The housing finance market continued its modest upward trend in July, with residential property investors providing the growth.According to Reserve Bank figures released on Friday, the value of investor loans rose by 0.4 per cent in July, and by 5.8 per cent over the 12 months to July.Owner-occupier loans were up 0.3 per cent in July and up 4.1 per cent over the 12 months.Total housing finance commitments were up 0.4 per cent in July and up 4.7 per cent over the 12 months. The annual growth rate has crept up from 4.4 per cent earlier in the year.According to APRA data published on Friday, National Australia Bank has come back to system after its big growth spurt over the past couple of years. NAB's mortgage book grew by 0.4 per cent in July.Among the other majors, ANZ's book grew by 0.5 per cent in July and Commonwealth Bank's grew by 0.4 per cent. Westpac recorded below-system growth of 0.2 per cent in mortgages in July.Citibank, Bendigo and Adelaide Bank, HSBC, Macquarie Bank and Teachers Mutual Bank all recorded above-system growth in mortgage lending in July.