Full Plans or Building Notice?
There are two routes to obtain Building Regulations approval; 'Full Plans' and 'Building Notice'.
Luke Williamson Architect would always suggest obtaining a 'Full Plans' Building Regulations approval prior to starting work on site. This route allows your builder to work from pre-approved drawings and construction notes.
A building notice relies on your builder knowing and building in accordance with the current regulations without any approved drawings to work from. There is therefore a risk that some building work not would have be re-done to comply.
Further guidance can be found here: Planning Portal: Building Control .