Hundreds of projects across Ontario now face delays and potential overruns after a strike by more than 25,000 union construction workers.

In the biggest show of defiance, 15,000 union carpenters across Ontario who work on commercial, industrial and institutional projects walked off the job on May 9, joining roughly 10,000 other union members from other trades who had gone on strike during the first two weeks of May.

Inflation and the overall high cost of living in the Toronto area and across the province were factors in the strikes, the largest wave of labor unrest since the late 1980s, said Mike Yorke, president and director of public affairs and innovation at the Carpenters District Council of Ontario.

In fact, the strikes happened after workers at several bargaining units rejected the terms of the latest three-year labor agreement negotiated by union officials and construction industry leaders.

Contractors had agreed to boost pay by 9.5% for workers in the Toronto area, and 9% for workers in the rest of Ontario.

But in the middle of the talks, Statistics Canada, a federal agency, released its monthly inflation numbers, reporting a 6.7% increase in inflation in March, an increase from 5.7% the month before.

Given the rise in costs, workers voted against ratifying the agreements, arguing the increase would be mostly gone after the first year of the contract given the rising inflation rate, according to Yorke.

It’s not just the cost of food and fuel, but housing and other necessities that are weighing on construction workers in Toronto and across the province, Yorke said.

“I think the circumstances of the times we are in – we are in a crisis of affordability,” Yorke said. “Right now the cost of living is through the roof–it’s housing, rental housing, the cost of groceries to put food on the table.”

The carpenters, in turn, are just the latest group to go out on ne strike, with a number of other trades having walked out over the first two weeks of May, he said.

These include the operating engineers, Local 793, a group that includes a range of workers, from operators of cranes and earthmoving equipment to surveyors, and members of the Laborers International Union of North America, including house framers, tilers, carpet and hardwood installers.

“Construction workers across the whole industry are speaking loud and clear we need a solution to the crisis of affordability,” he said.

However, Andrew Pariser, vice president at the Residential Construction Council of Ontario, said the strike will lead to delays and then cost overruns at potentially hundreds of job sites and projects across the province.

Ontario, and Toronto in particular, are in the midst of a building boom, with more than 200 tower cranes at work across the city and numerous rail, roadway and other infrastructure projects underway as well. “As soon as our schedule gets out of whack, costs start to go up,” Pariser said.

Acknowledging the strikes are the most serious since the 1990s, Pariser said approximately 20 union bargaining units had reached a deal, compared to the five or six on strike.

If no deal has been reached on the residential side by June 15, arbitration will automatically kick in, Pariser said. But Yorke, the union carpenters’ chief, said there is no such arbitration rule covering workers on the commercial said.

The carpenters’ union is ready to begin talks, but has been told contractors are not ready to discuss anything yet and are still gathering their numbers, Yorke said.

“We want to get back to the bargaining table and get people back to work,” he said.