The Halifax, part of Lloyds Banking Group, said that the average home in the UK cost £213,930.
Prices in the three months to the end of August were 0.7% higher than the previous quarter - marking a slowdown in the pace of growth.
Property values fell by 0.2% in August compared with July, the lender added.
"House price growth continued the trend of the past few months in August with a further moderation in both the annual and quarterly rates of increase. There are also signs of a softening in sales activity," said Martin Ellis, housing economist at the Halifax.
"The slowdown in the rate of house price growth is consistent with the forecast that we made at the end of 2015. Increasing difficulties in purchasing a home as house prices continued to increase more quickly than earnings were expected to constrain demand, curbing house price growth."