Team


Dimitri Nassis
Director of Development
Dimitri co-founded Tandem and lead the development team. After graduating from UIC, he began his career as an options trader on the floor of the CBOE before moving into real estate. Today, he focuses on acquisitions, capital raising, business development, and expanding Tandem’s ever-growing network. Most recently he guided the company’s expansion into Florida.


Tony Andrews
Director of Construction
Tony is Tandem’s co-founder and leads the construction team. With nearly 30 years in the industry, and starting his career as a carpenter, he brings a wealth of hands-on experience to every project. He oversees operations, manages finances, and works closely with project teams to ensure clarity, efficiency, and quality. Known for a practical, solutions-driven approach, Tony has an uncanny knack for simplifying even the most complex challenges and keeping projects on track.
Tandem began with a simple idea: build on trust, respect, and the belief that real estate works best when every discipline works as one. What started as a single project quickly grew into a portfolio that proved the value of combining development, construction, and property management under one roof. Over time, that approach became our platform — fully integrated, deeply collaborative, and grounded in accountability.
Today, a team of more than 20 brings the same hands-on mentality and entrepreneurial spirit that defined our early days, working together to create projects with integrity, character, and lasting value.


Jeffrey Hreben
Senior Development Manager
Jeffrey brings a strong planning and design background to Tandem’s development team. A graduate of the University of Chicago, the University of Pennsylvania’s School of Design in Urban Planning and the Wharton School, he joined Tandem in 2012 and manages efforts across all including zoning & entitlements, design & programming, marketing, and asset & property management. Known for his steady commitment, Jeffrey has been a consistent presence for strategic initiatives and visioning Tandem’s projects from concept to completion.


Paterson Cox
Senior Project Manager
Pat joined Tandem in 2015 after earning his B.S. in Construction Engineering with a Management minor from Purdue University. Since then, he has led the field team on Tandem’s largest developments, bringing expertise in scheduling, site logistics, lean construction, and team leadership. Known for his no-nonsense engineering background, Pat takes a clear and practical approach to solving challenges and keeping projects on track. Dedicated and detail-oriented, he ensures projects are delivered with speed, efficiency, and quality.


Kevin Henning
Project Executive
Kevin joined Tandem in 2017 and brings deep technical expertise as a licensed Structural Engineer. Originally from Green Bay, he earned degrees in Civil Engineering from Case Western Reserve and Illinois Tech. Over his career, he has overseen the design and construction of more than 2,000 residential units along with major healthcare, education, and sports facilities. At Tandem, Kevin focuses on due diligence, budgeting, scheduling, logistics, and overall project execution.


Justin Kleifield
Development Manager
Since joining the team in 2022, Justin supports Tandem’s development initiatives with a focus on project financials and underwriting, legal matters, investor relations, capital markets, and market analysis. He earned both his B.A. and M.S. in Accounting from Indiana University and previously worked with Stage Equity Partners, Dayton Street Partners, and Lakeshore Management.


Chris Walsh
A.L.A, Principal Architect
Chris is Tandem’s Principal Architect, bringing experience in both design and construction. A graduate of the University of Illinois at Chicago, he previously worked at one of the country’s largest architecture firms and later as VP of Architecture for a national homebuilder. A fixture at Tandem since the beginning, he bridges construction, development, design, and engineering to ensure clarity and efficiency.


Kimm Donnelly, CPM®
Director of Property Management
Kimm leads Tandem’s property management team, bringing more than 20 years of multifamily experience. Before joining Tandem in 2022, she spent over two decades with Draper and Kramer where she oversaw a wide-ranging portfolio that included affordable, student, and senior housing, as well as retail. She earned her B.S. in Business Administration from Southern Illinois University and holds an Illinois Real Estate Managing Broker License. Active with IREM, she has served as Chapter President and Regional VP.