Building societies lent £68.9bn in 2018, an increase of 7 per cent from 2017, which saw £64.1bn loaned, according to BSA.
BSA adds that 476,803 new mortgages were approved in 2018, increasing 7 per cent year-on-year, with an estimated one in three being first-time buyers.
Meanwhile, net lending totalled £17.9bn last year, having increased from £16bn the year prior.
Of all outstanding mortgage balances, 23 per cent were held by building societies last year, equating for £322.3bn, up from £298.7bn in 2017.
BSA chief executive Robin Fieth comments: “Building societies performed strongly in Q4 2018, adding to a robust performance for the year as a whole which was delivered despite challenging market conditions.
“The housing market was and remains subdued, with little growth except in remortgages.
“Here homeowners have been locking into deals while interest rates stay low, to provide some financial stability in uncertain times.
“Mortgage product innovation remains a strength for the sector, together with the more personalised approach to mortgage underwriting.
“The strong finish in Q4 bodes well for lending early in 2019, subject to the outcome of Brexit and consumer sentiment in the run-up to 29 March.”