Today i destroyed a granary, a market and two houses to get 4 tiles available for the slum, normaly i should have lost 100 city population bonus with the destruction of the two houses and gain 200 with the slum, so normaly i should have raise my city population bonus by 100 but nothing happens i just lost the benefit of my two houses.

I start a new game and build three huts (city population limit raise by 3x30=90) i destoyed two of them and loose 60 of my pop cap, then i rebuilt the two huts exactly at the same place has before, but i didn't get the bonus of these two new huts.

Same thing happen with the study, i lost the research bonus when i destroyed it and didn't got it back when i rebuilt the study.

I didn't test with the other buildings yet.