Civil. Structural engineer -- 2

I am thinking of redesigning my house, are you able to analyse the structure and advice me how it’s possible to rebuild

Engineering design

I have a 3 storey bungalow with which has a tiled (heavy) pitch-roof attic which low ceiling and a big backyard which has sewer and drainage lines going underneath.

I would prefer minimum changes to the house foundation and structural aspects, and request you for an analysis and report on the current structure’s ability to handle the variations in load, and advice how to mitigate

1. Load reduction from tile roof to metal roof
2. Load added on level 3 to make the shape nearly rectangular floor plate and a mezzanine at the Center as indicated in my drawing with yellow
3. Load added on L2 with backyard and bedroom extensions

L3 works

I would like the old roof replaced with a modern lightweight metal roof that is raised by 5m from the third floor, so I will get a rectangular plate on level 3 with spacious ceiling.

In addition I would also like to add a mezzanine at the third floor since it is very high ceiling.

All these rc floor slabs will add weight and I’d like your calculations to assess the feasibility of this, and advise on possible load transfers etc if required.

In level 3, the following areas which have new rc floor slabs

Near the lift, where the plants are shown about 5ft x 5ft (currently it’s void)

Bath room area which is above the pool about 10 ft x 10 ft (currently it’s void)

Movie area about 10ft x 10ft (currently there is a service rc floor there but not full load bearing floor)

L1 (ground floor) works

The ground floor has a backyard which has sewer and drainage lines underneath.

Is it possible for me to extend the building by 3 meters to the rear as per architects diagram. Extension is for L1 and L2 including a lightweight roof.