Divide and build: Denver homebuilder has duplex lots in mind for new single-family homes

Wolff House owners Aaron Koski and Kassi Pelley pose in front of two homes on Mariposa Street that the couple built after subdividing a former duplex lot. (Sara B. Hansen/BusinessDen)

Kassi Pelley and Aaron Koski want to build twenty to thirty new homes in LoHi over the next seven years.

The owners of Wolff House, a Denver development and design firm, hope to replace older duplexes by subdividing their lots and building two houses.

“There is a huge demand for infill products,” Koski said.

Denver will allow the lots to be subdivided if they are at least 50 feet wide, Koski said.

“We understand the administrative process of doing this, which will reduce processing time,” he said.

Their first project with that plan has been completed at 3640 and 3642 Mariposa St. The couple listed the homes in early April for $2 million each, and 3640 is under contract; 3642 is available.

The partners describe 3642 Mariposa St. as “Coastal farmhouse meets Tudor elegance” and say the classic Tudor design inspired them to create the home, which features a pitched roof, muted color palette and large windows that fill the home with light.

The 3,300-square-foot home includes six bathrooms and five bedrooms, one of which could be an office. Custom touches include Fisher & Paykel and JennAir appliances in the kitchen and $25,000 in window coverings to ensure privacy and light control.

Pelley uses her design skills to give the homes a luxurious look.

“We want it to look like a custom home and not a specialty home,” she says.

The house has a small backyard with artificial grass and a detached garage for two cars. (Courtesy of Kylie Fitts)

The primary suite features a fireplace, a seating area, a balcony and a bathroom with underfloor heating and Moroccan terracotta tiles.

The rooftop terrace offers views of the Denver skyline. The small backyard has artificial grass and a detached garage for two cars.

The couple founded Wolff Street in 2013, repairing and remodeling homes before moving into designing and building new ones.

“We were forced to switch to high-quality new construction,” says Koski. “There were fewer opportunities to purchase properties worth the time and financial investment to renovate.”

Initially, Pelley ran the company while Koski worked as a mechanical engineer for oil and gas companies. In 2018, Koski dedicated himself to the company full-time.

To date, the partners have completed 15 projects ranging from $400,000 townhomes to $2 million single-family homes.

Koski said building new homes is riskier but allows the company to control its budgets and make more profits.

The couple wants to build a special structure that looks like a custom home. They want to learn from each project and make the next one more efficient.

For example, they included partial basements in the Mariposa homes, but after hearing feedback from potential buyers, they plan to include full basements.

Wolff House plans to frame future homes with Denver-based Simple Homes to improve efficiency and reduce waste.

Simple Homes, which uses a Swedish-inspired, off-site panel building system, can frame a home in a week, then install windows and doors and wrap the building the following week.

Koski estimates that the partnership with Simple Homes will eliminate three to four months of construction time.

The couple also plans to continue using the basic design of the Mariposa homes to streamline production. They can personalize any home by changing the exterior and selecting different floor plan options.

“If you use a new plan on every home, it’s a new business every time,” Koski says.

“We want to take advantage of the lessons we’ve learned so we can roll it out faster and ultimately lower the price to be more competitive.”