The Globe’s Real Estate Beat offers news and analysis on the Canadian housing market from real estate reporter Tara Perkins. Read more on The Globe’s housing page and follow Tara on Twitter @TaraPerkins.

An economist at Canada’s biggest bank says home prices could start falling in 2016 if interest rates return to more normal levels. And he warned that, in the meantime, what goes up will likely come down if salaries and incomes don’t keep pace.

“The higher home prices get relative to income by the time rising interest rates really start to bite, the more prices will have to adjust (downwardly) over time to keep longer-term affordability from reaching intolerable levels,” Royal Bank of Canada economist Robert Hogue wrote in a research note Wednesday. “This means that any price increases exceeding the rate of household income gains in the near term (2014 and 2015) likely would result in steeper price declines down the road.”

Mr. Hogue is now expecting sales to tick down by almost 1 per cent next year, and home prices to rise by just 1.1 per cent (he is expecting prices to rise 4.3 per cent this year). That’s actually a stronger forecast than he released just two months ago, because low mortgage rates have been giving the housing market more fuel than expected. He’s now cautioning that too much momentum could be a bad thing for the market long term.

He believes that the current low level of interest rates is not sustainable, and that longer-term rates could rise meaningfully by late 2015 (RBC expects five-year Government of Canada bond yields to more than double to 3.30 per cent by the end of 2015. Five-year fixed mortgage rates tend to move in step with five-year government bond yields).

Rising interest rates will erode housing affordability, which Mr. Hogue notes is already stretched in some markets. “We expect the current upward momentum in home prices to wane gradually, as demand cools and more home sellers emerge,” he wrote. “We expect that the current condo construction boom in large urban centres will bring more properties on the resale market as units are completed. While the majority of condo units under construction are already sold, rapid increase in the stock of existing condos is likely to create a displacement effect whereby older units are vacated in favour of newer ones.”

Looking across the country, he expects a decline in the number of homes sold next year everywhere except in Atlantic Canada and Alberta. “High-priced British Columbia (mainly Vancouver) and Ontario (mainly Toronto) markets are projected to see the bigger drops (2.3 and 1.3 per cent, respectively), reflecting a more extensive erosion of affordability,” he wrote. “We forecast the resale declines in the other provinces to be modest to marginal.”

As for prices, he is forecasting a significant slowdown in the rate of growth next year everywhere except across Atlantic Canada, with Quebec likely to see a small decline in prices.

“Prices in B.C. and Ontario are forecasted to show greater moderation since this is where these negative pressures will be more intense,” he wrote. “Alberta remains at the top of our rankings for next year thanks to its strong economy and in-migration keeping the demand-supply equation still somewhat tight. We expect prices in Atlantic Canada to continue to track a slight upward trajectory.”