In London, this figure rises to 30 per cent, based on 2016 figures from the Office for National Statistics.
In March, the Royal Institution of Chartered Surveyors warned more than 175,000 construction workers could be lost due to a hard Brexit.
However, a push to attract and train more UK-born workers to construction, which has been advocated by a number of industry leaders, is unlikely to produce the necessary results in time, PwC warned.
“In the long run, efforts could be made to fill skill gaps arising from lower EU migration through enhanced training of UK nationals and automation,” the report said.
“But, realistically, such alternatives are unlikely to make up for any large reduction in EU migrant workers over the next five to 10 years.”
The comments chime with those made by Build UK’s new chairman, Mark Castle, to Construction News in September.
The industry has been looking at new ways to attract UK talent.
In September, Kier launched an initiative committing to staff visiting schools as career ambassadors.
PwC’s report also forecast that overall UK GDP growth will slow to 1.4 per cent next year, down from 1.5 per cent in 2017.
“This reflects slower consumer spending growth, offset by some rise in UK exports and public investment,” the report said.
“But risks to growth are weighted to the downside due to Brexit.”