Garden shed is modern, galv, about 3m x 2m. Sits on concrete slabs that slope for runoff. Has a maybe 75x75 internal wood frame. Sits on geez, that black water separation thing that starts with M. Ill remember later, it comes on a roll. Bolted down with 2 bolts and a right angle. Cool shed.

But the black water separation stuff that I cannot recall the trade name of, is supposed to stop water seepage, it doesnt, by a long shot.

I need to look at ways to watertight the edges. So its not swimming inside.

Ideas:

1. Put sealer goop around the edge, but the gap between the concrete and galv is not much over 5mm, so hard to goop it and finger it smooth

2. Raise it 75mm and lay 75mm treated strips onto concrete and attach a timber strip floor, and just let the water run under. Concerned over warping the galv

as I crowbar the base. Maybe its quite light to crowbar and with the wood frame which is in the base as well be ok? Need to buy or get made another set of right angle for the bolts as it wouldn't then reach the bolts.

3. Raise it a smaller amount, say 5mm and pack it, to allow water run through, and make a free standing joist/plank floor. 

4. Raise it a small amount, say 10mm, put a 10mm treated wood foundation around the perimeter, that will allow the bolts to reach. Paint and seal that.

Malthoid, thats it

Whaddya reckon? Any other options or gotchas?