Hi Chris,
I've used the expanding foam on the inside of the bottom gutter of the wall sheets - see this image:
http://www.iceinspace.com.au/forum/a...e.php?a=193555
The inside height of the Colourbond channel is higher than the outside height so in theory the water should drain outside before it overflows inside. The point of the foam was mainly to keep ants at bay.
I've sealed the gap between the bottom channel and the floor with exterior flexible silicone sealant:
http://www.selleys.com.au/sealants/s...rick-concrete/
Since completing that the only issue I still have is some moisture tracking up through the slab, despite two layers of impervious plastic underneath. It currently isn't causing grief however I have considered applying some concrete sealant.