Hi all,   I'm new to the forum but already found some useful guidance on here, so thanks. I'm also new to this level of DIY but I'm not shy at having a go, like to make sure things are done correctly (hence my questions) and have a brother who's handy at a lot of things to help (who's also a spark :))   So let me set the scene first. The garden room I want to build will be 5m x 3m to stay within the 15m2 limit and needs to be close to the perimeter so I'm limited to