is there a modifier to slightly shrink/grow mesh so it doesn't overlap? I have build a building model in Blender.
You can see through it (semi-transparent) to view the floors of the building.

Those floors are simple planes that have a boolean modifier on it.
The object used as boolean is another instance of the house, so the 'cuts' of the floors are done dynamically. 

But then the floors are overlapping with the mesh of the (first) mesh house and it creates artifacts.

Is there a way to add a modifier or something else dynamically that I would enable on the boolean object (house) so that the mesh is a slightly smaller/bigger than the original house mesh so it does not overlap ?

Thanks !
Well, what I always do is select the model, tap the S key, or whatever you may have for scale, and then type in (actual numbers) on how much bigger you want to scale it.
I think it works best when you go to the Object Properties by hitting N and finding the model's scale, then choose either to scale it in the X, Y or Z axis. If all axis' are the same size, just click the highest box and drag down to select them all, find the number and increase it by 0.5 or if you wanna be really precise 0.05, just keep adding to it until you get the desired result.