I have a mammoth task in front of me. My garden is in 3 tiers with 2 very large raised beds.these beds are now covered in pebble and soil. I have shifted a lot of the pebbles off already but it looks like I've not even touched it. I'm now thinking to keep cost down to put Bark over the area's for a play area. What would be best yo install this? Would it be sharp sand, membrane than bark? I have pictures to help. I will also be fitting patio slabs on the middle deck.