The Economist analyzes the actual house price boom and gives clear indication to rent instead of buying in these countries. Interesting analysis of a bubble:

"The ratio of prices to rents is a sort of price/earnings ratio for the housing market. Just as the price of a share should equal the discounted present value of future dividends, so the price of a house should reflect the future benefits of ownership, either as rental income for an investor or the rent saved by an owner-occupier. To bring the ratio of prices to rents back to equilibrium, either rents must rise sharply or prices must fall. Yet central banks cannot allow rents to surge as this would feed into inflation. Rents directly or indirectly account for 29% of America's consumer-price index, so rising inflation would force the Fed to raise interest rates more swiftly, which could trigger a fall in house prices. Alternatively, if rents continue to rise at their current annual pace of 2.5%, house prices would need to remain flat for over ten years to bring America's ratio of house prices to rents back to its long-term norm. There is a clear risk prices might fall.

Lower real interest rates might justify a higher p/e ratio. For example, real interest rates in Ireland and Spain were reduced significantly when these countries joined Europe's single currency---though not by enough to explain the whole rise in house prices. In Britain, where tax relief on interest payments has been scrapped, real after-tax rates are close to their average over the past 30 years, and so do not justify a higher price/rent ratio. In America, too, real post-tax interest rates are not historically low, in part because mortgage-interest tax relief is worth less at lower rates of inflation. For instance, if interest rates are 10%, tax relief is 30% and inflation is 7%, the real after-tax interest rate is 0%. If interest rates are 6% and inflation is 3% (ie, the same gap as before), and tax rates stays the same, the real interest rate is 1.2%. "