At first glance, converting an outbuilding or barns into a new dwelling may seem easier and more cost effective than a new build, but this is not always the case. Certainly the fact a structure is in place already may help ease the path to achieving planning permission.
Having a barn or outbuilding of such a stable that could be converted to a dwelling is an ideal opportunity. Firstly, you own it, so the cost implications are reduced immediately but the questions that need to be asked are:
Creating a new build is standard, time-honoured process. Developers and builders know what they need to do and when. Designs, layouts, rooms sizes, and building processes are a known quantity.
Conversions, by contrast, will vary widely. For example, it may be simpler to build new, standard foundations than to modify existing. Likewise with wall structure, strength, and insulation.
Converting an existing structure takes away your ability to precisely locate the new dwelling in the optimum place, and tailor the design (location of windows, for example) to minimise issues such as overlooking private spaces and gardens – both for the donor dwelling and neighbours.
Vehicle access is an important issue, and you will need to demonstrate that access on and off the new dwelling is possible without adversely impacting neighbouring properties and local highways.
This is an important question when it comes to planning. An annexe that is termed “incidental to the property” is a habitable space subservient to the main dwelling, providing sleeping, washing, and food preparation, but ultimately the house and annexe are one and the same.
For them to be sold separately to the main dwelling requires specific planning application for change of use, even when separated by an area of garden or driveway.