It wasn’t what one would call a true build-to-suit office project, but the property at 21 Roszel Road in West Windsor essentially became one as soon as Hill Wallack LLP signed on as an anchor tenant.

Just ask Michael Allen Seeve of Mountain Development Corp.

“It was very much a build-to-suit in the sense that we worked cooperatively with Hill Wallack’s team — from (the beginning) of their interest in the building — to try to change or try to incorporate as many of their design objectives into our development plans so that it was reflected in the final product,” Seeve said.

The deal with the law firm paved the way for Seeve’s firm and Gottesman Real Estate Partners to break ground early last year on the 62,500-square-foot building. And as the team markets the last bit of space at the three-story property, they hope to repeat that strategy for a neighboring site at 19 Roszel Road.

It’s a strategy that hinges both on timing and capturing demand from small and midsized office tenants in the Princeton submarket. Seeve, president of Mountain Development, said the first phase of “Roszel Square” was fully entitled when Hill Wallack expressed interest; from there, the developers were able to deliver the building in only a year while having to seek only “ancillary approvals” related to the start of construction.

“To the extent — for things like landscaping — that there was an opportunity for Hill Wallack to weigh in, they did, and the town was extremely cooperative,” Seeve said, also pointing to the application for the firm’s signage on building. “We didn’t have to make any substantive changes to the existing approvals, (such as) something where would have to open it up and really start from scratch, and that was something we wanted to avoid because a big part of the project was its timeliness.”

It also helped that Hill Wallack, which now occupies about 48,000 square feet at 21 Roszel Road, was “focused on the project from the get-go. They were very decisive, they were very organized about what they wanted and we all worked very well together to move through the decision-making process very quickly,” Seeve said.

After signing a subsequent 9,000-square-foot lease with a firm known as Ripen eCommerce, MDC and Gottesman said there is just one 4,000-square-foot space left at the building. And the venture is now hoping to lure a tenant of at least 20,000 square feet to anchor 19 Roszel Road, which is also entitled and will total about 38,000 square feet, before starting construction on the adjacent second phase.

Seeve noted that both 21 and 19 Roszel Road are smaller and “much more human-sized” than the typical build-to-suit projects in New Jersey, which are often reserved for larger companies with sophisticated real estate departments. But he said the types of tenants in the Princeton submarket — even the small and midsized ones — are drawn to the features of new construction as a means of staying competitive.

Specifically, “the companies that will lease space from us are the companies that will put a real premium on light and air in their space,” he said. He pointed to Hill Wallack and Ripen, noting that “good candidates for that are both law firms and e-commerce because they constantly need to attract and retain top people, so a top-quality work environment is an important ingredient in being a really desirable employer.”

And for a developer, the quality of the market allows it to make economic sense.

“I think you can’t help but be impressed with the kind of companies global and regional that choose to put their offices here,” Seeve said. “And as a result of having so many great companies, as a result of being such a great community, the rents are at a level that it does justify new construction.”