Weed barrier with stones

I'm planning on putting some stones (pebbles) in the garden, is it best to still put weed barrier down? And how deep a layer of stones is best?

Yes, and 3-4" is ideal

TT

Can have my fecking stones hate them!!

I'm planning on slabbing my front drive. She wants tarmac. Whats the best way? I want drainage, so slabs would be best in my opinion. Will the weed barrier be ok?
Also, whats best, spotting cement, or making sure its flat first and a quick layer of sand?