In most areas of the country – but not all – it is often possible to design a loft conversion that does not require a planning application, as it comes under Permitted Development (PD). There are certain criteria your conversion would need to meet to qualify for this, and these are covered below, but even if your scheme does qualify, you’d be well advised to get this fully confirmed by applying to your local council for a Lawful Development Certificate first.
This will give you a cast-iron written confirmation that what you are planning to do does not require a planning application. Even if you think you are sure, you don’t
