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What should I write down when taking off a home's measurements?

Every wall's internal length, at least one diagonal per room, ceiling height at several points, every door and window with the opening's size and its distance from the nearest corner, wall thickness, and which room lies on the other side of each wall.

The rule: a number without a line is worthless

The most common mistake in a takeoff isn't measuring wrong. It's measuring correctly and then not being able to remember what the number belonged to. "312" on a scrap of paper isn't a measurement — it's a riddle. Was it the wall, the door's distance from the corner, or the ceiling height in a different room?

So the one rule that actually matters when taking measurements is: write every number on the line it describes, on a sketch. The sketch doesn't need to be neat or to scale. It just needs the right number of walls, doors and windows, so every number has somewhere to live.

Per room: the eight items

1. The room's name and floor

"Living room, ground floor", "Bedroom 2, first floor". It sounds redundant while you're standing there, and is impossible to reconstruct a month later when you're looking at five sketches of rectangles. Number the rooms too — 1, 2, 3 — and write the number on the sketch, so you can refer to them without spelling out long names everywhere.

2. The internal length of every wall

Measured along the floor at roughly 10 cm height, wherever the skirting allows. Measure higher up and you'll hit curtains, radiators and window sills. Write the figure in centimetres, and note if you measured around a skirting board or a protrusion.

3. At least one diagonal

Corner to corner, across the room. The diagonal is the measurement that decides whether the room is square, and it's the only one that locks the shape down. Without it, a room with four known walls can still be drawn in an infinite number of shapes. Write it across the sketch as a dashed line, so it isn't mistaken for a wall.

4. Ceiling height at three points

Two opposite corners and one point in the middle of the longest wall. Write down all three figures, not the average. If they differ by more than 2–3 cm, it matters for anything going up to the ceiling.

5. Every door

Four things: the opening's clear width between the insides of the frame, the opening's clear height from floor to the underside of the frame, the distance from the nearest room corner to the edge of the frame, and which way the door swings (in/out, hinges on the right or left as seen from the room). Without the distance from the corner, you know the door's size but not its position — and the room can't be drawn.

6. Every window

Four things again: the opening's width, the opening's height, distance from the nearest corner, and the sill height from finished floor up to the top of the window frame. The sill height is the one people forget, and it decides whether a 90 cm worktop clashes with the window, whether a radiator can sit underneath, and where the light falls in the room.

7. Wall thickness

Measured straight through a door or window opening, since the wall is already cut through there anyway. Without wall thickness the rooms can't be assembled into a floor plan, because two neighbouring rooms need to be pushed apart by exactly that thickness. Measure it in several openings — thickness is rarely consistent in a home with an extension or added insulation.

8. What lies on the other side

Note beside each wall which room, which staircase, or which outdoor space lies behind it. It's the only piece of information that ties the rooms together into a home, and it's impossible to guess afterwards from five separate sketches.

Four recording rules that prevent the costly mistakes

• One unit, all the way through. Pick centimetres and stay there. Mixing metres and centimetres is the most common cause of a factor-of-10 error — "3.5" becomes 3.5 cm instead of 350 cm.
• Write a check measurement. The wall's full length, next to the sum of its parts (corner → window → window → corner). If they don't match within a couple of centimetres, there's a mistake, and you'll find it while you're still standing in the room.
• Write what you measured from. "From the left corner to the outer edge of the frame" — not just 87. The outer edge of a frame and its inner face sit 5–6 cm apart, and that's often enough for a piece of furniture not to fit.
• Date the sheet. Date and address at the top of every page. A takeoff without a date can't be checked against a later renovation.

Worth writing down beyond the measurements

A takeoff becomes twice as useful if you also note the things that can't be measured but that you only notice while standing there:

• Where sockets, TV points and light switches sit — ideally the height too. It affects furniture placement more than people expect.
• Radiators: width, height and distance from the floor. A radiator is the most common reason a cabinet can't stand where it's meant to.
• Floor type and direction of boards or planks. The direction determines how much waste there'll be on a replacement.
• Ceiling type: solid, suspended, plaster, timber. A suspended ceiling means there's space above it — and that height can potentially be won back.
• Damp, cracks, uneven floors. Write down where, not just that. A photo with the same number as the sketch is worth its weight in gold.
• Which way is north, or simply "the windows face the garden, which faces south". It's the starting point for working out daylight later.

From paper to drawing

Measurements need to be drawn up while they're fresh and you still remember what they meant. Go through the sketches room by room and draw them to scale — on graph paper, in a drawing app, or on a phone.

Drawing by hand, start with the longest wall, set the diagonal with a compass or a string, and write the measurements on the drawing rather than beside it. Draw the openings with their own dimensions, so a door or window sits exactly where you measured it — it's the position, not the size, that goes wrong when you draw from memory. If you have an iPhone or iPad with LiDAR, you can scan the rooms in HouseSense instead and use your hand measurements as a check on the figures.

Whatever the tool, the same thing holds: a takeoff is only as good as its notes. Eight items per room, every number on its own line, one unit throughout, and a check measurement that catches the mistake while you can still fix it.