How do i convince my dad to turn his shed into a workshop?

hey, I am a 12 year old boy who loves woodworking and i have heaps of tools, i have been wanting to save up for my own shed but they are too damn expensive... and we already have a shed but it is full of crap that half of it we don't even need anymore, if he said yes i would clean it for him and stuff, even if i only got half of the shed it would still be enough. how do i convince him, he is a tough cookie to crack too... thanks