Jarmstrong

Hi, I am in Essex and I would like to build an outbuilding 4.9m x 2.7 meters (approx 13sqm) and 2.8m talk near the neighbour boundary. I would need planning permission because it is above the 2.5m tall permitted development limit. Would I need building regulations approval as well? According to planning portal, an outbuilding less than 15sqm would not need building regs approval. Have I understood the rules correctly that I can apply for planning permission, but need not get building regulations approval for this outbuilding? Thank you for any advice or guidance.