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Can you make a floor plan without LiDAR?

Yes. LiDAR is a shortcut, not a requirement — a scaled floor plan only needs real measurements and a fixed scale. Here are the four routes without a scanner.

What LiDAR does — and what it doesn't

LiDAR is a rangefinder in the phone that sends out light pulses and measures how long they take to return. It only sits in the Pro models of iPhone and in the iPad Pro. What LiDAR saves you is the takeoff: you don't have to work out yourself that the living room is 4.12 m wide, because the scanner measures it as you walk around.

What LiDAR does not do is decide what a floor plan should contain. A floor plan is a horizontal cut through the home, drawn to a fixed scale, with walls, doors, windows and measurements. All of that can be drawn just as accurately with a tape measure and a pencil — it just takes longer. There are plans from 1930 without a scrap of electronics that are more precise than a quick scan in poor light.

Route 1: tape measure and paper — the method everything else is built on

The classic method is still the most reliable one, if you do it properly. You need a tape measure of at least 5 m or a laser distance meter, a sheet of graph paper or squared paper, a pencil and an hour.

Here's how, room by room:

1. Sketch the room's outline freehand first — no measurements. Just a rectangle with whatever recesses and alcoves are there. The drawing doesn't need to be neat, it needs room for numbers.
2. Measure each wall internally, corner to corner, at floor height, and write the measurement in centimetres. Measure at floor height, not hip height: skirting boards and out-of-plumb walls make a difference.
3. Measure the room's diagonal. This is the step everyone skips, and it's the one that reveals whether the room is square.
4. Measure the wall thickness in a door or window reveal. Typically 10–12 cm for a light partition and 25–40 cm for an exterior wall in an older brick house — but measure it, don't guess it.
5. Measure doors and windows: the width, and the distance from the nearest corner to the edge of the opening. Two figures per opening is enough.

The diagonal calculation: a room measures 4.12 m × 3.05 m. If it's square, the diagonal should be the square root of (4.12² + 3.05²) = the square root of (16.97 + 9.30) = the square root of 26.27 = 5.13 m. If you measure 5.21 m in reality, the room is out of square — and then you need to draw it out of square, or the floor plan won't fit when you later want to place a wardrobe or a staircase.

The area of that room is 4.12 × 3.05 = 12.57 m². Add the rooms together and you have the home's internal floor area. Note that this figure is typically smaller than the home's officially registered area: official areas are almost everywhere measured to the outside of the exterior walls, while you're measuring internally from wall to wall. In a house with 35 cm exterior walls, the walls take up 10–15% of the external area — least in a large house, because the walls follow the perimeter while the area grows faster. The two figures aren't meant to match — they don't measure the same thing.

Route 2: draw the home in an app instead of scanning it

You can skip the paper and draw directly. In HouseSense the home is drawn on a digital sheet of graph paper: you drag a rectangle with your finger, and that's a room. Afterwards you type in the measurements you took, in whole centimetres — and the drawing adjusts to the numbers, not the other way round. That's the right order: your finger decides the shape, the tape measure decides the size.

Two things make a drawn plan into real square metres rather than a loose sketch:

• Internal measurements are the only truth. Every measurement is calculated wall to wall, exactly as you'd measure it yourself with a tape. So you can always check a figure by going out and measuring it.
• Walls snap together. Drag one room up against another and the two walls become one shared wall. This prevents the classic mistake where two neighbouring rooms both count the same 8 cm of wall, so the home grows on its own.

From there, there's no difference between a drawn and a scanned home in HouseSense: you get a floor plan, floor areas, storeys, a 3D model, takeoffs for contractor quotes and reports you can pass on. And it works on any iPhone and iPad — including the ones without LiDAR.

Route 3: digitise a floor plan you already have

If you have a plan from the sales listing or from the authorities' building-case archive, you don't need to measure the whole house again. You just need to get the scale right:

1. Find one measurement on the plan that you can check in reality — a door width, the length of an exterior wall, a living room corner to corner.
2. Measure it in reality with a tape.
3. If the plan's figure and the real-world figure match, the plan is to scale and you can read off the rest of the measurements. If they don't match, every measurement on the plan needs to be multiplied by the ratio between them.

The warning: floor plans in sales listings are very often not to scale. They're drawn to give an impression, and the small print often says "not to scale" or "indicative". Use them as a reference for which rooms exist and where they sit — not as a source of square metres. Get the real measurements with a tape or from the building case's own drawings.

Route 4: camera apps without LiDAR

There are apps that try to measure rooms with an ordinary camera by comparing pictures taken from several angles. It works — but it works best where there's a lot to look at: patterns, furniture, edges, good light. On a smooth white wall in a dim room the camera has no reference points, and the numbers start to drift.

If you use an app like that, always do this: measure at least one wall in each room with a tape measure and hold it up against the app's figure. If they match, you can trust the rest of that room. If they don't, you'll know before you order flooring for the whole house.

What makes a floor plan "to scale"?

A floor plan is to scale when you can take a measurement from the drawing and find the same thing in reality. That requires four things, and none of them is called LiDAR:

• One fixed scale for the whole drawing — typically 1:50 for a single storey or 1:100 for a whole house. 1:50 means that 1 cm on paper is 50 cm in reality.
• One zero point. Always measure from the same corner in a room. Chain measurements together — "and then another 80 cm, and then another 60 cm" — and small errors add up to a large error at the far end of the wall.
• Wall thicknesses. Without them the drawing can't show how much space the walls eat up, and then furniture and staircases won't fit.
• The measurements written on. A drawing without numbers is a sketch. Write in the key measurements, even if the drawing is to scale.

And one thing a floor plan can never decide on its own: whether a wall is load-bearing. Neither a scan, an app nor a drawing can see that. If a wall needs to come down, a building surveyor or an engineer has to be involved — however neat the floor plan is.

When is LiDAR still the best route?

LiDAR is strongest when you have little time and don't know the home. House hunting, you might have five minutes in a house you've never seen before: that's where the scanner measures what's actually there — including the out-of-plumb walls, alcoves, chimney breasts and bay windows you wouldn't have spotted yourself.

If instead you're sitting at home in your own place with a tape measure and an old drawing, the drawing method is often faster. You already know where the rooms are; you're only missing the numbers.

Getting started without a scanner

1. Walk round and sketch each room freehand — one page per storey.
2. Measure each room's two sides, the diagonal, the wall thicknesses and the position of the openings. Write in centimetres.
3. Draw it to scale — on graph paper or in an app like HouseSense, where the measurements are typed in as numbers.
4. Finally, check one measurement per storey with the tape. If it matches, the rest usually holds too.