Best wood for the job

[skybluescooby]

Hi,
I'm in the process of utilising the gap between the gable end of my house and next doors gable end, The gap on my side is just over a meter wide from wall to dividing fence.
I want to use this space as an area for storage and am currently drawing up plans to build a 1mtr wide x 5mtr long lean to shed.
It will consist of three sides with the fence side being unaccessible once erected so with this in mind whats the best wood to use to construct this bearing in mind maintenance and painting is out of the question when done.
I have three options so far, featherboard, Tounge n Groove or shiplap, heavily treated then erected.

Any ideas or preferences of my chosen three ?
Regards

 

[JohnD]

shiplap is neatest and profiled to shed water. T&G seems to rot at the join. They will all warp and cup with exposure.

Have you considered using ply?

 

[skybluescooby]

Not thought of ply yet, could this be used bearing in mind i want to add a window at one end ?
Is Marine ply the best to use ?

 

[JohnD]

Marine ply is very good , rather expensive. Many people would say use WBP and protect it well. The edges, esp. top and bottom, are the ones you need special protection from water. Some kind of hardwood capping would help. If you can fit something like those concrete gravel boards used on fences at the bottom that would be ideal. You can paint them with masonry paint to make them blend in.