If, however, your garden building does comply with the above criteria, you won't need to apply for planning permission and you can have a garden building up to 30m2 (internal size). anything bigger than 30m2 will need to go through building regulations.. Whilst they typically wont require planning permission before construction can get underway, there are certain limits and conditions that need to be considered when looking for a garden shed permission: garden sheds and outbuildings must be one story, and eave heights cannot exceed 2.5 metres.. Planning permission sheds lean to shed plans for free bike shed plans free 12 x 20 awning how to make a horse shed loft.shed.plans.14x16 free back yard shed plans will enable you to discover about planning and constructing different garden sheds..