This document summarizes several architectural projects completed by Helen Johnson. It includes investigations of General Knox's Quarters in Valley Forge involving photographic documentation and analysis to determine construction stages. Another project analyzed the unstable cryptoporticus at the Woodlands Historic Mansion in Philadelphia through a conditions assessment and hypothesis about structural issues. A third project involved an interior assessment, restoration proposal, and re-use plan for the English Garden House at Mount Edgcumbe House and Country Park in Cornwall, UK.

1. Sample of Completed Projects
Helen Johnson
Salve Regina University, B.A. CHP 2007
University of Pennsylvania, M.S. HSPV 2010

2. Project: Architectural Investigation and Documentation of General Knox’s
Quarters, Valley Forge, PA.
A team of University of Pennsylvania Historic Preservation graduate students used photographic documentation,
measured drawings, plaster and paint analysis, archival research, and architectural archaeology investigations to
determine the construction stages of General Knox’s Quarters. This excerpt details the investigations and
conclusions concerning the East/West and North/South partitions of the second floor hallway. The hall closet
on the second floor is also explored and though a construction date for the closet was not determined, evidence
provided by the closet’s construction methods assisted in dating other features of the building.

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The measured
drawing of the door
to the left was part
of a documentation
of individual doors
found discarded in
a second floor room
of the house. The
styles and hardware of
the doors varied and
almost every stage of
the house’s occupation
was represented by a
door.
This door drawn in AutoCAD belongs to a hall closet on the
second floor of Knox’s Quarters. The time period of the
closet remains unknown however evidence of original base-
board indicates the closet was not original to the house.
This profile of the original chair
rail and baseboard from Knox’s
Quarters is drawn at 1/8”=1”
scale.
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4. Project: Analysis of Unstable Cryptoporticus at the Woodlands
Historic Mansion, Philadelphia, PA.
The Woodlands site consists of an early 18th century historic mansion and its grounds. The mansion’s front
terrace and cryptoporticus below the terrace were the focus of an investigation completed by myself and a
classmate. The investigation consisted of a thorough conditions assessment, a list of possible causitive
pathologies for these conditions, a hypothesis stating what is causing the severe efflorescence and structural
instability of the cryptoporticus, a proposed diagnostic methodology for validaing the hypothesis, and finally an
intervention and implementation plan.

5. The Woodlands Estate is located in Philadelphia, Pennsylvania, immediately west of the University of
Pennsylvania campus. The estate is comprised of the historic country house and the surrounding parkland acreage
that was later developed into a cemetery of the rurallandscaped type. Prior to this land-use, the estate served as
the home for various members of the Hamilton family. The last Hamilton heir of the property was William
Hamilton. After his death in the mid-nineteenth century the property was sold off piecemeal by family members.
Eventually the remaining, reduced lot was purchased by the Woodlands Cemetery Company of Philadelphia and
the company remains the owner today. The Woodlands mansion is one of the earliest and leading examples of
Adamesque architecture in the United States. As an icon of American architecture, the house has been placed on
the list of National Historic Landmarks, the Philadelphia Register of Historic Places, and the National Register of
Historic Places. It was documented by the Historic American Building Survey (HABS) in 1940 and again in 2003.
The house has many distinct architectural features including a brick-vaulted subterranean circulation passage
walled in brick and fieldstone called a cryptoporticus. The cryptoporticus is located on the north side of the house
supporting the north terrace from below. A number of deteriorating conditions are present throughout the house
due to a long history of neglect and current funding shortfalls, but the cryptoporticus is in an alarmingly
deteriorated state. This report focuses on the conditions of the cryptoporticus and the terrace it supports.
A thorough mapping and analysis of both the terrace and the cryptoporticus led to the identification of the most
serious condition which was widespread evidence of dislocation and displacement of structural elements of both
the terrace and the cryptoporticus, with the imminent possibility of serious structural failure across the entire
assembly.
After thorough examination of the possible causes for this structural displacement it was decided that the
displacement of both features is interrelated. The common factor between the two features is the silty clay soil
between the terrace and the top of the cryptoporticus ceiling. As a result it is hypothesized that these conditions
and their underlying mechanisms fundamentally relate to the moisture retention of the silty-clayey “intermediate”
soil placed upon the cryptoporticus vault as a foundation for the north terrace surface. The moisture-retentive
nature of the soil allows the mechanisms of frost heave and freeze-thaw cycles to displace structural elements,
opening new cavities that further exacerbate these cycles.
In order for this hypothesis to be correct there are several necessary and sufficient factors that must be present.
These factors are: soil moisture; threshold fluctuations in soil temperature, air temperature and humidity;
volumetric soil change; and threshold porosity of the brick in the cryptoporticus vault. Testing for moisture
content level of soil, temperature change of soil, temperature and relative humidity of cryptoporticus, potential
volume change of soil, and porosity of the cryptoporticus brick over the course of one year will prove or disprove
the existence of the necessary and sufficient factors. Once the data has been collected over the course of the
year, subsequent analysis will prove or disprove of the hypothesis.
Should the hypothesis be correct, steps must be taken to significantly ameliorate or effectively negate the dynamic
structural displacement before the cryptoporticus and terrace completely fail structurally. A guiding philosophy and
set of objective criteria provide a framework for evaluating multiple intervention opportunities. The philosophy
includes the historic importance of the features which must be retained and takes in to consideration current
circumstances and planned future use of the terrace and cryptoporticus. After considering these guidelines as well
as the data analysis of the test results, the following solution is proposed (should the data bear out the
hypothesis): a new, lightweight and historically appropriate surfacing assembly for the terrace that addresses
drainage and freeze-thaw concerns is installed on the north terrace and the marble copings are restored or
replaced in-kind on the new structure and repaired retaining wall. Below, the cryptoporticus vaulting is supported,
repaired, and protected so that it may serve as original fabric in an important interpretive element at the estate
for some time to come.

6. Project: Interior Conditions Assessment, Restoration, and Re Use
Proposal, Mount Edgcumbe House and Country Park, Cornwall, UK,
A team of University of Pennsylvania Historic Preservation graduate students collaborated with the University of
Plymouth’s Faculty of Arts, School of Architecture and Design and the Mount Edgcumbe House and Country
Park staff in the summers of 2007, 2008, and 2009. This particular project was the final step in the
exploration of the English Garden House located on the expansive grounds of Mount Edgcumbe. A thorough
conditions assessment of each room of the house revealed the cosmetic and structural repairs that would be
necessary before the house could be used again. The team also created a new use plan for the house based
on the estate mangement’s desire to use the structure as a tourist attraction and if possible a viable source of
income.

7. The floor plan of English Garden House was drawn by all three members of the 2009 English
Garden House team.

8. The West elevation of the bathing room was perhaps the most interesting. A niche was carved
into the wall to house the bronze dolphin faucet. When the faucet was attached to a water system,
water would pour from the dolphin’s mouths into the room’s enormous marble tub.

11. North elevation: Little to no repointing needed. Cleaning of
brick face necessary. Cause of efflorescence on brick facing
should be investigated and remidiated,
Fig. 1
Fig. 2
Project: Repointing Survey of All Elevations of the Newport Opera
House, Newport, RI.
Repointing cost estimates are highly circumstantial. The cost estimate is based on several factors
including composition of the mortar, the size of the joints between bricks, and the amount of mortar loss
and damage throughout the surveyed area. It should also include repainting of woodwork after the
repointing is complete such as cornices and window casings. Based on a ground survey of all four
elevations of the Newport Opera House the North elevation does not need any substantial repointing,
the East Elevation needs approximately 25% of its elevation repointed, the South Elevation needs
approximately 50% of its elevation repointed, and the West elevation needs approximately 75% of its
elevation repointed.

12. East Elevation: Repointing needed for about 25% of this elevation. Biggest concern is at
the southeast end of the building where mortar is completely gone and brick is missing.
(as seen in Fig. 5) Removal of plant life is necessary for the health of the building
envelope. Removal of graffiti also needed.
Fig. 3 Fig. 4
Fig. 5 Fig. 6

13. Fig. 7
Fig. 8
Fig. 9
South Elevation: Repoiting needed for about 50% of this elevation. Effloresence is a
problem on this elevation as well. Removal of plant life is necessary for the health of the
building envelope. Joinery at the foundation is a concern (see Fig 9).