Conservatories
When considering a conservatory you need to apply for planning permission:
If your property is a flat or maisonette (including those converted from houses) or a commercial property, such as a shop or public house.
If the conservatory, or any part of it when built, would be nearer to a highway than the nearest part of the original house unless there is at least 20 metres between the conservatory and the highway.
If the property is a listed building.
If more than 50 per cent of the garden excluding the area of the original house would be covered by extensions (including the conservatory) or other buildings.
If the conservatory is higher than the highest part of the roof of the original house.
If any part of the conservatory is more than four metres high where it is within two metres of the boundary of your property.
If for a terrace house (including an end-of-terrace) - or any house in a Conservation Area, a National Park, an Area of Outstanding Natural Beauty or the Broads � the volume of the original house would be increased by more than 10 per cent or 50 cubic metres (whichever is the greater).
If for any other kind of house outside those areas, the volume of the original house would be increased by more than 15 per cent or 70 cubic metres (whichever is greater).
If, in any case, the volume of the original house would be increased by more than 115 cubic metres.
and also building regs
Conservatories are normally exempt from building regulations when:
They are built at ground level and are less than 30 square metres in floor area
At least half of the new wall and three quarters of the roof is either glazed or translucent material
The conservatory is separated from the house by external quality door(s).
Glazing and any fixed electrical installations comply with the applicable building regulations requirements