Garden bed for drainage / laying concrete

[Mo2]

Hello there. 

I am planning to get rid of the grass and instead lay the concrete on the side area of my house approximately 42 m sq 

1 - Should I leave any gap between concrete and fence or can lay the concrete until the fence base. 

2 - If I leave the gap between fence and concrete of approx 0.1 for a garden bed so the water can sweep there. Is that feasible?