National Australia Bank continues to grow at well above system in the home loan market. Australian Prudential Regulation Authority data shows that NAB increased its home loan book by 0.8 per cent in July - twice the rate of growth of housing credit overall.NAB has maintained this rate of growth, at double system, across the last three months.The primary driver of this growth may still be third-party home loan origination, through the bank's Advantedge division, rather than growth through the bank's own branches and direct channels. Advantedge, for example, is the funder of NAB's UBank branded home loans, (a product launched in late May).Bendigo and Adelaide Bank also reported growth at around twice system over the last three months, though the bank's relative growth rate was 1.5 times system in July.Commonwealth Bank continues to grow at below system in the mortgage market. CBA has lost market share in home loans each month since April 2010.Westpac followed a similar trend for most of this time but has stabilised its market share over recent months.