Super Bowl LI is still 18 days away, but Madison Avenue’s TV ad controversy game has already started.

Fox, which will broadcast this year’s NFL Championship game, has asked for changes to a 90-second commercial from a building supply company because the ad featured a border wall.

The spot, from 84 Lumber, a first-time Super Bowl advertiser, was deemed by Fox to be too controversial, a spokesman for ad agency Brunner told The Post.

In a statement, agency chief executive Michael Brunner said, “Fox rejected our original commercial because they determined that some of the imagery, including ‘the wall,’ would be too controversial.”

The retail chain used the wall image, Brunner said, because it wants to talk about who it is — “a company looking for people with grit, determination and heart, no matter who they are, where they come from, or what they look like.”

The spot featured people peeking from behind a wall in a search for jobs, according to a report in Campaign magazine, which first reported the dispute.

The chain is vowing to tell its story online as well as in the Super Bowl spot.

Fox declined to comment.

The two sides are said to be working toward a compromise — a spot without the wall. The commercial, if approved, is scheduled to air before halftime.

It is hard to decipher at times whether ads are purposely made to rile networks in order to gain media attention.

“The point isn’t to say anything about a political stance one way or another,” said the agency spokesman, adding that the firm was interested in seeing different people’s interpretation of the message.

The founder of 84 Lumber, Joseph A. Hardy III, 94, has built the business into the largest privately held construction materials company in the US, with 2015 revenue estimates at $2.5 billion.

The company gets its name from the town where it is based: Eighty Four, Pa.

Hardy is a colorful character. After his wife of 50 years died, the executive married a 23-year-old manicurist in Las Vegas. He filed for divorce 107 days later.

Seven years later, at 92, Hardy walked down the aisle again — marrying a 22-year-old.

He retired from the business — now run by his daughter Maggie Hardy Magerko.

Companies spent some $2.59 billion on Super Bowl spots during the past 10 years, according to ad measurement firm Kantar Media. The cost of a 30-second spot has doubled in a decade — to around $5 million, Kantar said.

Meanwhile, Anheuser-Busch on Wednesday released some details of its Super Bowl plans.

One ad will feature an outsider — namely, its German-born founder Adolphus Busch. The spot will be dedicated to its discount Busch brand and is aimed at underlining the American dream and celebrating “ambition and hustle,” the company said.

It’s the first time Anheuser-Busch, a regular Super Bowl advertiser, is using its Super Bowl time for Busch beer.

Overall, there were 49 minutes and 35 seconds of ads in the 2016 Super Bowl, Kantar said.