An appointed certifier is a licensed architect, engineer, or quantity surveyor who is responsible for lodging a large number of documents with the BCAR (the building control authority). This involves a lot of work, including disclaiming all details and lodging the application as well as a commencement notice, all of which adds to the cost. It is a relatively new concept, and people are only now beginning to comprehend it. It’s something to think about.
You’re basically restricted in terms of scale and can’t build to the side or front of the house. The addition must be less than 40 square metres in size and should not be visible from the street. As a result, you’ll have to confine it to the back of the building. Often, any previous extensions must be factored into the calculations. So, if there’s an existing expansion, you’ll have to factor it into the 40-square-metre calculation.
However, I would advise that you do not consider restriction to be a drawback. Often small is better – it saves money and maximizes your garden space. There are a number of benefits to keeping it small. It’s also advantageous to be able to do so without obtaining planning permission.