A further sign the property market could be cooling, with ASB Bank now saying house price growth is likely to be slower than the Reserve Bank's revised forecast.

Latest figures show turnover dipped almost five per cent between July and August...allowing for seasonal adjustments.

And it's taking longer to sell, the average time is now 39 days, up from 36.

ASB senior economist Chris Tennent-Brown says turnover is down 16 per cent on a year ago, and nearly 20 per cent lower than the average level since 1992.

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"What it looks like to us is the peak period of house price appreciation is definitely behind us.

"Nationwide, house price appreciation was running at close to 10 per cent last year whereas it's more like 5 per cent now."

Tennent-Brown says it remains to be seen how sales go in the busy months of October and November.

"Particularly now that the Reserve Bank's on hold and we're seeing some of the longer term rates coming down a little and getting fairly competitive. That'll be interesting to see just how much spring activity that stimulates."