Patrick Sisson at Curbed.com reports on the ground breaking (no pun intended) work of two Vancouver locals~Joseph Dahmen, a professor of architecture at the University of British Columbia, and mathematician Jens von Bergmann of MountainMath Software. They’ve developed the “teardown index” by determining the ratio of land to home value. Relative Building Value, or RBV needs to be 60 to 70% for a new residence “but when the RBV drops below 10 percent, the chances for a teardown increase dramatically.”.
How dramatically? Based upon their formula, the researches estimate that 25% of the current single residential houses in the city could be gone in the next twelve years.
Due to skyrocketing home prices, half of all single-family homes in Vancouver currently have an RBV of below 7.5 per percent, and research showed that roughly a quarter of all single-family homes sales were tied to teardowns. Absent any zoning changes or dramatic shifts in the Vancouver housing market, the tool predicts that roughly 25 percent of the detached homes in the city will be torn down by 2030.
To Dahmen, these findings suggest the city needs to have a serious conversation about zoning and density.“Do we want very limited numbers of units for a certain number of rich people?” he says. “With another million expected to move to Vancouver in the next 20 years, what do we do? This is an example of why zoning needs to catch up with radical changes. Vancouver needs to understand what the city is, not what it was.”
With the index being applied to the “RS” or single family housing zones of the city, the two researchers postulate that these zones contain 68,000 houses and that 40 per cent of the heritage stock has been demolished since 1985. Allowing for multi-family housing in the RS zones would “tip” the teardown index as the profit from several units on a lot would raise its relative value and increase density. And that means thinking about the single family housing zones in a novel, but not unique way.
As Dahmen states “To create the kind of multi-unit, low-rise housing that you see in Berlin, Paris, or Montreal would require letting go of the kind of single-family home that’s sacrosanct in North America.”
Of course there are also environmental cost savings to producing more density on the same lot, and utilizing renovation instead of demolition to produce more units would be favoured. You can take a look at Jens von Bergmann’s interactive map of single family house teardowns here.
Images: The Tyee and Vancouver Real Estate Podcast