Under Holborn streets the diggable stock is narrower than the postcode suggests: townhouses and converted professional buildings on the Camden–City edge. We filter out leasehold flats first, then test whether a freehold house truly needs below-ground space rather than a rear or loft enlargement toward Bloomsbury.
The planning frame for Holborn is Camden / City of London: authority confirmation is mandatory before drawings. We scope evidence to that authority’s lists and refuse generic “London basement policy” numbers that do not apply to this pin.
Title is the first Holborn drawing. If the client is a lessee under a freeholder who retains structure and subsoil, we stop the basement brief and redirect to works they can actually consent. Only clear freehold control proceeds to investigation.
We commission plot-specific ground investigation for Holborn basements: foundation depths, groundwater and obstructions decide the retaining method and whether under-garden elements survive, long before application drawings are fixed.
Because pavement vaults and tight courts, Holborn basements notify early and often. We map every notifiable owner before a programme date is offered, including internal parties in converted houses.
For Holborn basements, we treat water as a primary design driver: dual-system waterproofing to BS 8102, twin pumps, backflow protection and ventilation planned with the tanking so the box does not become a sealed cellar.
On Holborn plots the lightwell package — retaining walls, guarding, steps, grilles — is designed first. Short gardens toward Covent Garden and tree constraints can veto a habitable dig even when the structure is sound.
Holborn clients often arrive asking for a basement when Licence to Alter and freeholder rules dominate. We price both routes so the dig is a choice, not a default.
Distinctive to Holborn: townhouses and converted professional buildings on the Camden–City edge combined with pavement vaults and tight courts. That pairing changes bay sequences, spoil routing and which households must be served notices before excavation.
How authority confirmation is mandatory before drawings meets the site compound in Holborn: if the lightwell eats a short garden or trees block the only access, the floor plate shrinks until external works are buildable toward Bloomsbury.
Do not copy a dig from Bloomsbury or Covent Garden into Holborn by postcode similarity — Camden / City of London evidence thresholds and local grain differ street by street.
Construction hours and vehicle routing on Holborn streets are written into the package early, because neighbour awards and Camden / City of London construction-management expectations often gate the start on site more than the decision notice does.
Delivery in Holborn runs investigation and structure before Camden / City of London submission, then awards and building regulations; we set that longer programme at the first meeting so the dig is planned as a project, not an add-on. Spoil logistics and temporary works are written into the package rather than discovered at tender.
