Hello!
I have a challenge I need help solving.

I have a house with a guest apartment of about 70 square meters located above a garage. It was not 100% complete when the house was purchased as it lacked a shower and a complete kitchen. The carpenter (a friend) noted that the beams are old and have a longer spacing than what is typically used now, but it’s not a major problem.
The problem - When we planned where the shower would be, he noticed some movement in the floor underneath. I was then told that tiles wouldn't work well as they would crack and require a firm floor without any movement. To eliminate the movement, we need to reinforce two beams in some way.
Option 1 - Add two brand new beams between the current ones. Complicated and expensive, requiring the garage ceiling etc. to be torn down. The current beams are several meters long.
Option 2 - Install 1-2 columns that support from underneath the garage and hold up the beams, eliminating all movement. The downside is that it takes up car space in the garage + Doesn't look very nice.
Option 3 - To take up less space, you can reinforce from below with a structure resembling < . That is, instead of a column going straight down and up, it goes from the ceiling diagonally down to the wall and then down to the floor. (I forgot what it's called)
Option 4 - Maybe something other than tiles can be used? Something that can withstand more movement?
I will try to provide pictures during the day.
Appreciate any tips!
