External Build Changes Regulations
Although planning permission will be required for most extensions, building regulation approval is almost certainly required too. As long as what you are doing conforms to the government's definition of 'building work' then it will be required, and extensions are the first in the list on their Planning Portal website.
Planning Permission and Building RegulationsThe difference between building regulations and planning permission is that the regulations are about the way that buildings are constructed, whereas planning permission is more about the sort of building that is put up. The regulations ensure that whatever is built is constructed to the correct standards so that it is safe, energy efficient, accessible, soundproof and so on. Planning permission ensures that what is built will fit in with the area in the way it looks and what kind of building it is.
Building regulations separate out into many different areas depending on the type of work that's being done. In order to obtain approval you can go and see the Inspectors at the beginning of the project or seek approval as the work is being done and when it's completed. More details of the approval process itself are on our separate article in this section.
External WallsThe walls of the extension (conservatories have separate rules) should be cavity walls and the effectiveness of the insulation is now controlled by building regulations that have been strengthened to encourage more energy efficient building in the UK. There are also stringent rules concerning the depth and type of foundations that must be put in place.
Changes to the walls where the extension meets the house will need approval too, as they are classed as external walls until the work is completed, which have separate rules to those for internal walls. Often an opening will be made, or an existing window or door opening significantly enlarged, to allow access into the new part of the home, and it's critical that any lost strength is replaced when this is done.
Roofs and Loft ConversionsRoofing is also covered by a number of building regulations, depending on the work that is being carried out. If your extension is a loft conversion then there may well be some building regulations approval required for changes to the roof, but also many other aspects of the build.
You will need to make sure that the strength of the ceiling is not compromised. Access to the loft will be subject to stringent scrutiny, in particular the pitch of the stairs and the fire safety angles. It could be that you will have to make provisions for a separate fire exit, perhaps from a window, and there must be adequate sound insulation between the loft and the rooms below it.
Assuming you aren't doing a loft conversion but perhaps extending the roof to cover the new extension, then that will probably be considered a structural alteration and building regulation approval will be required. It is likely that work of this kind will affect the original roof structure too, particularly where the new part joins the old, but as long as less than 25 percent of the roof area is replaced, and the covering material weighs no more than 15 per cent of the original material, then approval is not required.