1) Migration. Immigration from outside the country, but also internal immigration within the country from less economically vibrant parts to more economically vibrant regions.
2) Falling interest rates keeping the monthly mortgage payment the same or lower despite higher principals
3) Expectations that the price trend for homes will continue to look like the past. This expectation can lead to people buying more housing than they would normally consume.
4) Shrinking household sizes. You have gone from an average household size of 3.33 in the 1960s to an average household size of 2.53 today. That may not seem like much but you would need ~25% more housing today to accommodate the same population.
5) Larger house sizes. From a median of about 1000 sq ft in 1950 to 2300 sq ft today.
The above can combine to keep pushing up house prices in some areas (as we see in the US) even as the population growth of a country stagnates.