The bidding up of existing ones is a side effect that happens however central banks are more about controlling investment in new ones than the price of existing

The bidding up of existing ones is a side effect that happens however central banks are more about controlling investment in new ones than the price of existing ones. Higher prices of houses means there is more incentive for them to be built (or repaired) and for the builders to be paid well. Central banks stimulation is meant to make sure this happens to a sufficient degree, just not so much that builders (and workers more generally) are paid too well that it would drive inflation too high.