Lining/ Draining a wooden raised planter ???

[shambolic138]

I'm looking to build a raised planter reasonable similar to the example here.

Beds will not be massive (just to fill a gap in hedge/cover fence):
- Bottom bed: 8" high x 16" deep x 3ft wide, (this will be 22" off floor)
- Top bed 8"x8"x3ft

I will use treated timber, but wondered if anyone could give advice on lining, and draining?

I guess use some plastic sheeting to protect the sides and base with 2x1" drainage holes and some stones below soil? Use Tar paint round the drain holes?

Thanks for any thoughts - cheers

 

[freddiemercurystwin]

You're overthinking it, use some bubble wrap to line them held with some drawing pins, but why would you use gravel if you're gonna put holes in the bottom?