A friend's renovation actually added a whole extra level inside the home, and the property management had no idea, sparking heated discussion in the neighborhood

When it comes to houses, what everyone cares about most is the price and the renovation. I have a friend who used to work in design, so when his family bought a house, he did the renovation and design himself. But the house was only just over 90 square meters, and he actually "floated" an extra level inside it. It caused a huge uproar in the neighborhood group chat, and the funniest part was that the property management had no idea. But when I went to his place to see it, I really was blown away.
His house was converted from a single-story flat into a small duplex layout, and it was very beautiful. You could not tell at all that it was a flat of just over 90 square meters; it looked like a small villa. He told me that when he bought the house, he specifically chose the top floor, because the top floor has one advantage: the ceiling height is greater than that of the other floors. He said, my ceiling height is nearly more than 4 meters, so it is very suitable for designing into a small two-story duplex.
Looking at the frame in their home, I asked what it was for. He said this frame is used for load-bearing, so when I bought materials I chose the sturdiest construction materials, because for safety the load-bearing frame definitely has to be a good one, otherwise what if it collapses after you move in?
I asked him, will the property management agree to you doing this? He said, when I started work, I did not communicate with the property management at all and just started construction directly. When I was almost finished, I sent the pictures to the neighborhood group chat, and the neighborhood instantly started a heated discussion. Some people said this was not good, that this was not allowed and so on, and some owners praised me, saying my home was decorated quite nicely and looked relatively spacious, and they wanted to do it this way too. Because everyone was discussing my renovation so much, the property management came over to take a look once. He said fortunately I understand design, so there was no violation, and everything met the requirements, which was what saved me from the risk of forced demolition. After the installation was finished, the property management asked me to go and handle the procedures that had not been done before.
Seeing his finished house, it looked quite nice, but I still think that before renovating, everyone should communicate clearly with the property management. If you fail to meet the property management's requirements, the property management will make you stop work or directly demolish it. Fortunately my friend's home did not violate any rules, otherwise the loss would have been huge.