The answer to this is 'depends'. As Miss Zippy says, most houses are allowed 70 cubic metres to be added on, which is ample for a conservatory.However, we built one last year, so thought we would contact our local council. Their rules are that this 70 m^3 is OK, as long as the double garage (if you have one) is attached to the house. If it is detached, that is your 70 m^3. As our garage is detached, we needed planning permission (even though it is only 1m away!!). Our neighbours, whose garage is integrated, would not. Even another neighbour, who has a little brick arch over their back gate (the passage being between the garage and house) don't need it as the house is connected to the garage by the brick arch. Phone your local council planning office and ask them. It is the only way to be sure. Also, if you have a newish house (say less than 10 years) check your deeds for any covenants regarding conservatories. We had to pay �100 to the developer to get permission to build the conservatory. Whilst you might ignore this, it will come back to haunt you when you come to sell your house, as the solicitors will find a discrepency in the deeds and make lots of money out of you. Last point, do it. It is wonderful to sit out in and watch the birds in the garden or whatever. We built most of ours ourselves, so cut the cost in half as well.