Jz stumple upon this thread

I am supplier in building materials

Theres much we can learn from each other

expensive to build coz u already completed first floor without consider the foundation for 2nd storey. by add 1 more floor, u need a stronger foundation, stronger column and therefore a lot of abortive work need to be done. eg. such as u need to strengthen the column, do the underpinning work to have stronger foundation. perhaps hack off some ground floor slab just to increase few more footing and so on. need to engage consulting engineer to come out the drawing for u also. ain't cheap.

ohh at the backyard. if like that it should be fine. just new foundation to backyard, new ground floor and new upper floor. get a consulting engineer and they will do everything for u. including local authority submission and approval. if u need it then just build it lo

it's not advisable to do it without getting endorsement from engineer and approval from local authority. even u can over design it to ensure it's perfectly secure, sometimes unforeseen thing will just happen. if something happen and even not due to ur fault, not due to ur structural design issue, they will still pin point at u as u didn't get endorsement for the work and no approval from local authority at first place. so u lose the case b4 even it require to assess ur secured design.

anyway it ain't expensive also la. all those material is cheap. maybe u estimate about RM125/sqft for ur work. normal finishes, not expensive type. but endorsement and local authority expenses would be a lot as ur quantity is small yet the same procedure had to be go through.

construction industry so broad. variety of profession. what u want? the only party who earn big buck is developer.