Unexpected Discoveries During Drayton Hall's Portico Rehabilitation

By Special Contributor posted 11-20-2015 12:26


By Trish Smith

A year ago, Trish Smith wrote about the work on Drayton Hall’s portico here on the Preservation Leadership Forum blog. We thought it was time for an update.

Drayton Hall from across the pond. | Credit: Wade Lawrence
 Drayton Hall from across the pond. | Credit: Wade Lawrence

Established in 1738 and completed by the mid-eighteenth century, Drayton Hall is the earliest and finest example of Palladian architecture in North America. The most important character-defining feature of this grand edifice, the iconic portico, is the only one of its kind in the world in that it both projects from, and recedes into, the main house. As mentioned in my previous post, physical and documentary evidence abounds that the portico has been plagued by structural issues for centuries with the earliest major repair campaign being carried out in the second decade of the 19th century. While steps were taken to prolong the life of the 20th century concrete, by 2010 it was clear that a more comprehensive solution was in order. Bennett Preservation Engineering (BPE) conducted an in-depth structural assessment and devised a rehabilitation program that would address historic and modern mechanisms of decay as well as long-standing structural issues in the portico. To date—the entire first floor concrete deck has been removed, and a new system of wooden joists is being installed in its place. However, one discovery in particular has raised new questions about the early appearance and phases of construction at Drayton Hall.

In order to safely remove the portico concrete below the columns without undermining their structural support, it was necessary to devise a means of supporting the first floor columns during demolition and construction. Thus, the team at BPE designed a system of steel supports that would rest on the wall directly below the portico columns. Before this support system could be constructed, it was necessary to ensure that the wall construction was substantial enough to support the weight of so much steel and limestone. The wall in question is hidden by the mass of stairs on the front of the house, and by stucco on the interior of the house in the basement. Thus, determining the condition of the wall required a gentle means of gaining access.

View of the core beneath the portico. | Credit: Drayton Hall Preservation Trust
Three inch diameter core hole in north side of basement wall. | Credit: Drayton Hall Preservation Trust

It was decided that a three inch core through the wall would be sufficient to assess its condition. If the inner wythes  (a continuous vertical section of masonry one unit in thickness) of brick were nothing more than rubble fill—everyone’s chief concern—this method would be a simple way to establish that. An area of failing stucco was identified low on the wall as an appropriate location to make the core. The stucco was removed from the face of one stretcher brick which was then removed, revealing the next wythe of brick in the wall. It was here that the core drill was used to create the opening in the wall. The core extended 16 inches through solid brick masonry before finally terminating in a void below the stairs on the front of the house.

For the purpose of establishing the condition of the wall on which we intended to support the columns, finding solidly laid brick along the full length of the core was the best possible outcome, but within minutes, what we found on the other side of the wall had drawn the rapt attention of everyone involved.

The nature of the space below the portico stairs has always been a mystery. It was thought that the space may contain rubble fill as is the case below the stairs on the opposite side of the house, but no one knew for sure. When the core drill punched through the brick wall into open space, everyone’s curiosity was piqued. What was on the other side of that wall? If we could find a way to get a camera in there, what might we see?

Craig Bennett inserting the camera into the space beneath the portico. | Credit: Drayton Hall Preservation Trust
Engineer Craig Bennett inserts a camera into the wall through the three inch core.| Credit: Drayton Hall Preservation Trust

We had a lighted wall scope at our disposal, but it was of little use as it did not provide enough light to illuminate the large open space. Enter Craig Bennett and his camera on a stick. Bennett has modified a 1x2 so that a small point and shoot camera can be attached for insertion into small spaces. The first images we were able to get from the void below the stairs were made by using the timer setting on his camera and taking a series of still shots with the camera rotated at various angles.

These images were fascinating, but somewhat difficult to make sense of. It was clear that we were looking at a large open space. We could see a vaulted ceiling, as well as brick rubble on the ground. One portion of the brick rubble was of particular interest as it appeared to have a curve on one side. At first, we wondered if we were looking at a curtail step from the base of an earlier stair. Speculation about what we were seeing became the focus of many conversations across the site, but without better images no one could say for sure what exactly we had discovered.

In order to capture higher-quality images, a construction light was produced and fed through the hole into the cavity below the stairs. This allowed Bennett to capture video on his camera. He adjusted his settings and fed the wooden pole/camera contraption back through the core. He took his time rotating the pole so that the camera could pan slowly around from ground to ceiling and back again. When he slid the camera back out, everyone huddled around the tiny screen once again. What we saw astounded and perplexed us.

Immediately adjacent to the hole made by the core drill, the video captured a brick pilaster engaged into the wall below the portico column. What’s more, the bricks are nicely laid, possibly rubbed and gauged and bear a striking resemblance to the exposed brick pillars beneath the outermost limestone columns. The pilaster that showed up on the video is directly in line with these pillars to which it bears such a resemblance. Further inspection of this wall also revealed very finely made mortar joints, a surprising discovery that was soon to be trumped by mortar joints exposed in another location on the wall.

The interior of the space beneath the portico steps. | Credit: Drayton Hall Preservation Trust
One of four newly discovered vaulted cavities below portico stairs. Bright white mortar shows location of the bricked-in passageway. | Credit: Bennett Preservation Engineering

As the camera continued to pan upwards, a section of incongruous brick and mortar became visible. It only takes a second to recognize a window-sized opening that has been bricked in. This “window” would have opened onto the passage way that leads from the basement out onto the lawn in front of the portico. Recently, I spent several hours studying this footage with Edward Chappell, Director of Architectural and Archaeological Research at the Colonial Williamsburg Foundation. Together, we were able to determine that this was not so much a window as a crude passageway, presumably to allow masons to scurry in and out of the vaulted space as they constructed the stairs. At first we thought that they would have bricked in this opening from the passageway, but upon careful inspection of some of the stills it became clear to us that the bricks were laid up from inside the vault. In fact, if you zoom in you can see trowel marks left in the mortar when the masons effectively bricked themselves into the vault. So, how did they escape? Presumably, the vault overhead had yet to be finished. So, the masons likely climbed out the top of the stairs before laying the bricks at the top of the vault.

More evidence regarding the construction sequence is revealed as the camera continues to pan upward toward the top of the vault. A few courses above the bricked-in window you see pockets in the brick, all in a horizontal line just below the spring of the vault. An identical line of pockets appear on the opposite wall as well. Clearly, these pockets were intended to hold a wooden support structure, but for what purpose? Here is where the brick rubble on the ground begins to make sense.

A piece of the three inch core cut from the brick wall. | Credit: Drayton Hall Preservation Trust
Interior face of brick core taken from south side of basement wall showing decorative grapevine joint. | Credit: Drayton Hall Preservation Trust

An identical core was cut through the brick in the same wall on the south side of the basement doorway. Again, we found a mass of brick rubble on the ground, but these bricks were in better condition than those we found in the first vaulted space, offering better insight into what we were seeing in the video. The brick on the south side of the doorway make a perfect half circle, the bottom of which is the same width as the vault. After seeing this, it became clear that this was brick centering, built upon wooden joists to support the vault above during construction. Presumably, the wood eventually rotted as none of it can be seen in any of the videos, and the brick centering above crashed to the ground.

The final exciting discovery below the portico stairs came not from a camera inserted through a hole in the wall, but from the brick core removed from it. The brick core on the south side of the doorway came out in three pieces. The third piece, a three inch diameter cylinder of brick and mortar from the inner face of the wall offered one of the most interesting and perplexing discoveries yet. I mentioned earlier that the mortar joints were finely made on this interior wall, but this core revealed that a decorative grapevine joint was used to point the interior face of the wall—a space that, as far as we know, has not seen the light of day since it was constructed in the 18th century. So why, then, bother to use such a decorative joint? In other parts of the house where we’ve exposed brickwork that was intended to be hidden, the pointing is as plainly utilitarian as you would expect. There are no decorative flourishes in the pointing in any other once-hidden locations around the house. So, what might this tell us about the portico stairs?

In order to capture video and images of the area beneath the stairs, the small camera had to travel through this three-inch core in the wall. | Credit: Drayton Hall Preservation Trust
Close-up image of core hole in basement wall.| Credit: Drayton Hall Preservation Trust

There has always been speculation that they may not be the original stairs to grace the front of Drayton Hall. The brickwork is not toothed into the main house, and some have pointed out that the brickwork seems more akin to that which was done following the American Revolution. Might the wall below the portico columns, now hidden by these stairs, have once been on full display? Perhaps, but the earliest known image of Drayton Hall, a 1765 watercolor by Pierre Eugene du Simitiere, shows the stairs that survive today. So, if there was a different stair configuration that exposed the decorative finishes of this wall, it was short-lived.

In addition to the fulfillment of thoughtfully rehabilitating Drayton Hall’s iconic portico, this project has been a boon to our efforts to better understanding how the earliest and finest example of Palladian architecture in North America came to be built. Numerous discoveries and additional avenues for research have been generated during this process, and while the rehabilitation work is on track to be completed by the end of this year, the attendant discoveries will likely unfold for years to come.

Trish Smith is curator of historic architectural resources at Drayton Hall, a site of the National Trust for Historic Preservation located in Charleston, South Carolina. She holds a master of science in historic preservation from the Clemson University & College of Charleston joint graduate program in historic preservation. The video is courtesy of Bennett Preservation Engineering. 

#Architecture #DraytonHall #HistoricSites

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