Why do house doors open inwards but public doors open outwards? House doors generally open inwards for security and public doors generally open outwards for safety.
The majority of front doors open inwards for security. The main purpose of a front door is to keep people and things out of your houses. With a door, the hinges need to be on the side of the door that is opening. If the front door opens outwards, then the hinges would need to be outside. That would make it very easy for any thieves to just pop out the hinges and remove your door. The front door is basically just a piece of wood in a frame and the only thing keeping it in place are the hinges on one side and the lock on the other. If you can just take the hinges out, then the lock will do nothing and the door will just come away.
Another reason front doors open inwards is to make them easier to shut and keep closed. If there is someone you don’t want in your house, it is simple to push the door closed against them. If the door opened outwards, they would be able to put themselves between the door and the frame and you wouldn’t be able to pull it shut. It is also easier to brace the door shut because somebody trying to open the door would have to push against whatever load you placed there. If the door opened outwards, you would not be able to brace it shut.
A third reason why the door opens inwards is because of the weather. If the hinges were on the outside, the rain would rust and damage them. The wind could slam the door shut as well, which might shatter doors with glass in them. If the door opens inwards, the worst the wind can do is open the door. Heavy snow or anything piling up against an outwards opening door could also make it impossible to leave the house.
The fourth reason is for safety. If there is a fire in the house and the fire service need to break in, it is much easier to smash through a door that opens inwards than one that opens outwards.
The fifth reason is also for safety, but the safety of other people. Many houses do not have gardens and are built directly onto the street. If their doors opened outwards, there would be the risk of hitting people walking along the street.
So, why do public buildings have doors that open outwards, then? This all comes down to safety as well. If there is a fire or a disaster in a public building, it needs to be easy for all of the people to stream out of the building. When there is a disaster, people are not thinking clearly and the way out of the building has to be as easy as possible. For this reason, all fire doors also open outwards. If the doors opened inwards, people would have to pull on them, then the people following behind might bump into them and close them. Bottlenecks would form and people would get trapped. If a large group of people rushed towards inwards opening doors, the people at the front might not have time to pull them open, and then everybody would be crushed up against the doors. If they open outwards, the force of the people behind would just push the people at the front through.
The weather is also a reason. Doors to public buildings are not usually locked during the daytime and strong winds would constantly blow the doors open if they opened inwards, allowing rain and snow into the building.
The hinge problem that you would get with outwards opening residential door also exists with outwards opening commercial doors. To stop people just lifting the door off its hinges, they come fitted with concealed or protected hinges. They are stronger and safer, but also a lot more expensive. That is why you generally don’t find them outside commercial buildings.
Sweden is one of the only countries in the world where residential doors open outwards. This is said to be for safety, so that people don’t get trapped inside a burning houses. It is also said to be a prevention against heavy snow. There is the chance that the door might get blocked, but people prefer this to the heavy snow blowing the door open. And this is what I learned today.
Sources
https://ayrtonbespoke.com/why-do-entrance-doors-open-inwards
https://www.vividdoors.co.uk/external-doors/should-external-doors-swing-in-or-out
https://home.howstuffworks.com/home-improvement/remodeling/question584.htm
Photo by Julia Barrantes: https://www.pexels.com/photo/penzance-door-17194373/