The amount is up 20% from the £12.8bn mortgage funding seen this year and is almost twice the £7.8bn provided by the bank in 2007.
HSBC is hoping the funding boost will see its market share go from the current 4% to 5%.
The bank has also pledged to make another £1bn available to small business customers in the UK.
Paul Thurston, managing director of HSBC UK, says: “By some estimates net mortgage lending in the UK will fall next year.
“But HSBC has no intention of closing its doors to customers, nor will we compromise our reputation for responsible lending. We remain open for business to the tune of £15bn.”