Diagonal pavings should prevent wild grass growing through

[Fostik]

we need somebody to divide a large patch of land irl in to square quadrants and plant grass in the center and monitor the way is spreads.

It will depend of soil quality, and amount of light, moist - there will be no any random, that was presented in game.
I wish hafen had those logic for grass/biome/trees spreading, but unfortunately this experiment will show nothing related to game.

[MagicManICT]

we need somebody to divide a large patch of land irl in to square quadrants and plant grass in the center and monitor the way is spreads.

Depends on what variety of grass is planted. Some grasses are very invasive and will cross under several meters of paved road to the other side. (Same grasses will also put roots down 10 meters to water the water table.) Others spread on the wind (or birds, animals) via seed... no matter which way you put it, paving to stop grass growth isn't a "realistic" thought. It's convenient for a game, though, and if possible, I say let's consider it and have the easy way in something.