Measuring without a ladder
Measure the footprint
Run a tape along the outside walls for the length and width. Pacing works too if you check your stride against a tape first.
Split awkward shapes
For an L or T-shaped house, treat each wing as its own rectangle, run the calculator for each and add them together. Include an attached garage if it shares the roof.
Pick the eaves
Look at how far the roof overhangs the walls and choose the closest option.
Judge the pitch
Stand across the street and compare the slope with the options. Membrane and skillion roofs are close to flat, and many villas are steep. If you have the house plans, the pitch is often marked on them.
What does the number tell you?
It gives the sloped area of a simple roof shape. Hips, valleys, dormers, extensions and sheet overlaps all add to what a roofer measures and orders, so expect their figure to come out higher than yours.
It doesn't tell you how hard the roof is to work on, and pitch matters there as much as size. WorkSafe says edge protection on roofs steeper than 25 degrees should be system-rated with infill panels, and above 35 degrees it should be specifically designed. That's one reason a steep roof can be a bigger job than a flatter one of the same area.
Pitch also limits what can go on top. Gerard's pressed metal tiles, for example, need a minimum pitch of 12 to 20 degrees depending on the profile, according to their BRANZ appraisal. Lower roofs usually suit longrun or a membrane instead.
Where the area comes in handy
Re-roofing and roof painting quotes are often worked out from the area, so it's a useful way to check two quotes describe the same roof. If one roofer's area is a long way off yours, ask how they measured it. A good roofer will happily explain.
It also settles one asbestos question quickly. A business removing more than 10 square metres of bonded asbestos needs a removal licence, and almost any house roof is bigger than that.
What we'd do with your figure
Keep it handy when the quotes arrive, and ask each roofer to put their measured area on the quote. If the numbers don't match, the conversation about why usually tells you more than the number itself. Our quote checker covers the rest of what a good quote should show.
Want a roofer to take a look?
Tell us the job and your postcode. We match it with a Find My Roofer certified roofer who specialises in that kind of work, and they call you to quote. Your number goes to them alone.