President Donald Trump wants to move ahead with his plans to build a Mexican border wall, and while the project is already facing many challenges (such as a lack of funding), other challenges worth nothing are the tight labor pool and rising costs in the construction market.

There is already massive competition in the industry as oil and gas producers lure as many workers as they can with much higher wages. And construction material costs are rising along with wages. Hourly construction pay rose 3% from last year to $28.42 per hour and it is getting even more expensive to build, Bloomberg reports. Construction starts, backlogs and pipelines are all within cyclical highs, but a lack of labor is stalling efforts, JLL states in its Construction Outlook report.

Another important fact worth noting is the large number of undocumented workers that make up the construction labor pool. According to the Workers Defense Project, around half of construction workers in Texas are undocumented while 14% nationwide aren’t legally allowed to work in the U.S., Bloomberg reports. With two-thirds of construction firms around the country having difficulty finding workers, an Associated General Contractors survey says, it won’t be easy finding thousands of legal workers to build the 2,000-mile wall. [Bloomberg]