Canadian housing activity continues at a bustling pace, but there are glimmers the market is set to cool.

Housing starts rose at an annualized pace of 201,700 units last month, Canada Mortgage and Housing Corp. said Monday, though gains in multi-unit construction masked the first sizable slide in single-unit activity in a year.

A separate survey showed fewer Canadians have firm plans to buy a house. And resale activity is already slowing.

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Most economists - including Bank of Canada officials - expect the housing market to slow from its torrid pace. Rising interest rates, tighter mortgage rules and a new sales tax in Ontario and British Columbia will likely dampen activity in the second half of this year. And though monthly numbers - especially in the building sector - can be volatile, economists said the drop in single-family homes suggests the sector is already softening.

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"Is this a signal that single-market construction activity will ease going forward? Probably," said Yanick Desnoyers, assistant chief economist at National Bank Financial.

Quarterly growth in the housing sector is cooling "rapidly," and he expects the sector will actually have a negative impact on Canada's economy next year.

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Higher interest rates are a chief reason for the expected slowdown. The Bank of Canada is widely expected to boost its key lending rate next month. "The sensitivity of Canadian households to interest-rate hikes is very, very high right now" because debt levels of many households have far outstripped personal-income growth, Mr. Desnoyers said.

The resale market, meantime, also points to some moderation as activity has eased from record levels and more supply is coming into the market, the Canadian Real Estate Association said in March.

Canadians seem set to take a breather. Just 3.4 per cent say they are very likely to buy a house in the next 12 months, "suggesting activity may slow during the remainder of this year," a Canadian Association of Accredited Mortgage Professionals report said Monday.

To gauge the effect of rising rates, the association simulated the impact of mortgage-rate increases up to 5.25 per cent. The current average mortgage rate is 4.02 per cent among households that locked in fixed rates during the past year.

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It found that about 375,000 mortgage holders "are already challenged" by their current payments, and an additional 475,000 might be in trouble if their rate hits 5.25 per cent.

Mortgage rates have already risen, though several banks - including Royal Bank of Canada on Monday- trimmed some rates in recent days. RBC's five-year closed rate is now 6.10 per cent - still higher than several months ago.

CMHC's report showed multiple starts rose 27.2 per cent. Single urban starts tumbled 12.7 per cent - the first big drop since last April.

Starts climbed 16.4 per cent in British Columbia, 6.7 per cent in the Prairie region, 4.5 per cent in Ontario, and 1.1 per cent in Quebec. They fell 3.3 per cent in Atlantic Canada. The country needs a pace of about 175,000 to 185,000 units a year to keep up with demographics, economists estimate.

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Canadian mortgage numbers

5.55 million

Number of mortgages in Canada, out of a total 9.3 million homeowners in the country.

$138,000

Average outstanding principal.

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$770-billion

Outstanding mortgage principal on primary residences in Canada.

0.45%

Portion of Canadian mortgages in arrears as of February.

Sources: Canadian Association of Accredited Mortgage Professionals, Canadian Bankers Association.