When Is A Conservatory Not A Conservatory

When Is A Conservatory Not A Conservatory

The definition of a conservatory is something of a contentious issue. Conservatories were, originally, temporary structures or very roughly built rooms which were added onto houses in order to ‘conserve’ plants over the winter months. They originated in the 16th century when wealthy households wished to grow citrus fruits which had been introduced to them by traders from the Mediterranean.

Today’s conservatories are much more than a roughly constructed greenhouse for plants, and indeed are as much a well-loved and used part of the home as any other room. But what makes a conservatory a conservatory, and when does it become an extension?

Why care if it’s a conservatory or not?

One of the biggest benefits of erecting a conservatory is that it is permitted development. This means you do not need to seek planning permission, nor do building regulations apply. If you take your conservatory design too far, however, you could shift it into the classification of an extension, thereby requiring both planning permission and building regs to apply.

What defines a conservatory?

Up until 2010, the classification of a conservatory was relatively well defined. Planning guidance said that:

  • Not less than three quarters of the roof should be transparent
  • Not less than half of external walls should be transparent
  • Should be separated from the main house by walls and a door
  • Should not use the central heating from the main house

That made it quite easy to define a conservatory, and gave both householders and builders a good guideline to aim for. However, since 2010 and the introduction of the new Part L of building regulations, the rules on the amount of transparency have been withdrawn, which has left the industry scratching its head as to where the line between conservatory and extension actually falls.

In order to remain a permitted development (ergo a conservatory), the building needs to comply with a number of rules. Some of these are listed here, and there is more information on planning permission and permitted development on our website . Local Authority Building Control (LABC) issued a guidance note relating to conservatories which was intended to clear up the confusion. This document stated that:

  • It must be at ground level
  • It must not be more than 30m2
  • It must be thermally separated from the original building
  • It must have its own heating
  • Glazing in critical zones must meet Part N of the building regulations

This would indicate that as long as a conservatory is separated from the main house by walls and doors, and has its own heating system, it should still be permitted development no matter how much glass or polycarbonate is fitted. Does this mean that anyone can throw up any sort of extension as long as it meets those criteria without any problems? Probably not.

The best practice note from LABC stated that although Approved Document L1B 2006 had been superseded, the general rules about the amount of glass or transparent material required still gave a valid basis for deciding if it is a conservatory or an extension. There is no hard and fast rule about how much glass you should have, and there is now the possibility for a solid roof, but if it starts to look more like an extension than a conservatory, you could run into problems.

It seems there is still some variation as to what the application of the current building regulations to conservatories should be between different local authorities. This means that the best advice would be to talk to your local Buildings Control Office or planning department if you are unsure as to whether you are building a conservatory or an extension.

There is lots more information available at the Planning Portal on this topic, and a lively discussion between builders on this forum.

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