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How do I prepare my home so the scan is as accurate as possible?

Five minutes of preparation removes most of the errors a scan can make in the first place. Here is the checklist — and the order to walk the home in.

Why preparation matters more than technique

Nearly every error that ruins a LiDAR scan of a home comes from the room, not the phone: a mirror, a glass door, a bookcase in front of a wall, a dark room. All four can be removed in advance. None of them can be fixed afterwards without going back and measuring again.

That makes five minutes of preparation the cheapest precision there is. It costs nothing and works on any phone with LiDAR.

The checklist: five minutes before you start

1. Turn on every light — throughout the home

Including rooms you only walk through, and even in the middle of the day. LiDAR measures distances fine in the dark, but the phone uses the camera image to track its own position — and a dark image has few details to recognise. If a room has no ceiling light, bring in a work lamp or switch on a floor lamp.

2. Cover the mirrors

A towel over the bathroom mirror, closed mirrored wardrobe doors. A mirror bounces the LiDAR light onward instead of back, so the scan measures the distance to the reflection and builds a phantom room behind the wall. It is the single error that causes the wildest results in a home scan — and it takes ten seconds to remove.

3. Draw curtains across large windows

Clear glass lets a good part of the light straight through, so the patio door either disappears or gets measured as the hedge outside. A drawn curtain is a matte surface in roughly the right plane. If you are scanning in the evening, this matters even more: dark outside and light inside turns the window into a mirror.

4. Open every internal door

Open doors give the phone a view into the next room before you get there, which makes the transition between rooms more reliable. Open wardrobe doors too, if the wardrobe should count as a room — and close them if it shouldn't.

5. Pull furniture away from the walls that matter

You don't need to empty the home. But pull the sofa, bed or bookcase 15-20 cm away from the wall in any room where the measurements will be used for something that costs money. That gives the phone a clear strip of wall to measure, and stops the front edge of the furniture from being read as the wall.

Two extra minutes, if the measurements will be used for quotes

• Remove rugs from the floor in rooms getting a new floor — the edge of a rug can create a false floor level.
• Dry glossy floors if they are wet. A wet surface behaves like a half-mirror.
• Switch off flat screens. A black, glossy screen in standby is both reflective and light-absorbing. Fully off, it's just a dark surface.
• Clear loose items off the floor, so you can walk steadily all the way round without stepping over anything.
• Put the phone in flight mode, if you don't want to be interrupted mid-scan — an interruption is the most costly thing that can happen along the way.

The order to walk the home in

1. Start in the room that matters most. Error in a scan grows with the length of the route, so the first room scanned is usually the most accurate. If the kitchen is being renovated, start in the kitchen.
2. Walk along the walls, not through the middle of the room. You need to be close enough to measure well — a couple of metres, not four.
3. Pause for a couple of seconds in each corner. Corners are the most important points in a floor plan.
4. Keep scanning as you go through a doorway. Walk through slowly and let the camera see the door frame from both sides — the frame is the surface that stitches the two rooms together. If you stop and start over in the next room, the app has no way of knowing how the rooms connect.
5. Walk two laps in furnished rooms — one low along the floor, one raised over shelving and the backs of sofas.
6. Finish where you started, and let the phone see the first corner again. If it recognises a place it has already seen, it can correct its own position.

And throughout: walk at a steady pace. Speed is the most common cause of a poor scan, and the only one that costs nothing at all to remove.

The three things you should bring home anyway

Even a perfectly prepared scan doesn't excuse you from taking a few measurements yourself. Bring a tape measure and write down, while you're there:

• One long control measurement — the home's longest unbroken wall, measured surface to surface above the skirting. That one number tells you whether you can trust the rest.
• Chimney breasts and alcoves — width and depth. These are the details most often lost in a scan, because they're small.
• Openings where something needs to fit exactly — measure the width in three places and use the smallest number.

Example of the control measurement: the tape says 552 cm, the scan says 558 cm. 6 ÷ 552 × 100 = a 1.1% length error, and roughly 2% on areas. Now you know your own uncertainty as a number — and that's worth more than any claimed precision.

Viewing a home and short on time?

Then you can't rearrange furniture and hang up towels. Prioritise in this order: turn on the lights (it's fine to ask), walk slowly, keep scanning as you pass through doors — and avoid pointing straight at mirrors and large windows; pass them at an angle instead. These four things need no permission and remove most of the errors.

What HouseSense does

HouseSense builds the floor plan from the geometry the phone actually measured, and states every measurement as an internal measurement — surface to surface — so you can check each figure with a tape measure yourself. The app never quietly corrects a suspicious-looking room, because then you could no longer tell a genuine error apart from a real detail like an alcove or a bay window.

The principle is that the drawing may be dressed up, the numbers may not. That's why the five minutes of preparation are not a detour — they are the part of the takeoff where you have the most influence over how accurate the result ends up being. And if you have a room that simply can't be made ready — a fixed mirror wall, a fully packed storage room — you can draw that one room on screen with your own tape-measure figures instead.