Once again, the low interest rates are probably an important factor. Houses, like other assets, generate an expected stream of future benefits. With low interest rates, these future benefits are discounted less heavily, which raises the asset’s price today. Low interest rates also push up house prices by boosting the demand for housing.
Of course, some of that increased demand is being met by the rapid pace of construction of new housing. But building houses takes time, and in the interim, higher demand will push up the price of existing houses.