Translation:The engineer measures the surface of the building.
No. It's our way of indicating possession for feminine nouns.
So we have the noun clădire (feminine noun, plural: clădiri).
If we want to say of the buliding we say clădirii:
- suprafața clădirii (the surface of the building / the building's surface)
- paznicul clădirii (the guardian of the building / the building's guardian)
- geamul clădirii (the window of the building / the building's window)
If we wany to say of the buildings we say clădirilor.
For a masculine noun, like urs (plural: urși, bear), we would say ursului and for plural urșilor:
- Laba ursului (the paw of the bear / the bear's paw)
- Ucigașul urșilor (the killer of the bears / the bears' killer)
not really... think about the fact that to articulate the feminine noun, you just add the i at the end, like ”clădire”-”clădirei”, but then it becomes a bit more difficult to pronounce (due to the fact that in romanian all vowels are pronounced), so the ”-ei” at the end transforms in ”-ii”, which is easier to say.
Edit: to clarify, the word ”clădirei” is wrong, it does not exist in modern Romanian (but it was used in the past). However, the articled forms in ”-ei” are quite common for nouns ending in ”ă”, and they followed the same logic like above. Ex: carpetă-carpetei (the form carpetăi is hard to pronounce), casă-casei, etc., but lingură-lingurii.