In 2013 the Department for Communities and Local Government issued a directive regarding conservatories and porches and whether they must comply with Building Regulations or whether they are exempt.
The guidance applies to England and Wales and qualifies when a conservatory or porch is built at ground level and covers an area of not more than 30m², in probability it will be deemed exempt subject to satisfying all of the following accompanying conditions:
The decision of whether or not a conservatory or porch extension is exempt is a matter for Building Control bodies on a case for case basis, taking into account the above conditions and the amount of glazing that makes up the new walls and roof.
Construction is not exempt if it fails to satisfy all the above requirements. The Department for Communities and Local Government qualifies that should a relevant Building Control body decide an extension is no longer an exempt conservatory or porch, Building Regulations will apply.
Building Regulations require certain parts of a structure to be dry and free from damp. Therefore, an extension or a porch attaching to an existing cavity wall will require measures at the roof/wall intersection. An external flashing and wall cavitrays will arrest permeating dampness from gravitating downwardly below the new roofline and provide a speedy solution to satisfy / regularise this particular construction requirement. Type E and Type X Cavitrays for flat and sloping roof abutments are manufactured by Cavity Trays Ltd of Yeovil.