All articles · 7 min read

What can you actually measure at a 20-minute house viewing?

Prioritise what you can't work out from home afterwards: ceiling height, clear passage widths, the rooms' real shape, window sill height, and where radiators and soil pipes sit. Floor area, build year and energy rating are already in the listing.

The rule: only measure what you can't find later

A viewing typically lasts 15-30 minutes, and you share it with other buyers. The only sensible way to prioritise is to ask: can I find this from the sofa at home tonight? If you can, don't spend the viewing on it.

You can find afterwards: the home's floor area, as listed in the sales material and the public building register, the build year, the energy rating, the plot size, the running costs, the condition report that comes with the sale, what neighbouring properties sold for, what's allowed to be built on the plot, and where the sun sits over the year for that exact address.

You cannot find afterwards: how high the ceiling is, how wide the gap really is between the door frames, whether the living room is out of square, where the window starts above the floor, where the radiator sits, what it smells like, and how much noise comes in from the road. That's what the 20 minutes are for.

Ask the agent before you measure or scan

You're standing in a stranger's home. Tell the agent when you arrive: "Is it all right if I measure a couple of rooms and do a scan with my phone?" Most agents say yes without hesitation — it's a buying signal, not a nuisance. Some sellers have asked that no photos be taken indoors, and a handful of viewings have several buyers in the same room, where you'd just be in the way. Ask first, and follow the answer.

Be discreet regardless of the answer: don't film personal belongings, don't open cupboards and drawers without asking, and don't walk into a room where a child is sleeping. Scanning a room's walls is something different from a tour through a family's possessions — and you should keep that distinction yourself.

The priority list: ten things in order

1. The ceiling height in each room. One figure per room, measured from floor to ceiling. In older houses it varies from room to room, because the floors have been relaid at different times. Ceiling height decides whether your wardrobes and bookcase will fit, and it multiplies straight into the heating bill: 20 m² with a 2.4 m ceiling is 48 m³ of air to heat — at 3.2 m it's 64 m³, a third more.
2. Clear passage width through doors and hallways. Not the door leaf's nominal size, but the gap between the frames when the door is open. That's the figure that decides whether the furniture gets in.
3. The rooms' actual shape. Wall piers, alcoves behind doors, chimney breasts, duct boxing and out-of-square walls. Your brain straightens them out, and the listing's floor plan often does too.
4. The windows' sill height. How high above the floor the window starts. Under 90 cm in the kitchen means a standard worktop runs into the window sill. Under 40 cm in the living room means the back of a sofa blocks the view.
5. Radiators, soil pipes and fuse board. Where they sit, and how much space they take up. A radiator in the middle of the only sofa wall is a layout decision you can't undo without a plumbing bill.
6. The room's orientation. Which way do the living-room windows face? Pull up a compass on your phone and note the direction — then you can work out the sun's path at home, across the whole year.
7. The kitchen worktop's length and the kitchen's clear floor area. Two figures: total metres of worktop, and the gap between the worktop and the opposite cabinet or island. Under 90 cm is tight when two people need to pass each other.
8. The bathroom, in full. It's the most expensive room per square metre to change. Measure width, length, ceiling height and where the drain sits.
9. Storage that isn't shown on the plan. Knee-wall space, cellar rooms, attic, box room. Note rough dimensions and ceiling height — a knee-wall space with 130 cm to the ceiling is storage, not living space.
10. Outside: shade, overlooking and noise. Stand in the garden or on the balcony for two minutes. Where does the neighbouring house sit, where are the trees, where does the noise come from, and how high is the sun right now?

How to use the 20 minutes

A sequence that works when other people are present:

• 0-3 minutes: walk through the whole home without measuring anything. Just walk. You need to build a picture of how the rooms connect, and which two or three rooms decide whether the home is usable. Notice smell and noise now — the senses dull after five minutes.
• 3-13 minutes: capture the geometry. Either with a tape measure and notepad, or with a LiDAR scan, walking calmly along the walls in each room. With the scan, you bring the whole plan home instead of nine figures.
• 13-18 minutes: the five figures a scan doesn't give you. Ceiling height per room (if it isn't captured automatically), sill heights, radiator positions, compass direction, and any knee-wall heights.
• 18-20 minutes: outside, and questions for the agent. Shade, overlooking, parking — and the two or three questions you prepared at home.

The sum that most often saves a viewing

The classic one: will the sofa fit in? Say the sofa is 220 cm long and 90 cm deep, and it has to go in through a front door, a hallway and a living-room door.

An ordinary internal door with an 80 cm wide leaf gives a clear opening of roughly 72-77 cm, once the frame and the open door are accounted for. That's enough for a sofa 90 cm deep, if the sofa can be tipped on its side and pushed through on edge. But the critical manoeuvre is the corner between the hallway and the living room: if the sofa has to turn 90 degrees through the opening, it's the diagonal across the corner that decides. A useful rule of thumb is that the hallway width plus the door's clear width should be at least as large as the sofa's length — and preferably a bit more. Here: 100 + 77 = 177 cm against a sofa of 220 cm. That's going to be difficult — the sofa will probably have to be taken apart, hoisted in through a window, or you'll need a different sofa. If the figures are close, take one more measurement before you order.

That's three measurements — hallway width, the door's clear width and the sofa's length — and they take 40 seconds to take at the viewing. From home, you can't take them at all.

What HouseSense changes about the 20 minutes

The point of scanning the home with the iPhone's LiDAR isn't that it's faster than a tape measure in any one room. The point is that you defer the measuring. You capture the geometry on the spot and measure it afterwards, at home, as many times as you like — including the measurements you didn't know you'd need while you were standing there.

HouseSense turns the scan into a measured floor plan with the area per room, a 3D model with genuine sunlight based on the address's location and north direction, and a takeoff you can send to a tradesperson. You can also draw the home on the app's graph paper with your finger — useful if the agent won't allow scanning, or if your phone doesn't have LiDAR. Everything stays in your own iCloud; there's no account and no server, so your scan of a stranger's home doesn't end up in any database.

Seen three homes in one Saturday? The difference is noticeable: instead of three pages of figures whose context you can't remember, you have three floor plans you can lay side by side on Sunday morning.

Five things there isn't time for — and that don't matter anyway

• Measuring every room with a tape. You won't get through it, and you'll get skewed figures, because you're measuring one spot in a room that isn't rectangular.
• Counting power sockets. Instead note whether there's a socket missing exactly where you need it for a TV or a desk.
• Checking whether a wall is load-bearing. You can't see it or tap it out at a viewing, and no app can determine it either. If a wall needs to come down, that requires a structural engineer or a building surveyor — ask the agent instead whether there are drawings from any past renovations.
• Working out price per square metre in your head. That's homework, and it's better done with both homes in front of you.
• Debating the renovation budget with your partner in the hallway. Take the measurements home, and have that discussion over a floor plan instead of a memory.

The checklist you can read out at the door

1. Ask the agent's permission to measure and scan.
2. Walk through the whole home once without your phone.
3. Capture the geometry: scan or measure the rooms that decide the purchase.
4. Ceiling height per room.
5. Clear passage width at the narrowest points.
6. Sill height in the kitchen and living room.
7. Radiators, soil pipes, fuse board.
8. Compass direction for the living-room and bedroom windows.
9. Knee-wall, cellar and attic heights.
10. Two minutes outside: shade, overlooking, noise.

Ten points, twenty minutes. The rest is homework — and that's exactly where it belongs.