Our Leadership

We are constantly listening, learning and adapting. That defines what we do.
It is our commitment to sustainability, that defines who we are.
Together, our vision is to create transformative environments, having fun in the process.

Joanne McCallum

Executive Director & Principal


As Co-founder and Director, Joanne provides direction and oversight on a full range of building typologies. Her work is informed by vigorous research and careful client consultation, working from first principles in a way that thoughtfully translates her clients’ needs into physical reality. read more

Michelle Austin

Managing Principal, Operations


Michelle embodies exceptional knowledge and management skills related to the construction process. She is responsible for the firm’s field review services and provides critical peer review oversight on all of our documentation, ensuring projects meet or exceed the firm's exacting standards. read more

Drew Hauser

Director, Design & Business Development

Hons. Vis. Arts, B.Arch., OAA, FRAIC, AIA, CAHP

Drew is an artist, businessman and director here at mcCallumSather. He is passionate about shaping environments that put our clients’ business and research objectives at the forefront, and has been instrumental in providing award-winning design solutions that establish a precedent and are carefully tailored to our clients’ goals. read more

Heather Gordon

Managing Principal, Finance & Administration

CPA., MAcc.

Heather brings years of financial and business experience to mcCallumSather. With her professional Chartered Accountant designation and Masters of Accounting degree, she ensures that all aspects of the business and all projects are managed with financial integrity. read more

William Neal

Principal, Architect

B.Arch (Hons.), Dip.ArchTech, OAA, AANB, MRAIC, PMP, LEED Green Associate

William is a registered architect in Ontario with over seven years of working architectural experience, a hands-on construction background, and a complementary technical degree.  In 2016 he earned his PMP designation, which has helped the firm with its development of more sophisticated project management protocols for the benefit of our clients. Further, his leadership has helped to secure the firm’s exciting growth specifically in multi-unit, high rise residential projects, transportation, and operations centres. read more

Willems Ransom

Principal, Architect - Buffalo Office


Willems is an award-winning leader who is passionate about research and design. He has proven an ability to draw out the best from his integrated teams and it shows within his exciting and diverse portfolio. Each are unique spaces, sensitive to their context and prioritize sustainability. Whether healthcare, education, community libraries or corporate/commercial work, each […] read more

Kevin Van Hartingsveldt

Principal, Project Manager

Dipl.T.(Arch.), LEED AP, PMP

Kevin brings an exceptional attention to detail and technical understanding to each project. Kevin has been with mcCallumSather since 2008, serving clients in the healthcare, institutional, civic, transportation and residential sectors. read more

Liam Brown

Principal, Architect


Our clients appreciate Liam’s systematic and steady approach to his work, and ability to mix creativity with practical solutions in a way that thoughtfully addresses our client’s requirements. His ability to listen, absorb and respond to our clients’ vision has been essential in our success on projects in multiple sectors, specifically his growing portfolio of complex healthcare renovation and specialized lab environments. read more

Mary Georgious

Senior Associate, Mechanical Lead


An enthusiastic leader, Mary offers extensive experience in HVAC, fire protection, plumbing and medical gas system design. As the firm's mechanical engineering lead, one of Mary's specific strengths is in project management and problem solving, ensuring that all mechanical solutions seamlessly integrate into a project's design. read more

Adam McCaughan

Associate, Architect


Adam’s work demonstrates his deep understanding of process. Adam has led LEED Facilitation on projects throughout Southern Ontario and as far east as Newfoundland & Labrador, supported by his understanding of building science. He pioneered the role of Authorities Liaison within the firm, ushering projects through complex approvals processes. As project manager, he has a […] read more

Liz Gabaldo

Associate, Interior Design Lead

B.I.D. (Hons)

Liz is widely recognized for her ability to create beautiful interiors that speak to the unique identities of her clients. Whether a brand identity for her corporate, commercial and retail clients, or a reflection of a family in single family homes. Her designs ultimately become a reflection the way in which her clients live, work […] read more

Ashraf A.Abdullah

Senior Associate, Architect Design Lead

B. Arch., OAA, PMP

Ashraf is a seasoned mentor, teacher and designer, making him the ideal fit as our firm’s design lead. Ashraf has a broad portfolio of work, including residential, post secondary and institutional designs. Our clients have come to know Ashraf for his quiet confidence, eagerness to listen and respond with tailored, well considered design solutions. Our […] read more

David Riley

Associate, Mechanical Engineer


David excels on projects that present a unique challenge, and where data can be employed to shape meaningful design solutions. It comes from his commitment to being a team player, both as a part of and leading teams through the complexities of the design process. His ability deliver thoughtful solutions is bolstered by his project […] read more

Laura Sears (she/her)

Senior Associate, Marketing Lead

B.J. (Hons), MBA

As an integrated member of the design team, Laura leads the firm's strategic communications, from business development to project specific promotion. read more

Greg Sather



Co-founder and Director, Greg is responsible for design direction, sustainable design initiatives and providing technical excellence oversight for the firm’s projects. His experience with the design of high performing spaces has resulted in ground breaking projects and firmly established his reputation as a leader in sustainable design. read more