Can an app tell which way a door opens?
No. Neither a LiDAR scan nor a camera can tell whether a door is left- or right-hinged, or whether it opens in or out. That is something you choose yourself — and there is a good reason it cannot be guessed reliably.
Short answer: no, a scan cannot see which way a door swings. A LiDAR sensor or a camera registers that there is a hole in the wall and how wide it is — but a door leaf sitting closed in its frame looks the same whichever way it opens. The hinge side and the in/out direction are therefore always a choice the user has to make, not something a drawing app can work out on its own. Most apps solve it by letting you pick between the four possible combinations when you edit a door.
Why can't the sensor just see it?
A door sitting closed in its frame during a scan fills exactly the same hole in the wall regardless of whether it's left- or right-hinged, and regardless of whether it opens into the room you're standing in or into the room on the other side. The sensor sees an opening with a width and a height — it doesn't see the hinges, since they sit hidden in the frame, and it doesn't see which way the door leaf is meant to swing, because that requires someone to actually open it while the scan is running.
Even if the scanner did catch a door standing open, it would still have to work backwards from the leaf's angle to which side the hinges are on — and that information is often simply not present in the geometry an ordinary room scan collects.
The four options you choose between
A door has two independent choices that together give four combinations:
- Hinge side: left or right, seen from the side you normally enter from.
- Direction: into the room or out of the room.
Left+in, left+out, right+in, right+out — those are the four states, and they're all equally likely until you've actually seen the door and know which one it is.
Why does it matter at all?
The door's swing claims a quarter-circle of floor area, and that area can't be occupied by furniture if the door is to open fully. If the drawing points the wrong way relative to reality, you risk planning a bed or a wardrobe exactly where the door leaf actually sweeps — and only discovering it once the furniture is in place. Direction also matters for how people pass through: a door that opens out into a narrow hallway can block it for others, while the same door opened into a large room causes no trouble at all.
How do you pick the right one if you don't remember it by heart?
Stand in front of the door and look at which side the hinges sit on — they're usually visible as three or more metal fittings along one edge of the frame. Then gently push the door, or recall which way it normally swings when used. Most internal doors in an ordinary home open into the smaller of the two rooms they connect, or into whichever room's floor space best absorbs the swing — but that's a rule of thumb, not a rule without exceptions, and the only reliable method is to look.
How do you draw a door swing correctly on a floor plan?
The standard is a quarter-circle arc: a straight line (the door leaf, drawn in its 90-degree open position) and an arc from the leaf's free edge back to the wall, with the same radius as the door's width. The arc sits in the room the door opens into, and one end of the arc — where it meets the wall at 0 degrees — sits on the hinge side. A door with no arc is either an open passage with no leaf, or a sliding door, which is instead drawn with the door panel resting beside the opening.
If you're drawing it by hand yourself, the order is: draw the hole in the wall first, then decide the hinge side and direction, and only then draw the arc with a compass or a fixed template, so the radius matches the door's actual width.
What if you pick the wrong one — does anything serious happen?
No. Choosing the wrong door swing doesn't change any of the measurements the drawing is built on — not the room's area, not the walls' lengths, not the door's width. The only thing that's wrong is the display of which way the leaf swings, and that can be corrected as soon as you spot the error. It's a display detail, not a measurement error, and it can't harm anything else on the drawing.
Is it different for sliding and folding doors?
Yes. A sliding door has no swing to choose — the panel glides along the wall instead of swinging out into the room, and so it doesn't claim a quarter-circle of floor. A folding door concertinas in the middle and typically takes up less floor space than an ordinary door of the same width, but more than a sliding door. Door type is a separate choice from swing direction, and a drawing should show them differently, so a contractor or a furniture layout doesn't allow for a swing that isn't there.
What about a scan that caught the door open?
Even then the information is often unreliable. A scan where the door happened to be standing open at a particular angle could in theory reveal the hinge side — but most room scans aren't built to recognise and interpret a door leaf's position specifically. In practice, virtually every floor-plan app therefore treats door swing as something the user specifies, regardless of whether the door was open or closed during the scan.
What HouseSense does
Every door on a measured or drawn floor plan can be assigned a swing manually: hinge side and in/out, the four combinations. The choice is drawn as an arc on the floor in the 2D plan — the door leaf is never shown as a physical object in the 3D model, because that would require an assumption the app can't stand behind. If you pick the wrong one to start with, you correct it with a single tap, without affecting any of the other measurements.
In short
- No scan can see the hinge side or the direction — it's always your choice.
- The four combinations are left/right × in/out.
- The arc on the drawing sits in the room the door opens into, with its point on the hinge side.
- A wrong choice harms no measurement — it's a display you can correct at any time.