3rdLine.Studio is a mid-sized architectural practice based in Sudbury, Ontario. Established in 1984 by Dennis Castellan and Peter Dewit, the office has been in practice for over 40 years. Offering a full range of architectural services our built portfolio includes residential, commercial, institutional and industrial work across northern Ontario and beyond. In its 40 years of practice 3rdLine.Studio has built its reputation upon leading, designing and delivering creative architectural solutions that respect both function and finance.

What’s in a name

In 2016, Castellan James and Partners Architects became 3rdLine.Studio. This change in name represents a continued evolution of the practice. We continue to believe in the power and strength of a studio process and open collective effort. We continue to build upon lessons learned and are committed to the delivering successful projects.

The name itself, 3rd Line Studio, is grounded in the elements we have defined as essential to the practice of architecture.


Our Team