Usually not. Since May 2025 the rules in England are more generous than most sources still claim: the old one-metre-from-the-boundary rule has gone, the size limit rose to 1.5 cubic metres, and a detached house can have two units. What replaced it is a noise test — an MCS 020(a) sound calculation showing 37 dB or less at your neighbour's windows, which is stricter than the old limit and is now the only accepted route. We run that calculation at survey and give you the result in writing. Conservation areas, listed buildings, national parks and most central London boroughs are the exceptions, and we check yours before quoting. Scotland, Wales and Northern Ireland have their own rules.