The bank will provide the loan to a £230m deal to connect properties, being managed by Netomnia, with internet service provided by YouFibre.
Other lenders on the deal are HSBC UK, ING, NIBC, RBC and Standard Chartered
Nearly half of the total roll-out (up to 675,000 premises) is planned for areas considered to be less commercially viable.
“Fast, reliable broadband unlocks connectivity, opportunity and growth for people and communities across the UK,” said UKIB chief executive, John Flint.
“This is particularly essential for those in underserved areas who currently struggle to connect with work colleagues, family and friends – something many of us take for granted.”