Hi Gidon,
Great looking storage shed - much better than you could buy off the shelf!
Is your timber pressure treated? I may have had a bad experience but I built a deck from Wickes pressure treated timber and assumed it needed no further treatment. Several years down the line the timber has cracked, split and warped. I was told the pressure treatment only stops it from rotting and it still needs some treatment from the elements.
I maybe wrong and often am - perhaps others could comment?