In a word? Massively. If you hire someone without experience, they can leave you with a nightmare of a job. Home extensions are infamous for running into snags and having problems; if an inexperienced builder finds themselves unable to fix the issue, it could cost you thousands simply to reverse the damage.
Experience is the first and most important element of hiring any extension builder in Sunbury. You should not take any risks and try to cut costs. You might pay more for an extension specialist, but we guarantee that they will be able to do the job to the standard that you expect. This removes any worries about the extension not being built to the level needed.
Remember, your building regulations and your house insurance expect extensions to be built to spec and to the highest standard. For that, you need experience.