The two-storey, 2,200-square-foot (204 square metres) house retains the basic shape of its original design, but its overall form has been simplified.
Waechter Architecture's goal for the renovation was to create a "modern sculpture," according to the firm.
The red colour, which the architects chose with the client, "gives the house a strong character and identity," Ben Waechter, head of Waechter Architecture, told Dezeen.
They selected the colour based on what was available commercially in sheet metal. The architects then had a local company make the standing seam roof and gutters out of the colour-coated metal and painted the wood siding to match.
The number of windows has been reduced and the shape has been changed from double-hung rectangular windows to single-light squares. Many of the windows were recessed, some by nearly two feet.
The front facade of the house was also flattened with two slanted walls on the ground floor filled in to create a single plane.
The design preserves the "memory of the original balanced with freshness and vitality of the new," said Waechter.
Inside, a similar process of simplification opened up the floor plans, so each level has one large room with smaller support spaces arrayed around it.
On the ground floor, the living, kitchen, and dining areas are located in the main space. The walls are lined with all-white floor-to-ceiling bookshelves. "The project could also be called House for a Book Lover," said Waechter.
The white shelves and ceiling contrast with the refinished fir floors and the colourful spines of the books.
A small bedroom, a bathroom, and a staircase are all arranged around the main space.
The upper floor contains a bedroom and sitting room, separated by sliding doors. Large storage closets and a second bathroom fill the remaining space.
Waechter has designed other monochrome houses in Portland, including an all-white house inspired by the legs and top of a dining table, and a house with a black exterior set on a steeply sloping site.