Simply putting down rock will not stop vegetation growth.
To attempt to eliminate all vegitation growth you need to:
- Remove the sod and top soil
- Spray the area with pre-emergent vegitation stopper to stop any seeds in the soil from germinating
- Put down a layer of compacted sand to restore the height of the removed top soil minus the thickness of the stone
- Put down heavy duty landscape fabric
- Put down the washed stone.
Even after all this you will probably have to spray certain spots with vegetation killer a couple times per year.
Grass, in all its varieties, is the single most successful plant on land. It will not be stopped easily or for long.