Late Tuesday morning, Trump stepped onto the roof above the press briefing room and west colonnade that walls the Rose Garden.
He spent nearly 20 minutes surveying the rooftop and the grounds below, including a newly paved makeover of the Rose Garden.
Reporters, tipped off by the out-of-the-ordinary positioning of snipers above the Oval Office, shouted questions from below.
One called out: "Sir, why are you on the roof?"
"Taking a little walk," Trump shouted back.
"It's good for your health."
Trump walked with a small group that included James McCrery, architect of the newly announced $US200 million ($A309 million) ballroom project.
They moved slowly, with Trump frequently gesturing and pointing at the roof and grounds.
Several times, he wandered toward the corner nearest the press corps, waving and cupping his hands to shout responses to shouted questions.
At one point, he said he was looking at "another way to spend my money for this country."
Later, near the end of his appearance on the roof, Trump was asked what he was going to build.
He quipped: "nuclear missiles".
The unexpected walk on the rooftop comes as Trump looks to leave a lasting footprint on what's often referred to as the People's House.
He has substantially redecorated the Oval Office through the addition of golden flourishes and cherubs, presidential portraits and other items and installed massive flagpoles on the north and south lawns to fly the American flag.
And last week, his administration announced that construction on a massive ballroom will begin in September and be ready before Trump's term ends in early 2029.
While Trump appeared on the West Wing, the White House has said the ballroom will be where the "small, heavily changed, and reconstructed East Wing currently sits".
While rare, there have been times through the years when presidents ventured out onto — and even slept on — the White House roof.
To promote renewable energy, President Jimmy Carter installed 32 solar panels on the West Wing roof in the 1970s.
The panels were removed during the Reagan administration.
In 1910, President William Howard Taft had a sleeping porch built on the roof to escape Washington's hot summer nights.
