Is it necessary to get planning permission for adding a conservatory to the back of a house, or do you just need building regulations. No other additions or alterations have been made.

I believe it depends on your cities's building codes.

I just asked my neighbor, who is from England, and he thinks you probably do not need a permit but that, to be certain, you ought to ring the local authority Planning Department.

My experience is strictly with municipalities in the United States, BUT: While the obvious answer is to check with the local Planning Department, you should be prepared to answer/address these potential issues before doing so:

(1) Will the conservatory add to the total square footage of the structure? In some zoning districts (the term used in the U.S.) there is a maximum which can't be exceeded without a waiver or variance from some--usually city--governmental body.

(2) Will it make the house closer to a back- or side-yard property line or public utility easement? In many cases houses must be "set back", say, 25' from the rear property line and 8' from the side. If the house was originally built meeting the rear yard setback, any addition which sticks out may encroach into the setback area.

(3) Are there any restrictive covenants that run with the land; or architectural review boards which oversee modifications to houses in your area?

(4) As a general rule, the better (clearer, more detailed) the drawings and plans that you take with you to the Planning Office, the better are your chances of getting approval without interminable return trips.

Good luck!