Inspired by Portland’s collection of 1924 tax record photos, Ted Oldham has been busy taking pictures of every single building in the city today.

That’s 20,000 photographs.

Oldham, 72, has already photographed 13,000 buildings and hopes to finish his self-appointed task this spring.

He’s been at the solitary quest for nearly three years. Oldham wants to create a research tool for future historians and a learning opportunity for city residents who want to know what Portland looked like a decade into the 21st century.

His images may not have much value right now, he said, but that value will grow with each passing year. He plans to donate the collection to the city when finished.

Oldham, a semi-retired architect, walks 10 miles a day when working on the project. He said he is amazed how people choose to express themselves through decorating and maintaining their houses.

“Our buildings are a physical expression of what our values are,” he said.

Oldham’s project is a valuable gift to the city, although not many people know about it, said Stephen Podgajny, executive director of the Portland Public Library.

“To me, it’s a very important thing that he’s doing,” Podgajny said. “It’s quietly a very stunning and generous effort.”

Oldham sits on the city’s historic preservation board. That’s where he first became aware of the 1924 photographs taken as part of a tax revaluation. He said they’re a vital resource for anyone restoring an old city building.

He figures his project will take a total of 1,000 hours to complete.

He uses a professional digital SLR camera, a Canon 5D, with a 24 millimeter perspective-correcting lens.

He takes one photograph for each building, at an angle to show both the front and one side — thus getting the most information possible with one photo.

He prefers cloudy days, but it’s hard to avoid sunny days in Portland — the city has 205 sunny days a year, he said.

He doesn’t take photos when there is snow on the ground because the snow covers the bottom of the buildings. He also doesn’t take photos when the trees have leaves because the foliage hides too much. He will not take photographs of children.

Oldham, who lives in the West End, moved to Portland seven years ago from Washington, D.C.

He said he’s impressed by the diversity of architectural styles in Portland, and by the city’s economic diversity. Neighborhoods aren’t separated by income and class in Portland as much as they are in other cities, he said.

“There is very little economic separation here,” he said.

He said he’s also impressed by the pride with which Portlanders maintain their homes, often doing the work themselves.

For the most part, homeowners have been welcoming. Only a dozen people have questioned him about his activities, and they seemed satisfied when told about his project.

Only one man became angry, telling him he couldn’t take photos without a city permit. He was a lawyer.

When the 1924 photographs were taken, photography was a specialty practiced by a few professionals. Today, with cellphones and easy-to-use digital cameras, the world is flooded with digital photographs.

Still, very few people are taking photographs of buildings and neighborhoods, Oldham said. Also, many of the digital photos being taken today will eventually be lost.

“Most images are transient,” he said. “The go in an email and disappear.”

Because this project is so large and ambitious, he hopes his photographs will survive.

“I hope at some point they will have some value,” he said.

Staff Writer Tom Bell can be contacted at 791-6369 or at tbell@mainetoday.com