A move by Teachers Mutual Bank at the end of 2013 to enter the third party mortgage distribution market has paid dividends, with the group reporting 12.3 per cent growth in its home loan book over the year to June.The rate of growth of the A$3.8 billion book was well ahead of system growth of 7.3 per cent over that period.Teachers Mutual Bank chief executive Steve James said the group was selling through 12 aggregator groups and a total of 1000 brokers."We think we will have close to 2000 brokers accredited over the next 12 months," James said.He said Teachers had been able to maintain its margin and its credit quality, despite the move into the broker market.He said Teachers' systems had been able to handle the increase in volume without compromising turnaround times and it offered brokers a few points of difference, including an offset on all mortgages that operates through the customer's normal transaction account.Strong growth in its mortgage business helped Teachers increase net profit by 15.4 per cent in the year to June. The mutual bank made a net profit of A$29.8 million and grew its asset base by 10.6 per cent to $4.9 billion.One issue for Teachers has been that it sells a lot of investor mortgages. According to Australian Prudential Regulation Authority data its housing investor book grew by 26.8 per cent over the 12 months to June.James said: "We have been working with APRA and it is happy with what we are doing."The investment lending part of our business will slow but we have some things going on with the owner-occupier business that will keep us growing."Another likely source of growth is Teachers' merger with the Perth-based credit union Unicredit (now Unibank), which was finalised in August. Unibank specialises in servicing the tertiary education sector (not an area of strength for Teachers) and has 7500 members."There is enormous opportunity there. All Teachers Mutual Bank's products and services are now available to Unibank members." Teachers reported that its capital adequacy ratio at the end of June was 15.7 per cent, unchanged from last year.The charge for bad and doubtful debts fell from $2.7 million in 2013/14 to $2.6 million in the year to June.