The mutual attributed this to higher levels of redemptions as customers sought more rate certainty and looked to lock in longer-term fixed rates.
Mortgage balances have remained stable at £46.6bn. This is the same as year-end.
Profit before tax during the period rose to £158m, compared to £124m in the first half of last year.
The lender saidthis had been supported by the increases in the Bank of England’s base rate, which had improved its margin and income performance.
The average loan to value for the mortgage portfolio fell to 48.6 per cent, which is down from 50.9 per cent at year-end. The lender said this was due to continued growth in house prices.
The mutual continued that management expenses were £139m, up from £124m in the same period last year.
This was driven by £15m increase in costs, which consisted of £8m in spending on strategic investment programme and £7m rise in day-to-day running of the business.
Total spend on investment programmes came to £47m, up from £44m in the same period last year. The programme is modernising its services by redesigning it branch network, implementing its new mortgage platform and improving its digital platform.
Coventry BS said there were “indications of improvements” in the market, pointing to the stabilisation of margins, and it expected to see growth in the second half of the year.
Steve Hughes, chief executive of Coventry Building Society, said it had taken a “deliberately cautious approach” to lending due to “uncertain market condition and competitive margin pressures”.
He added: “As we look ahead to the next six months, it is likely that demand for mortgage borrowing will continue to focus more on re-mortgages as home-owners seek certainty in what has become a very uncertain world. Ensuring that we remain a safe and secure place to save and borrow remains our priority, as is our focus on exceptional service and investing in the society’s future.”