After a period of time the roof on existing buildings will need to be replaced. In most situations, this work will need Building Regulations approval.
You need Building Regulations Approval to replace roof coverings, even if the roof covering is exactly the same as the original material. Some minor repairs to flat roofs will not require an application for approval.
Where this type of work is carried out, the roof element will also need to be thermally upgraded by the addition of insulation either in the roof void or as an additional layer where the rafters follow the ceiling line.
Some types of tiles and slates are not suitable for shallow roof pitches. They will not be waterproof in all weather conditions.
Part L of the Building Regulations provides comprehensive advice regarding the provision of adequate thermal insulation to all parts of the building envelope.
Planning Portal - Document L
Further Information is available on the Planning Portal and more detailed information is contained within Document A