Even by Lower Mainland standards, a 361 per cent increase in the assessed value of a house in one year is remarkable.

But such a staggering jump — and the tripling of property taxes that comes with it — wasn't grounds for a successful appeal of the North Vancouver property's 2016 assessment.

The homeowners argued the modest two-bedroom, 744 square-foot house, in their family since the 1980s, was reasonably valued at about $1.2-million.

But B.C. Assessment said recent changes to the district's Official Community Plan changed everything — and even though the 19,500 square-foot property hasn't been rezoned and redeveloped, it could be.

In a recent decision, the Property Assessment Appeal Board agreed, and the property's nearly $4.5-million valuation stands.

"This happens constantly throughout Metro Vancouver," said Paul Sullivan, a senior partner at Burgess Cawley Sullivan, a real estate appraisal and property tax firm that did not work on this case.

"If the value of the land increases, due to [plans for] density, then that's what your new assessment looks like."

The property in question, at 440 Mountain Highway in the District of North Vancouver, is 19,550 square feet with a one-storey plus basement single-family dwelling. (B.C. Assessment)

'Ideal for assembly'

The property in question, at 440 Mountain Highway, has one small house with a basement built in 1949 — and is currently zoned for just one single-family dwelling.

The appellants' parents bought it in 1985, according to the appeal documents, back when the price was just $123,000. It is currently an investment property.

In 2015, the value was assessed at $967,100.

But the large chunk of land also sits next to a nursery, near other shops, and right in the middle of a neighbourhood slated for transformation into Lynn Creek Town Centre, under changes to the district's Official Community Plan made in 2011.

Last year, based on other sales in the neighbourhood, assessors decided that makes the single-family home attractive to developers — to the tune of $4,457,000.

The long, narrow property isn't well designed for development on its own, but would be "ideal for assembly" with nearby properties, which the municipality would likely allow, the assessor said in its submissions to the board.

"The property is, in fact, within the 'heart' of the designated Town Centre," the board's decision states.

Highest and best use

In their appeal, the owners argue that the current use and current zoning support a value in the million-dollar range.

Assessing the property based on the Official Community Plan speculates on the "future value of the property without taking into account any risks at all," the owners submitted.

But that's not how it works, the appeal board ruled.

"Much of the appellants' disagreement with the assessment flows from their assertion that the property should be assessed based on its current use. This is not correct," the decision states.

Rather, properties are judged based on their "highest and best use."

Case law has established what that means, said Sullivan, where the "highest and best use" is determined in part by what's physically possible and financially feasible on a site, with a greater than 50 per cent likelihood of being approved.

"Often value increases precede zoning change," he said.

In many parts of Greater Vancouver, property assessments on a typical single-family home are expected to rise 30 to 50 per cent, according to B.C. Assessment. (Rafferty Baker/CBC)

Nearly $13K tax increase

And with that added value comes a big bill — for 440 Mountain Highway, property taxes nearly tripled, leaping from about $5,600 to $18,501.47 in a single year.

Homeowners worried that the march of densification might bring the same kind of tax bill their way should know there is a caveat, said Sullivan.

"The beautiful thing for a homeowner is ... where it's their principal residence for 10 years, [they] are sheltered from this type of change," he said.

"You may only be assessed in your existing use, rather than the assumption of a different use."

That does not apply to the North Vancouver property because it is rented out.

There are restrictions on this type of relief, and homeowners must apply by Jan. 31 to be eligible.