... you need to be careful how much work is required. If too much of the existing building needs to be replaced, then a crucial court judgment has found that such a project would not benefit from "Class-Q" permitted development rights.
"Class-Q" rights allow certain agricultural buildings to be "converted" into residential dwellings, but not if a "re-build" is required. The legislative details of Class-Q rights can be found here. The trouble is the legislation does not fully define the exact difference between a "conversion" and a "re-build".
In the court case mentioned above, lawyers for the developer tried to argue that his client's project was not a re-build, because it did not involve the demolition of the whole existing building. The judge did not agree.
The proposed project would keep the existing building's roof and its 6 steel uprights, but everything else would be new. The judge said there was too much work required for it to count as a conversion. So, even though it didn't include full demolition, it was legally a "re-build". That's why it could not benefit from Class-Q permitted development rights, and so a full planning application would be needed.
This court judgment now forms case-law and so is relevant for all similar projects.
Even if your project can utilise one of the various permitted development rights available, you may need to register this with your local council in the right way.
If you'd like advice on any of these issues, then feel free to drop us a line.