How to edit the tiles of a floor?

[Toph3]

the urban pavementthe component characteristics

Hello, 
I am designing an urban pavement, I have already definied the pavement and its layers and I have definied a pattern for representing the tiles. However, now I would like to represent the real Position and and Change in Dimension for those tiles which are near the external border of this urban pavement, in the proximity of the public road. In other words, I want to design different „types“ of tiles (for example the one near a curve would be curvy and bigger than the one in the center, with a normal rectangular shape, for resistance motives); but by only applying the pattern obviously there will be some parts of the urban pavements with an irrealistic positioning and dimension of the tiles.
I wonder how can I obtain this level of details? Is it possible through the materials characteristic? Or should I directly solve this matter by modelling exactly the elements I intend to represent?
I will attach two Images of the urban pavement near the curve whci I would like to edit and customize. 

Thanks in advance for the help, 

Kind regards
F

[barthbradley]

I would suggest a BIM approach.  Separately model the geometries which represents the different materials/applications.   Additionally, you can use the Split Face tool (Modify Tab). 

https://knowledge.autodesk.com/support/revit-products/learn-explore/caas/CloudHelp/cloudhelp/2018/EN...

...just to confirm: the gray element in your screenshot is the"Urban Pavement"; Right?  May I ask what method you used to create it?  

[Toph3]

Hello Bradley, 
thank you for your suggestion and also for the quick answer. I am quite new to Revit, I have taken a basic course some months ago but only now I am really using the software so I feel I have to do some revise and to relearn some processes. Thus, sorry if I might ask some silly question now, but to put it simply you were suggesting to model the precise tiles (of different sizes) which I need and then to use the split command to apply them in those part/surfaces of my sidewalk where I need to put these different sized tiles? Is it correct?

Regarding your question, the grey pavement is actually the traffic road, whereas the pavement with the pattern on it, in a more yellowish color, is my "urban pavement" for pedestrian use (the sidewalk), both the areas were modelled beforehand by my friend and I think she used a normal floor command.