Hi pau 13z,
It's a colorbond steel 2m x 2m shed on a cement slab just above the ground, on a rental property so I don't think they'll take too kindly to me carving a channel into the slab. The slab protrudes about 10 cm beyond each side and I think that is at least partly the cause. Rain falls on the exposed slab ledges and seeps under the steel sides. Problem is the interior gets very humid from the trapped water on the floor which has nowhere to evaporate outside the shed. When you go in on a sunny day after a downpour, there is trapped condensation all over the underside of the roof. I hate it and I'm afraid of my tools getting rusty because of the hot wet air inside. I'm out of room in the garage which is nice and dry.
