Old Exchange and Provost Dungeon

Old Exchange and Provost Dungeon: The Old Exchange and Provost Dungeon with new Design Pigmented Mineral Stain finish that emulates lime wash but will last for decades.
Old Exchange and Provost Dungeon
Pictured above: The Old Exchange and Provost Dungeon with new Design Pigmented Mineral Stain finish that emulates lime wash but will last for decades.

About This Project


The Old Exchange & Provost Dungeon, also known as the Custom House, and The Exchange, is an historic building at East Bay and Broad Streets in Charleston, SC. Built in 1767-71, it has served a variety of civic institutional functions, including notably as a prisoner of war facility operated by British forces during the American Revolutionary War. The building was designated a National Historic Landmark in 1973. It is now a museum operated by the Daughters of the American Revolution.


The lime plaster had been restored in 2007 and finished with a lime wash, that was again refurbished in 2011.  The frequent need to repaint was a problem for the museum as they are completely reliant on visitor fees and attendance drops whenever the building is scaffolded.  A mineral silicate finish was selected to deliver an appearance akin to lime wash, but with durability to last decades.  The previous lime wash color had also faded/changed to a yellow ocher color, that is was not historic so a non-fading solution was required.




Challenges Previously lime washed lime plaster had degraded severely and there was significant un-bound pigment on the surface.  The original "Federal" gray had faded and changed color to a shade of yellow ocher, which was inappropriate to the building's history and design.  Severe bio growth and pollution had also streaked and stained the lime wash finish leaving the building with an unacceptable appearance.  Even after thorough steam pressure cleaning much of the unbound pigment was left on the surface, which needed to be consoldiated and "tied-down".



The thick, load-bearing masonry construction and lime plaster required a vapor permeable solution, so latex and acrylic finishes as well as high-build elastomeric finishes were not appropriate. 



In addition, limestone architectural details had become eroded and very porous and required penetrating but breathable water repellent treatment.  
Solutions Potassium Silicate Fixativ was used as a pre-treatment to help consolidate the surface and tie-down loose and unbound pigment that remained after power washing.  This treatment also ensured a more uniform final appearance and helps to extend coverage of the finish coats.



Design Pigmented Mineral Silicate Stain was the solution providing a finish and visual appearance very similar to the original lime wash, but with the added durability provided by the mineral silicate binder.  The system is very vapor permeable and will not trap moisture within the masonry walls.  Because only light-fast pigments are used, the color will never fade or change colors.  Using Design Pigmented Mineral Silicate Stain allows the finish to perfectly follow the contour of the lime plaster adding character to the finish, without sacrificing durability.  It is also a very smooth finish the has a texture identical to lime paint/wash.  



Limestone accents were treated with penetrating Silan 100 Water Repellency which provides excellent resistance to water penetration, but is extremely vapor permeable and did not alter the appearance of the stone.  
Architect HEERY International   www.heery.com
Contractor First Exteriors, LLC, Charleston, SC   www.firstext.com
Applicator First Exteriors, LLC, Charleston, SC   www.firstext.com
Type of Project Historic Restoration
Customer The Old Exchange and Provost Dungeon and The City of Charleston, SC.
Location Charleston, South Carolina (United States)
Regional Info