I own a piece of agricultural land that falls shy of 0.4 hectares, therefore I am not able to submit 'prior notification' planning applications to the council for new buildings.

However, I have been informed that I can repair and extend the existing (wooden) buildings. Does anyone know how far I can go with repairs and extensions?

I have one 'shed' of approximately 7ft by 16ft. The roof requires replacement/rebuilding, and the whole structure needs pulling straight, as it had a metal gate propped against it for years and its all warped.
My plan, if possible, is to install 4" x 4" posts along each side of the 'shed', pulling it straight and supporting it as I go, remove the apex roof, and install a new roof on the posts. However, the new roof will be a single sloping roof, rather than an apex, then I was going to slope the roof down the other way to give a covered area next to the original 'shed', to allow for undercover storage of straw and such like.
The length would still be 16ft (for now), but the width of the roof would be 14-16ft; the width of the shed would remain the same.

If I could extend the shed (and 'new' covered area) a further 8-10ft to 24-26ft, that would be of great use. But I don't want to push my luck!