Lean to Greenhouse leaking water

I have constructed a 6 x 4 lean to polycarbonate against the wall (of course) but as the wall is uneven I fastened it against wooden battening. The only problem is the rain sits on the battening adjacent to the roof and seeps down through the crack. I would have thought after sealing with silicone sealant this would have stopped the water. Not the case 

Ant tips on how to stop this. Obviously I will have to put something over the wood to divert the water down the sloping roof.