Whenever you make a structural improvement to your home, whether it's large or small, check first with your local authority. You may need to apply for planning permission and/or comply with building regulations. An architect or consultant working on your behalf should do this automatically. The rules and regulations can be complicated, but they have the force of law - they exist to provide a pleasant and safe environment for everyone. It's worth being on good terms with the staff of planning and building control offices, who are there to help.