The construction industry in the U.K. is heavily reliant on foreign labor. Post-Brexit rules which will only allow high-skilled workers to live and work in the country permanently will likely cause a shortage of low-skilled labor. Foreign workers who are not classified as “high-skilled” will only be allowed to remain in the country for a year at a time. In the U.K. nearly half of all builders are foreign workers.
See "U.K. Builders See Brexit Crisis When Foreign Labor Disappears", Olivia Konotey-Ahulu, Bloomberg, August 5, 2019