Some remarks made at an investment conference in Sydney yesterday, by RBA governor Glenn Stevens, have been interpreted by market economists as a mild warning against a housing bubble.After outlining global trends, Stevens turned his attention to Australia and noted that "one force helping household and business confidence has been a positive trend in asset markets", including house prices, with the net worth of households going up by 15 per cent since the end of 2011.He went on to add: "Some rise in housing prices is part of the normal cyclical dynamic; it improves the incentive to build, and a price rise reversing an earlier decline probably isn't something to complain about too quickly. Moreover, credit growth, at between four and five per cent per annum to households, and less than that for business, does not suggest that rising leverage is so far feeding the price rise. Hence, it has been a little too early to signal great concern."However, as David de Garis, senior economist at NAB observed, Stevens "fired a warning shot" that central bank tolerance is not unlimited. The RBA expects credit growth to pick up, and will be paying "close attention to" these trends, he noted.Stevens advised lenders and borrowers to exercise "due care".  The RBA wants to see decisions "based on sensible assumptions about future returns. That's what we need if we are to experience a long and sustainable expansion in housing investment that houses our growing population at acceptable cost, and pays reasonable returns on the capital deployed. That's the sort of outcome we want, as part of the more balanced growth path for the economy we are seeking over the years ahead," he said. Justin Fabo, head of Australian economics, corporate and commercial at ANZ, commented: "This appears to be a veiled comment that the bank won't tolerate a period of very rapid house price appreciation, particularly if it is absent a strong and sustained pick-up in housing construction activity."Stevens also conceded - as has been earlier suggested - that the high Australian dollar has led to a decline in the value of the RBA's foreign assets, and, hence, a diminution in its capital, "to a level well below that judged by the Reserve Bank board to be prudent". He, therefore, backed the recent decision by treasurer Joe Hockey to strengthen the bank's balance sheet, which "makes it likely that a regular flow of dividends to the Commonwealth can be resumed at a much earlier date than would otherwise have been the case." The full speech is available at: http://www.rba.gov.au/speeches/2013/sp-gov-291013.html