John Tiedemann Incorporated (JTI)

JTI is a three-generation family-owned company that has specialized in restoring historic buildings for more than 50 years, with much of its work focused on flat and ornamental plaster. While JTI continually pushes the envelope for new ways to improve restoration and conservation techniques, the company is also proud of its enduring technological developments such as its proprietary telescopic lifts that enable the repair of damaged plaster without the intrusive and expensive use of scaffolding.


Now headed by Ray Tiedemann, who grew up in the liturgical plastering and painting trade with his father and uncles, JTI has expanded its scope to include national historic site preservation work. In the process, JTI has put together a talented staff of designers, plasterers, painters, faux finishers, artisans and fine artists who bring experience, skill and passion to every job we undertake.

Rod Stewart of HPCS and Ray Tiedemann of JTI have now formed a team to bring together their combined expertise, experience and technology to the historic conservation community in the United States.

Historic Plaster Conservation Services Limited (HPCS)

HPCS is an award-winning Canadian architectural conservation firm with a distinguished record in large plaster conservation projects. Its work is based on the methods and formulations developed by Morgan Phillips, a seminal figure in developing the field of architectural conservation in America.


Rod Stewart, president of HPCS, has spent much of his professional career refining Phillips’ consolidation recipes and developing new application methods for the conservation of historic plaster. The result is a remarkably effective method of consolidating (solidifying) and re-keying plaster ceilings. The HPCS system is unmatched in the conservation community. HPCS is always on the lookout for opportunities to experiment with techniques and materials that will extend the useful service life of historic plasters and stuccos.


Visit the HPCS web site at:

© John Tiedemann, Inc.