when does it happen?

[Shinnie02 17]

ok. my region has a total population is around 900,000 my main city has a population of 780,000. The commercial region is filled with wren insurances and stuff. my city is also 80 sim years old. demands for CO$$$ has been at top for about 20 sim years now and my small commercial buildings wont change into larger ones. i checked my desirability for CO$$$ and everywhere was green, i checked land value and it was all high so why wont my small buildings change? theres enough land to.

[wgb24 20]

have you checked your police and fire coverage water power supply and size of zones.

because you might have to resize your zones and make sure there is public transport to those aeras.

[GaBoR 7]

what size are your comercial zoning? 4x4?, Here`s a great thread about getting skycrapers, it has a very useful reply by Peorth who always has an exact opinion about zoning:

https://www.simtropolis.com/forum/messageview.cfm?catid=22&threadid=76600&enterthread=y

[Shinnie02 17]

thanks guys

[Peorth 17]

Maybe you can try the bulldoze method.

The basic idea behind this trick is that your commercial jobs are spread throughout many small buildings. When you bulldoze a couple of them, the simulator will react by rebuilding new C buildings (to keep your sims employed). Sometimes, it will consolidate those jobs into a single bigger new building, which might be the elusive one you're looking for.

Needless to say, always save your city before attempting this. After all, you might have to retry several times before you see the results you want.