All articles · 7 min read

What's the difference between scanning and drawing a home?

A scan measures the home as it stands. A drawing reproduces the home as you understood it. Both can produce a measured floor plan — the difference is who decides what's there.

The two methods, side by side

Scanning: you hold up the phone and walk slowly along the walls. A rangefinder in the camera island sends out pulses of light and registers how far away everything it sees is. The software assembles the points into walls, doors, windows and furniture. You don't decide where the wall is — you discover it afterwards.

Drawing: you drag a rectangle on a sheet of graph paper on the screen, and that's a room. You type the room's measurements in centimetres, place doors and windows on the walls where they sit, and build the home up room by room. Everything on the drawing is something you put there yourself.

HouseSense offers both routes, and they end up in the same place: a home in the app with floors, areas, a floor plan, a 3D model, a takeoff and reports. The plus button simply asks which way you want to go in.

What a scan catches that a drawing doesn't, on its own

A scan is a measurement of reality, and reality is rarely square. That's what makes scanning strong:

• Crooked walls. A room that is 3.60 m at one end and 3.68 m at the other looks perfectly square to the eye. The scanner records the difference; you don't.
• Alcoves, chimney breasts and other projections. The small ledge behind the door, the pier between two windows, the chimney breast that juts 30 cm into the kitchen. They cost square metres and they cost flooring — and they're easy to forget when you draw from memory.
• Doors and windows in their real position. Not "roughly in the middle", but exactly where they sit, and at the width they actually are.
• How the rooms sit relative to each other. The scan knows the bedroom lies behind the bathroom, not beside it, because you walked there with the phone in hand.
• Ceiling height. It's measured along with everything else, without you climbing onto a chair.

The real gain isn't accuracy alone. It's that a scan has no opinion about what the home should look like. It takes what's there.

What a drawing can do that a scan can't

A drawing isn't a fallback for when LiDAR is missing. It can do four things a scan never will:

• It works without being there. You can draw a home from an estate agent's listing, from an old floor plan in a folder, or from a tape measure and a notepad. You don't have to stand in the house.
• It works on any iPhone and iPad. No LiDAR required, and no Pro model.
• It can draw what doesn't exist yet. The wall you're considering removing, the extension you're dreaming of, the converted loft. A scanner can only measure what's already standing.
• It's easy to correct. A number is a number. Need the room 20 cm wider? Type a different number — there's no scan to redo.

And a drawing isn't imprecise just because it's drawn. The measurements are just as valid as a scan's, if you measured them with a tape measure. HouseSense's paper reckons in whole centimetres and in internal measurements — from wall surface to wall surface, exactly how you'd measure a room yourself.

Who decides what's there?

That's the only difference that really matters. Everything else follows from it.

With a scan, the sensor decides, and you're the editor afterwards: you correct names, remove what it misread, decide which rooms belong to which floor. With a drawing, you decide the whole way through, and there's no sensor to speak up if you forget a pier.

Hence the rule of thumb: if you're in the home, scan. If you're not, draw. And if you're in the home and draw anyway, bring the tape measure — it's cheaper than guessing.

The arithmetic: why internal measurements don't match the official area

Both a scan and a drawing in HouseSense work in internal measurements. Official property registers and most estate agent listings, on the other hand, state the area externally, including the outer walls — that's how it works in most countries. So your own figure is nearly always smaller, and neither one is wrong.

An example you can follow: a house that measures 8.00 × 10.00 m externally is 80 m² on paper. If the outer wall is 35 cm thick all the way round, the internal measurement becomes 8.00 − 0.70 = 7.30 m and 10.00 − 0.70 = 9.30 m. 7.30 × 9.30 = 67.9 m². A good 12 m² has vanished into the wall — and the internal walls haven't even taken their share yet.

It's the internal figure you need when buying flooring, paint or heating. It's the external figure the authorities know. Both are correct; they just don't measure the same thing. If you're unsure what officially applies to your home, the property register and the local authority have the answer — not an app.

What the two methods share, once the home is in

Once the rooms are in place, there's no difference between a scanned and a drawn home in HouseSense. Both give you:

• area per room and for the whole home, floor by floor;
• a floor plan with measurements, exportable as a PDF;
• a takeoff for contractor quotes — wall area, floor area, ceilings, number of doors and windows;
• a 3D model you can walk around inside;
• sunlight based on the home's real address and north orientation, if you place the house on the map;
• budget and reports, and sharing with a buyer via a link.

It all lives in your own iCloud. There's no account to create and no server that gets a copy.

Accuracy: what actually shifts the number

Neither method has one fixed accuracy figure, and you should be sceptical of anyone who promises you one. What shifts the number is easy enough to understand, though:

For a scan: how steadily you walk, how good the light is, whether the walls are covered by cupboards and curtains, and whether you made it all the way round every wall. A room where three out of four walls are hidden behind shelving is one the scanner can only guess at — it doesn't see the masonry, it sees the shelving.

For a drawing: how carefully you measured, and whether you measured in the right place. Always measure at about 1 metre height, not at the skirting board, measure two spots in a room you're suspicious of, and enter the smaller figure if you're using it to order something that has to fit.

Both routes improve the same way: someone checking afterwards. A floor plan that hasn't been checked against a single tape measure is a guess in tidy packaging.

Can you use both in the same home?

Yes, and it's often the smartest choice. Scan the rooms you can get into, and draw the ones you can't: the locked storeroom, the cold garage, the loft with the three steps. The rooms live side by side in the same home, and the areas add up across the board.

It works the other way too. If you scanned, and there was an alcove the scanner made a mess of, you can correct it on the drawing board afterwards, instead of rescanning the whole floor.

So what should you choose?

Scan when you're in the home, have LiDAR in your phone, and are pressed for time — for example at an open house, where you have a quarter of an hour and will never come back.

Draw when you're sitting at home with an old floor plan, when the phone has no LiDAR, when the home is empty or inaccessible, or when you want to draw something that isn't built yet.

Do both when the home is big and messy: scan most of it, and draw the rest in once you've got the tape measure out.