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Does a takeoff app work without internet?

The scan itself never needs internet — it happens on the phone. But many apps need a connection to save, process or export, and that is usually discovered in an empty basement with no signal.

What never needs internet

The measurement itself happens inside the phone. LiDAR sends out light pulses and measures the time until they return; the camera and motion sensors keep track of where the phone is. None of it asks anyone anything over the network. The same goes for Apple's built-in Measure app: it works in airplane mode.

So the answer to the narrow question — can the phone measure without internet? — is always yes. The question is what the app does afterwards.

The four places a connection still gets demanded

1. The calculation happens on a server

Some solutions send the scan up to a server, which builds the model and sends it back. That makes it possible to run heavier calculations than a phone can handle, but it also means you're left with an unusable recording until you have a connection — and that a scan of your home leaves the phone.

Here's how you spot it in the product description: if it mentions "cloud processing", "upload", "processing takes a few minutes", or the app requires an account, some of the work is happening somewhere else.

2. Login on launch

An app that requires you to be signed in usually checks your subscription when it opens. Most of them remember the answer for a while, but not forever. It's the classic unpleasant surprise at a viewing: the app wants to check your subscription, and there's no signal in the basement.

3. Maps and location

If the home needs to be placed on a map — to work out sunlight or compass directions, for instance — the map tiles have to be fetched. The GPS position comes from satellites and needs no internet, but the map image itself does. The fix is to place the home on the map while you still have signal, and only drive out afterwards.

4. Export and sharing

If the PDF needs sending, or the drawing needs sharing with a buyer or a contractor, the actual sending naturally needs a connection. But creating the file shouldn't. Check whether the app can write the PDF to the phone while you're standing in the house, so you can send it from the car afterwards.

How to test your app in ten minutes

1. Switch on airplane mode on the phone.
2. Open the app. Do you get in, or does it ask for a login?
3. Scan or draw a room — ideally the one you're standing in.
4. See whether the floor plan and area appear immediately, or whether it says "processing".
5. Try creating a PDF.
6. Switch airplane mode back off and see whether everything is still there.

If the app passes all six steps, you can safely take it into a house with no signal. If it fails at step 2 or 4, plan around it.

Where it typically goes wrong in practice

• Basements and concrete houses. The mobile signal disappears, and there's no wi-fi to borrow.
• Empty homes. A house being sold or renovated has neither a router nor power.
• Holiday-cottage areas. Coverage can be patchy, which is worse than no coverage at all: the app thinks it's online, and waits.
• New builds. Reinforced concrete and foil in the insulation shield mobile signal effectively.
• Abroad. Roaming switched off to avoid the bill — and then the app doesn't work.

How HouseSense does it

HouseSense runs everything on the device. The LiDAR scan, merging the rooms into one building, the floor plan, the areas, the takeoff, the 3D model with sunlight, and the PDF reports are all produced on the phone — there's no server that has to answer, and no account to log into.

Only two things wait for a connection: syncing to your own iCloud, which happens by itself once you're back online, and the map background, if you want to place the home on a map. Place the home on the map while you have signal, and the app will have the north direction and position it needs to work out sunlight — even offline afterwards.

The home can also be drawn with your finger on graph paper instead of being scanned. That's the most offline-proof method there is: it needs no LiDAR, no light and no connection — only a tape measure and a house to measure.

Four things to do before you drive out

1. Open the app at home on wi-fi, so any login is fresh and any updates are downloaded.
2. Place the home on the map in advance if you'll need sunlight, compass directions or an address. The map only has to be fetched once.
3. Pack a tape measure. It's the one measuring method that never fails — and you should double-check one headline measurement per room anyway.
4. Bring a power bank for homes with no power.

Those four minutes at home save the trip back that otherwise costs half a day.

Battery is the other invisible limit

Without internet, people often stop thinking about power, but a scan uses LiDAR, camera and screen at full tilt at the same time. That draws noticeably more than ordinary use. If you need to measure up an entire home in a house with no power sockets, bring a power bank — and scan the most important rooms first, while there's enough charge to do it properly.

The one answer no app gives you

Online or offline, no app can tell you whether a wall is load-bearing. It measures where the wall stands and how thick it looks — not what it's holding up. That question needs a building surveyor or an engineer on site, and no connection in the world changes that.