The University of Virginia is the only US university with a World Heritage designation, it’s conservation is of the utmost importance and is currently undergoing the largest restoration campaign in decades. Matt Wolf and his team from Centennial Preservation are currently working on the repointing and window repairs for the Rotunda at Thomas Jefferson’s Academical Village.
The Chemical Heritage Foundation released an episode of their award winning podcast Distillations. In this episode, Randy Ruth, formerly of LimeWorks.us, discusses the chemistry behind lime mortar, historic masonry buildings and the ongoing efforts to preserve one of the finest works of notable Philadelphia architect, Frank Furness. The 19th Street Baptist Church located in South Philadelphia has been in a state of disrepair for decades. This episode sheds light on the chemistry behind its construction and the ongoing preparation to save it.
Randy Ruth, at the time, was the lab tech at LimeWorks.us. He bridged the gap between architects, conservators and masonry practitioners on what types of building materials to use in reconstruction and restoration of masonry projects throughout the country.
“Randy and his colleagues at LimeWorks.us based in Quakertown, Pennsylvania were brought in to try and save the 19th Street Baptist Church
We took a look at at the types of mortars that were there and by knowing that the building was built in 1874 we could gauge what those original binders were without even necessarily doing an analysis. Architects, engineers and of course masons would use the local available materials which were at the 19th Street Baptist Church primarily lime based binders.
Lime is a very general term for inorganic materials that contain calcium and it’s been use in concrete and building materials since the Roman Empire. It’s derived from limestone and other rocks that are primarily made of calcium carbonate.
Basically lime is that calcium carbonate stone and it’s put into a kiln with fuel. These kilns would then be fired up to 900 degrees Celsius or slightly above and then the resulting product is a limestone that loses about a third of its weight because it’s driving off carbon dioxide so that calcium carbonate is now becoming calcium oxide.
This is all part of what’s called the Lime Cycle. Calcium carbonate is heated to produce calcium oxide and then it’s combined with water to form calcium hydroxide. Different amounts of water is added to form different consistencies.
That process is called slaking, if just a small amount of water is added it’s going to turn into a powder. If a little bit more water is added it’s still calcium hydroxide but it’s in the form of a putty.
Once the lime is in this putty form it’s spread over bricks and stones and hardens into a solid bond.
That limestone then stays malleable and flexible in a wall system in comparison to more modern materials.
Modern materials like cement. Portland cement is the most common type of cement used around the world. It’s made of primarily alite or tricalcium silicate, a more rigid and less permeable material than lime.
You’re walking down the sidewalk and wondering why are they sectioned off in four food squares or six foot squares and that’s because Portland cement is very brittle and we have to tell it where to crack and where to go versus the lime buildings like the 19th Street Baptist Church. There are no control joints and things were able to move freely and accommodate small bits of movement because lime unlike Portland Cement has the ability to heal itself, something called autogenous healing.
This autogenous healing is part of why the 19th Street Baptist Church is still standing today but the original lime mortar is all but dissolved now and that’s why the building is crumbling.
Lime mortars as they age and as they wear, they’re meant to be replaced so there’s always a maintenance issue associated with them. I hope that there is a lot of architectural salvage that can occur to pay homage to the traditional materials that were originally by Frank Furness and his architectural team.
In essence they should be able to replenish the lime mortar in the structure, but after so many years of neglect it’s getting late in the game.”
We’re so proud to be part of an incredible restoration campaign currently taking place at the University of Virginia. The Rotunda is the focal point of Thomas Jefferson’s Academical Village at UVA and we have the pleasure of supplying our Ecologic™ Mortar for the repointing campaign. Below is an excerpt from the university’s website explaining the repairs that are currently taking place, also take a minute watch the brief video.
Preserving the Heart of the Grounds
The capitals atop the Rotunda’s columns were shrouded in protective netting after it was discovered that they were crumbling from age and a variety of other issues.
Thomas Jefferson intended the Rotunda, which he called a “temple of knowledge,” to be the centerpiece of the Academical Village; it housed the heart of the University operations—the library and classrooms. The Rotunda and associated grounds are now in critical need of extensive repairs. The renovation, which began in May 2012, will span several years.
What specific repairs and renovations are being done?
The Rotunda renovation includes extensive infrastructure upgrades and exterior repairs. The initial phases are addressing conditions that threaten the building’s integrity and include significant roof repairs, column capital restoration, masonry repairs, and window restoration. Panels in the Dome Room will be replaced with a better acoustical control system; lightning protection will be greatly improved; and a new elevator installed.
Later phases of the project will entail improvements to the Rotunda’s interior infrastructure and restoration of the surrounding landscape. The building’s aging infrastructure, including plumbing, electrical, audio/visual, heating/air conditioning, and fire protection, will be upgraded. Portions of the building may be adapted to allow for classroom use. The current total estimated cost is $50.6 million.
This beautiful late 19th century Hummelstown brownstone was recently restored by deGruchy Masonry Restoration, the Technical Install/Training Team of LimeWorks.us. Using historically appropriate, breathable Natural Hydraulic Lime based materials for repointing the brickwork and repairing the brownstone, this iconic building is now put into an excellent state of conservation. It remains a testament to excellent stewardship of our built heritage thanks to the owner, and lifelong resident of Middletown, PA, Robin Pellegrini.
Taking an architectural conservator’s approach, the team of masons repaired the broken and missing pieces of historic sandstone and lime mortar with environmentally friendly Ecologic® Mortar and Lithomex Brick and Stone repair material. The team retained as much of the historic fabric as possible by repairing what could be salvaged with these specialty materials. These materials allow the building envelope to process water out naturally through the lime and sandstone because of their effective liquid/vapor transfer properties over any patch material based on Portland cement.
Please take a look at our other videos for the full extent of this remarkable restoration:
For well over 30 years it has been common practice to prescribe the use of a Type-O masonry mortar for use on the conservation of masonry buildings. The most common formula of a Type-O mortar is 1:2:9, a blend of 1 part white Portland cement, 2 parts Type-S hydrated lime (most often dolomitic lime) and 9 parts sand by volume. In recent years there has been an increasing amount of research on similar mix designs and how they compare to Natural Hydraulic Lime (NHL) based mortars used in Europe to repoint historic masonry buildings. Just recently, a professor and two graduates of Columbia University published a research study on the same topic here in the United States. The results of this study can be found in the Association for Preservation Trades International bulletin Vol. XLIII. Their innovative approach to allow a real comparison between different mortar types used in conservation reveals some interesting results.
Petrographic thin section images courtesy of William Revie of The Construction Materials Consulting Group; Striling, Scotland
Petrographic thin section images courtesy of William Revie of The Construction Materials Consulting Group; Striling, Scotland
The innovative approach the research team had developed with their curing protocol of various binder types, established a relatively level field of comparison for various mortars in regards to the way each mortar uniquely cures. With this testing detail established, the 11 commonly used repointing mortars were tested at various stages on their splitting tensile strength, compressive strength, water absorption and water-vapor transmission.
The tests reveal that for a splitting tensile strength the NHL/sand mortars are most comparable to traditional pure lime/sand mortars made of High calcium lime and dolomitic lime, while Type-O mortars were more than twice the splitting strength of NHL mortars. Although anecdotal, the cases where historic pure lime mortar has been used to repoint soft brickwork and has eroded causing a need for repointing, Type-O mortars could be consequently be too rigid for use a repointing mortar.
Compressive strength data shows that although NHL mortars have higher values than that of high-calcium lime mortars (with the exception of NHL 2 being less in strength than dolomitic lime) when compared to Type-O mortars their values are nearly half.
When mortars were measured for their water absorption, initially all NHL mortars significantly out-performed other mix designs. The most comparable mix was that of the Type-O mortars that ended up with similar characteristics to NHL mortars and still outperformed both pure lime mortars.
Water-vapor transmission results indicate that all NHL mortars process water vapor at much higher rates than dolomitic and both Type-O mortars, with values comparable to High-calcium lime mortars.
Although the results from the laboratory study are not entirely representative of values that are obtained in field work, they do represent what specifiers and conservation masons are attempting to achieve in real world situations. By eliminating variables, that can give anecdotal results and margins of error, the data suggests that NHL\’s are indeed appropriate when specifying a historic repointing mortar or a new construction mortar used for masonry mortar, plaster or stucco applications.
In conjunction with this study and the new ASTM C1713 – Standard Specification for Mortars for the Repair of Historic Masonry, Natural Hydraulic Lime clearly proves its self as an alternative to mortar mix designs that have been used widely in the United States for many decades and have shown, for one reason or another premature failure.
This beautiful church was designed by Frank Furness and is located at the corner of 19th and Titan in South Philadelphia. It almost went the way of many Furness structures; due to neglect and time the church leadership is under pressure to begin repairs or plan for it to be demolished due to unsafe conditions sited by the License and Inspections Department of the city. Under the leadership of Reverend Vincent J. Smith and in partnership with the Greater Philadelphia Preservation Alliance and some volunteers, stabilization efforts have finally begun.
As the morning sun crept over the skyline on the last Saturday of April, Randy Ruth, mason and the laboratory technician from LimeWorks.us volunteered to lead a workshop with a team of a few other volunteers to complete some small but crucial repairs on the north facing wall of the 19th Street Baptist Church.
The church has been in need of serious repairs for a number of years as observed and documented in a 2000 University of Pennsylvania report, Thesis by Molly Anne Sheehan, which show that the conditions of the church and the exterior Serpentine Stonework have continued to deteriorate steadily.
Under Randy’s supervision the team of volunteers used a lime mortar donated by LimeWorks.us for doing some in-kind repairs to stabilize the failing back-up walls behind the Serpentine stone. This lime and sand mortar reflects what would have been used originally when the church was constructed in the late 1800s. Ecologic® Mortar contains NO harmful Portland Cement and allows the building to breathe and process water as it did originally. At some point in time, a hard and brittle Portland Cement stucco was placed over a significant part of the building, trapping moisture and leading to further deterioration of the soft, sedimentary serpentine stone and contributing to mold issues that the church basement still has to deal with today.
This was the first step in saving the most colorful building ever designed by Furness… A true master plan is needed for the next step in partnership with strong fundraising efforts to truly bring this sacred place back to its original glory.
Other stories about the 19th Street Baptist Church…
New Orleans. It’s quite the town especially during the weeks leading up to Mardi Gras, known as Carnival. Technically beginning on January 6th and concluding on the day before Ash Wednesday (aka Fat Tuesday), the long celebration is concentrated on the final few weeks, giving rise to more frequent parades and events. Granted I had never been there before but what I expected was much different from my experience. As a Philadelphia native, I had assumed that it’s nothing but one insane party similar to events that might occur during the Mummers parade on New Year’s Day in Philly, and be only on Fat Tuesday. What I had experienced was by far richer in both culture and architectural significance. I don’t mean this to down play the heritage of historically significant Philadelphia. It’s just that New Orleans has a charm that I believe to be facilitated by it organic architectural style, originating in function over form.
Spending most of my time in the oldest neighborhood in New Orleans also known as the French Quarter or as some may traditionally refer to it as Vieux Carré, I felt a certain type of warmth from the people and its buildings. The symbiotic relationship felt I found to be rooted in the architecture bound mostly by French, Spanish and African influence. This dynamic create a true Creole culture. Perhaps this is why nobody can exactly pinpoint the exact year that Carnival festivities began, a very real unique place and people whose origins can be traced to their roots but only studied in regard to its complex organic creation. The trend can be translated to local architecture in the French quarter however it is a bit easier to study.
A New Orleans local showed me around the French Quarter explaining all the influences of Spanish, French, African and local climate on many of the buildings architecture. Probably the most iconic would be the balconies and galleries extending over the sidewalks. Just to be clear balconies are cantilevered into the building with no supporting posts extending halfway over the sidewalk, while galleries typically extend to the edge of the street. Unbeknownst to me I found that the reason for this is threefold.
First, has to deal with the influence of the Spanish and French architects designing buildings since New Orleans beginnings. However, more often than not these buildings needed to be protected from the weather. Wind driven rain during hot summers created the need to have large open windows to permit air flow but something needs to prevent the buildings from getting wet on the inside, hence the need for balconies to act as an eve to prevent rain from entering the interior. The same principle also protects the inferior masonry walls. New Orleans suffers from poor clay local clay for making bricks. The result being bricks called “soft reds & hard tans” that in most cases must be protected with a stucco or render of lime.
What is currently known as the Napoleon house was first occupied by the mayor of New Orleans from 1812 to 1815. Although Napoleon never came he was offered this residence during his exile in 1822.
Detailing of deteriorated “Soft red” brick rendered with lime stucco as a Trompe L’oei to imitate limestone blocks on the Napoleon House.
Another defining characteristic of architecture in the French Quarter is the entresol, also known as mezzanine. Entresol’s were needed for storage in commercial buildings due to the high local water table. Looking at the exterior of a building one can clearly notice the well defined tall window front that help hide the storage floor between the 1st and 2nd floors.
This store front exemplifies the use of an entresol commonly found in the French Quarter.
Due to New Orleans high water table, rising damp is a big issue for many of the building. Because the majority of the historic Buildings located in the Vieux Carré district were built before the advent of Portland cement, lime was used and accommodated moisture very well. However, today pure lime technology is used to restore the local historic properties, which results in fewer lost or damaged cultural resources.
The time I spent in New Orleans was certainly too limited. There was far too much to see in the few days I was there. Its impact left me forever moved by its places and people. For anyone who has not been there. GO! The treasure hidden in the city is everywhere, waiting for people to experience it and take a piece of it home. Perhaps the next time I visit I will see you there.
Damaged stone and brick is a common problem for many historic structures around the world. Lithomex is a breathable in-kind repair material for most types of damaged stone and brick. The following is an example of a Lithomex repair on a historic 19th century stone house…
Lithomex Repair in Merion Station, PA:
This house, located in Merion Station Pennsylvania, near Philadelphia, was constructed in the 1920s during the Arts and Crafts style movement. This movement was a direct descendant of the British Arts and Crafts movement which was initiated by William Morris during the mid 1800s as a reaction to the Industrial Revolution and its lack of concern for human lives in the work place. This movement was meant to bring back pride to the true craftsmen once again with an emphasis on hand-made vs. mass production.
Before applying Lithomex
This house was handcrafted using a variety of stone including Mica Schist, Serpentine, Red Sandstone, Brownstone, PA Bluestone, and some Limestone. It was originally pointed with a high Portland cement content mortar, either 5:1:2 or 1:3 formula of Cement, Lime and sand. Unfortunately this was a recipe for disaster.
During the following 80 years, the softer sandstones received the greatest damage due to the freeze/ thaw cycles of the cold Pennsylvania winters. This combined with later modifications including new windows which were installed improperly allowed water to be trapped behind and within the stone walls. Leaks developed within the house and the homeowners decided it was time to fix things the right way.
Lithomex being applied
A team from Galli Masonry Restorations took on the challenge to bring this historic home back to its original glory. First they removed all the old pointing and filled in the voids with LimeWorks.us Natural Hydraulic Lime mortar. Then blended with Lithomex colors and textures to replicate the original look of the stone. The damaged serpentine, brownstone and bluestone was repaired and blended in to be virtually unnoticeable. The color and composition of the final pointing work was chosen by the homeowner which was a mix of Ecologic® MortarDGM non-pigmented, DGM Grey andblack Slag-fleck.