Dear Barry

Dear Barry, I read your article last month giving advice on the rules and regulations around roofspace conversions and it got me thinking - I would like to build a small sunroom extension on to the back of one of my rental properties. The current tenants move out in a couple of months, so I might take the opportunity to freshen and upgrade the place. It's a family-sized property and I've noticed other rental houses in the area with conservatories and sunrooms, so I think it would be a nice addition to this property to help it compete and get those quality long-term tenants I'm after. I've asked around and can't seem to get a definitive answer on whether conservatories and sun rooms are subject to building regulations or not. If you'll excuse the pun - can you shed some light?? Kind Regards, Davina.
Ask Barry Image

Loving your work, Davina - I always like a good (or even a bad) pun on a Friday morning!

Great question - and it's one I can only answer by asking you a few in return:

  • Will it be built at ground level?
  • What proportion of the roof and walls will be translucent?
  • What's the internal floor area of the new structure?
  • Will it be open plan into the existing dwelling or have door access?
  • What kind (if any) heating/cooling system will the new structure have?

Building Control at Belfast City Council define a conservatory thus:

"An attached structure with door access to a building and with at least two thirds of the roof and half of the walls made from translucent material (that is, they let in light)."

If your planned structure has glazed walls and a solid (ie non-translucent) roof, then, my friend, you are building a sun lounge which is classified as an extension to a property and you will need to apply to building control for approval. Some conservatories are exempt (see below) but a sunroom is always subject to building control regulations.

Another cert for needing permission is an open plan conservatory - if your new structure opens straight into a kitchen or another room with no door separating the two, then you will need to apply for building regulations approval. 

There are certain things that would exempt your conservatory from being subject to building regulations. You won't have to apply for approval if:

  • it's built at ground level
  • the internal floor area is less than 30 square metres
  • it's separated from the dwelling by standard external doors
  • there's no heating or cooling system extended into it
  • there's no fixed combustion appliance or fixed cooling appliance stalled in it
  • the glazing meets part V of the regulations (safety standards)

Although some small extensions are exempt from building control, sometimes you'll find you still need to apply for planning permission, and it's less easy to give you an easy tick list of all those ifs ands and buts. Visit or give the Planning Service a buzz on 028 9050 0510. 

They know their stuff and will be happy to help you navigate the system to get your little building standing proud as soon as possible!


Hopefully this has been helpful to you! If you have a question of your own or any property-related issue I can help you with, don't hesitate to get in touch - drop me a line to, give me a buzz 028 9066 3106 or join the conversation over on Facebook, Twitter or Linked In - links in the top right corner of this page.