Yes, slate is an expensive material to purchase, time-consuming and expensive to install, but a slate roof will last for a century and more with proper maintenance. Considering the long-term value of slate, it is probably the least expensive choice for your roof. An asphalt roof will need to be replaced every ten to twenty years, but your slate roof will only require minimal maintenance every twenty years or so.
This tall shed was made from posts and rafters recycled from an old pheasant coop. The roof is Galvalume. We sided it south-facing so that we can put solar panels on it. The siding is pine shiplap. The shed was constructed to be able to move easily. The bottom plate is made of 6×6 skids, sitting on a 10 inch gravel base.
The dimensions are 12 x 20′ and 15′ high at the peak.
Here it is show before the door is installed.