Lawful development ceritificate for a proposed single storey side extension less than half the width of the original house

Lawful development certificate for a proposed replacment of a dilapidated greenhouse, concrete base and area of hard standing with the erection of a lightweight steel storage building to house animal fee/land amintenance equipment. Building to consist a conrete base, open fronted with profiled metal roofing and timber cladding (Yorkshire boarding type) to the gables/rear elevation