2. Repeat at the centre and right; note Hcentre and Hright.
  3. Check for an un‑level floor and any bottom strips you’ll keep/remove.
  4. Choose the largest measurement as your opening height.

Step 6. Measure side room on both sides (aim for 100 mm single, 250 mm double)

Side room is the clear space beside the opening that hardware needs for tracks, brackets and, on roller doors, the side-mounted opener. Australian guidance indicates a minimum of about 100 mm each side for single garages and around 250 mm each side for doubles. For reveal-fix, measure within the returns; for face-fix, measure the wall area beyond the opening. Note the first obstruction (wall, pipe, meter box) — not just the brick edge.

  1. Measure left: inner jamb to first obstruction; note Lside.
  2. Measure right: inner jamb to first obstruction; note Rside.
  3. Compare: single ≥ 100 mm each side; double ≥ 250 mm each side.
  4. If short, flag it now and consider face-fix hardware, relocating obstructions, or adjusting door type/size.

Step 7. Measure headroom above the opening (roller about 450 mm; sectional about 350 mm)

Headroom is the clear space above the lintel to the lowest obstruction (ceiling, beams, lights, opener). It determines whether a roller or sectional door will fit. As a guide, allow about 450 mm for a roller door and about 350 mm for a sectional door. Measure carefully so your chosen system and motor clear.

  • Measure lintel to lowest obstruction at left, centre, right; note HRleft, HRcentre, HRright.
  • Set HRmin = min(HRleft, HRcentre, HRright). Compare: roller ~450 mm; sectional ~350 mm. If short, note the deficit and plan adjustments.

Step 8. Measure backroom depth (door height + 500–1300 mm depending on opener)

Backroom is the clear depth from the inside face of your lintel to the nearest obstruction along the ceiling. For sectional doors, allow roughly door height + 457 mm for manual lift, or door height + 1270–1300 mm with an automatic opener. Use Required backroom ≥ Hmin + allowance.

  • Measure lintel to the rear obstruction along the ceiling (BR), then confirm BR ≥ Hmin + 457 mm (manual) or BR ≥ Hmin + 1270–1300 mm (auto). If short, relocate obstructions or choose a compact opener.

Step 9. Check squareness, plumb and floor level; note any corrections needed

Doors love straight, square openings. Real garages often aren’t, so before you finalise how to measure a garage door opening, confirm the jambs are plumb, the lintel is level and the slab isn’t sloping. Recording any irregularities now helps you plan packers or minor prep.

  • Plumb (jambs): Hold a spirit level against the left and right jambs from floor to lintel. Note any lean or twist and where it occurs.  You might need to order a slightly wider door if the jambs are not plumb
  • Level (lintel): Check along the underside of the lintel. Record if one side is higher; this affects track bracket positions.
  • Level (floor): Place a level across the threshold and along the opening. Note slope direction; keep any weather strip in mind.
  • Bows/bumps: Sight or use a straight‑edge across jamb faces and lintel to spot bows or nibs. Mark areas needing packers, grinding, or trimming.

Step 10. Identify obstructions and plan clearances (pipes, lights, doors, storage)

Before you lock in how to measure a garage door opening, scan for anything that could clash with drums, tracks, or the opener. Stand inside, look up, left and right, then open/close any internal doors or gates. Mark the lowest obstruction line on the wall — that becomes your hard limit for headroom and backroom.

  • Pipes/ducts/conduit: Relocate or adjust fixing method.
  • Lights/sensors: Move out of track and opener path.
  • Stairs/shelves/storage: Shift or trim to clear travel paths.
  • Swing doors/gates: Reverse swing or add stops.
  • Beams/bracing/meter boxes: Avoid mounting conflicts; preserve access.

Step 11. Plan for automation and power (opener type, power point location)

Automation choices affect clearances and where you’ll need power, so lock this in before finalising how to measure a garage door opening. Roller doors typically use a side‑mounted opener near the drum; sectional doors use a ceiling‑mounted opener behind the door when open. Confirm a safe, dedicated GPO nearby — avoid extension leads — and plan cable routing away from moving parts.

  • Roller door opener: Side-mounted at the drum; locate a GPO on the wall/ceiling close by and leave service access.
  • Sectional door opener: Ceiling‑mounted behind the lintel; place a GPO on the ceiling aligned with the rail; ensure backroom from Step 8.
  • Options: Consider battery backup, smart/Wi‑Fi control and safety beams; allow space for accessories and keep sensors clear of obstructions.

Step 12. Verify vehicle and driveway clearance (4WDs, roof racks, slopes)

When learning how to measure a garage door opening, also confirm your tallest setup fits. Measure your 4WD/SUV’s,RV's, Caravan or Boat overall height in everyday trim (lift, tyres, roof racks, pods, aerials, bikes) and compare with opening height from Step 5. Assess the driveway: steep slopes and transitions reduce effective clearance at the lintel. Ensure tailgates/boots and ute canopies can open under the door.

Step 13. Document your measurements with photos and a simple sketch

Lock in accuracy by documenting as you measure your garage door opening. Take clear, well‑lit photos with the tape in frame and label: left/right jambs, lintel, ceiling obstructions, and any GPO. Sketch a simple plan/elevation; mark Opening height and width, HRmin, BR, Lside, Rside, obstruction distances, slope arrows, and face/reveal fix.

Step 14. Convert your measurements into a DoorSupply order (door size, colour, wind rating, lock/auto)

You’ve learned how to measure a garage door opening; now translate those figures into a clean order so manufacturing is spot‑on and installation is simple.

  • Door type & fixing: Roller or sectional; face‑fix or reveal‑fix.
  • Door size: For reveal‑fix, order Wmin x Hmin. For face‑fix, supply clear opening size and fixing type; DoorSupply sizes guides/overlap.
  • Clearances: Provide HRmin and BR to confirm opener fit.
  • Colour/finish: Bluescope Colorbond colour or Zincalume.
  • Wind rating: Standard, Wind‑Strong or Wind‑Locked for exposed/high‑wind sites.
  • Operation: Manual with lock, or automatic with opener (Merlin, ATA, RD Motor, Grifco) and GPO location.

Step 15. Final pre-order checklist

Before you hit Order, run this quick sanity check so your made‑to‑measure door fits first time. If any item is a ‘No’, tweak the plan or ask DoorSupply to review before we cut steel.

  • Measurements: Opening Height x Opening Width in mm.
  • Clearances: HRmin, BR, side room OK.
  • Door & fix: Roller/sectional.
  • Opener & power: Model + GPO.
  • Site fit: Obstructions cleared; vehicle clears.
  • Spec: Colour, wind rating; photos/sketch.

Next steps

You’ve captured the right numbers, checked clearances, and mapped any fixes. Now turn those notes, photos and your sketch into an order. Decide roller or sectional, face or reveal, confirm opener and power, then lock in your colour and wind rating. If anything’s unclear, pause and recheck your smallest measurements before proceeding.

When you’re ready, order your Australian‑made, custom‑sized door and opener online, with DIY install guides and delivery to most major cities. Prefer a second set of eyes?

Share your measurements and site photos to us by email and we’ll sanity‑check them before manufacture. Start your order or get help at DoorSupply.