Attachment_9__Old_North_Crypt_Conditions_Survey.pdf

July 2017

BUILD ING CONSERVAT ION ASSOC IATES INC

Old North Church: Crypt

Boston, MA

Conditions Survey

BUILD ING CONSERVAT ION ASSOC IATES INC

Old North Church: Crypt

Boston, MA

Conditions Survey

Prepared For

Old North Church and Foundation

Prepared By

Building Conservation Associates, Inc.

10 Langley Road, Suite 202

Newton Centre, MA 02459

BCA Team

Lisa Howe

Araba Prah

Old North Church Crypt Page 1 Page 1 Condition Survey

July 2017

BUILD ING CONSERVAT ION ASSOC IATES INC

INTRODUCTION

Building Conservation Associated (BCA) performed an interior survey of the Old North Church Crypt located at 193 Salem Street in Boston, Massachusetts, on July 06, 2017. The survey consisted of a visual assessment of the brick walls accessible from the walkway. The team noted conditions on photo-montaged elevations of the crypt provided by the architect. Areas behind oil tanks, mechanical pipes, and cabinets in addition to inside the tombs were not visible to survey.

This report summarizes the findings of BCA’s survey and provides minimal intervention recommendations for the treatment of the conditions found in the crypt

DESCRIPTION OF BUILDING

Located in the cellar of Old North Church (also known as Christ Church of Boston), the burial crypt is made up of 37 tombs built between 1732 and 1860. There are three entrances that lead into the cellar- one off of the columbarium, one from the Bigelow Courtyard, and another from the Lantern Garden. The entrance from the Bigelow Courtyard was historically how the crypt was entered.1 Currently, the crypt is open for guided tours for historical heritage and interpretation purposes. One of the tombs (Tomb 24) has been opened and cleared to allow visitors to see the interior.

The foundation walls of the cellar are comprised of rubble stone, and overall the space is rectangular in plan. The crypt is built of red brick, and the tombs are arranged in two areas:

against the stone walls (23 tombs) and within a central block (14 tombs). Between these two areas is the main circulation path, which is approximately 5 feet wide with a concrete floor.

Access to the tombs is from this this walkway.

The tombs are fairly uniform, built of straight solid brick walls with barrel-vaulted ceilings. There are slight differences in style due to the varying construction dates of the tombs. At one point the brick walls facing the pathway were whitewashed or painted white. This coating is currently in very poor condition and large areas of brick are exposed where the coating has failed.

Originally, access into each tomb was “provided through an arched entryway, all of which have been subsequently sealed. Several of these entrances appear to have been re-opened via a simple rectangular cut, only to be sealed again [with stucco] at a later date.”2 A 1912 inventory of the tombs indicated that some of the doors were made of wood, which have subsequently been removed and replaced with lath, metal mesh, and stucco which is visible today.3 Some openings, such as the Strangers Tomb (Tomb14) have been sealed with brick. Arched rectangular slate and metal tablets can also be found in the doorways of many tombs. Most of the slate doors have hand carved inscriptions. There is one contemporary plaque located on the far right of the south elevation “given to the church by the US Navy to pay homage to Captain Samuel Nicolson”.4

1 Jane Lyden Rousseau, Of the Lonely Belfry and the Dead: An Historical and Archaeological Study of the Burial Crypts of 2 Rousseau, 7.

3 Rousseau, 61.

4 Mark Hurwitz, "#11 – The Life and Times of Captain Sam Nicholson," The Old North Church, , accessed July 19, 2017, http://oldnorth.com/historic-site/11-the-life-and-times-of-captain-sam-nicholson/.

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The structural system of the crypt is comprised of traditional load-bearing masonry construction. The thick stone and brick walls support oak beams and girders that run north to south. Extending the length of the central block is a 22-inch wide brick wall, which acts as a midspan support for the above structure. 5, 6 The walls of the tombs also provide support for the horizontal members above. “In 1968 the crypt’s original structural support system was reinstated with the installation of a series of new brick masonry piers”.7 During this renovation the original pier footings were replaced with poured in placed concrete footings, in addition to a new concrete floor for the pathway.8

The crypt also houses the church’s mechanical and electrical system, with various generations of pipes and wires running adjacent to the tomb walls and above the pathway. Radiators located at ceiling height along the north and south elevations help to keep the space warm and dry. These installments were once used to heat the nave above, but currently only serve the cellar.9 Two large oil tanks are located in the southeast corner of the cellar; one in front of Tomb 1 and the other stationed between Tomb 19 and the double wood doors leading to Bigelow Courtyard (located on the far right of the east elevation).

5 Only the west and east facing ends of the wall were accessible for the survey.

6 Rousseau, 7.

7 Rousseau, 11.

8 Ibid.

9 Rousseau, 9.

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SUMMARY OF FINDINGS AND RECOMMENDATIONS

Overall the crypt walls are in fair condition. The most common issues found were deteriorating and missing bricks and open mortar joints. The brick deterioration was most likely caused by rising damp and the buildup of salts (efflorescence) within the walls over the past 285 years.

There have been many repointing campaigns over the years, and in many areas the mortar is much harder than what its typically prescribed for historic masonry. Other conditions noted were cracks and missing portions in areas with stucco, and a large crack in the rubble wall located on the far left of the east elevation near one of the entrances. It is recommended that a structural engineer evaluate this crack and section of wall for movement.

See the condition survey located in the appendix for complete findings and locations of conditions.

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Masonry

Brick

Condition:

Brick is the primary building and structural material of the crypt walls. Most of the brick (with the exception of the brick found in the piers) appears to be historic, originating from the mid- 18th century making them relatively soft. The bricks are red-orange in color and laid in the Common Bond pattern (also known as the American Bond). In various sections along the top of the walls bricks have been replaced or removed. Areas of missing brick could be due to a combination of the deterioration of the units or units being removed to install pipes and wires for the mechanical and electrical system. During the survey it was noted that a plastic sheet was covering the top of interior east-facing crypt wall (see 5. Interior East Elevation in appendix).

Under the sheet were a number of loose and deteriorated bricks.

Deteriorated brick are found in various locations along the walls and do not appear to follow a particular pattern. This deterioration may have been caused by continuous cycles of rising damp and efflorescence (or salts). Rising damp is a condition where water from the ground is drawn up into a wall made of a porous material, such as brick. Minerals and salts contained in the water are also drawn up into the wall, and can collect in the pores of the brick or transported onto the face of the wall, after the water evaporates. When salt crystals collect and grow within the masonry’s pores, they expand leading to cracks and crumbling of the soft brick material. This results in the partial or complete loss of individual brick found in the crypt. During the survey it was determined that approximately 192 bricks need to be replaced (see condition survey for locations). This number does not take into account areas at the top of the walls where units are missing.

At one point the crypt walls were painted white. This coating has severely deteriorated, but remnants still partially or completely cover bricks.

Recommendation:

To preserve the crypt it is highly recommended that the walls be gently cleaned to remove any loose coatings and debris. This can be performed using a dry natural or synthetic brush and vacuum to remove loose material. To remove more stubborn soiling, natural or synthetic brush and a small amount of warm water can be used to gently scrub the area. After cleaning the area, excess water should be removed using rag or towel. It is not recommended that metal bristle brushes, harsh abrasion methods, or strong chemicals be used to remove the painted areas. This may result in damage to the underlying brick.

In areas of deteriorated or missing bricks, it is recommended that they be replaced with units of the same shape, color, and hardness as surrounding units using a soft mortar mix (see Mortar section for specifications). Cavities with disintegrate brick will need to be cleaned out prior to installing replacement units

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Figure 1. Area of deteriorating bricks and open mortar joints found on the interior wall of Tomb 24

Figure 2. Section of wall with the white coating and cluster unsound bricks.

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Mortar

Condition:

The mortar found in the joints appears to be from various repointing campaigns, resulting in different mortar mixes and colors. These colors range from dark gray to a light buff. A detailed mortar analysis was not performed, but due to the hardness of some of the repointing mortar noted during the survey, it is likely that the hard mixes contain either white or gray Portland Cement. Because of the softness of historic brick, hard or high strength mortars should not be used. Mortar should be softer than the adjacent masonry, so it acts as a sacrificial material as the brick expands and contrasts. Also low vapor permeable mortars should not be used. The avoidance of low vapor permeable and high strength mortars will help to preserve the historic brick. In some areas it was noted that the mortar might be too hard for the adjacent masonry (such as the joint between the historic brick and slate doors). Areas of hard mortar have been recommended for removal and replacement with a soft mortar.

Recommendation:

Areas of missing and disintegrate mortar can be found on all elevations (see condition survey).

To ensure the continued integrity of the brick crypt walls and rubble walls, all areas that have open joints or disintegrate mortar should raked out and repointed using a soft mortar mix with a non-hydraulic lime to sand ratio of 1:3. The sand used in the mix should well graded and the color of the sand should match the adjacent area. Prior to repointing all the joints, a sample of the mix should be produced and allowed to fully cure to confirm the appropriate appearance.

Figure 3. Hard pointing mortar adjacent to historic brick.

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Figure 4. Hard mortar around slate door

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Slate

Condition:

There are 20 slate plaques and doors in the crypt, with inscriptions of the interred hand carved into the stone. Most of the slate tablets were in good condition and did not show signs of notable damage or deterioration. Of the tablets that had signs of damage, the conditions ranged from cracks to paint and cement splatter (see condition survey). Several of the riveted slate tablets/doors had been fitted with large iron hinges, latches, and padlocks.10 During the survey it was noted that many iron hinges have corroded, which could be contributing to the cracks found in the stone. It was also observed that the perimeter of many slate doors and plaques have been parged with a hard gray mortar. This can be contributing to the cracks found, and also lead to greater deterioration of the stone and surrounding brick in the future.

Recommendation:

It is recommended that all the slate doors and plaques be gently cleaned to remove paint and cement splatter. It is also recommended that areas around the tablets with hard mortar should be removed and replaced with a soft mortar. The mix should have a non-hydraulic lime to sand ratio of 1:3 (see condition survey for locations).

Figure 5. Slate door with repaired crack

10 Rousseau, 61.

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Figure 6. Crack in slate

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Concrete

Condition:

The concrete floor (located in the walkway) is not historic but from the renovation campaign in 1968. This slab was poured over the previous surface, which condition is unknown. As for the current floor it appears to be in good condition, and does not require significant intervention.

Recommendation:

It is recommended that the floor be swept regularly to prevent the built up of dirt and debris from the walls as visitors walk through the space.

Rubble Wall

Condition:

There are a few sections of the rubble stone foundation wall accessible from the perimeter walkway. Various items such as components of the mechanical system, an oil tank, or miscellaneous objects prevented a close inspection of some areas. Areas that could be assessed appeared to be in good condition with the exception of the rubble wall located on the far left of the east elevation adjacent to the entrance from the columbarium. Here, a large crack (approximately ¾”) has formed near the corner of the wall.

Recommendation:

It is recommended that a structural engineer evaluate the large crack for movement. Once it is determined to be sound, the joint should be repointed with soft mortar mix with a non-hydraulic lime to sand ratio of 1:3.

Figure 7. Large crack found in rubble wall on the east elevation near the entrance to the columbarium.

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Metal

Condition:

There are metal arched doors (believed to be steel) located at Tomb 3 (south elevation) and Tomb 19 (east elevation). Both doors appear to be in good condition and aside from general cleaning do not require any further intervention. There are a number of exposed ferrous hinges found on the slate arched doors and protruding from the stucco covered doorways. Many of these hinges have rusted causing rust staining and cracking to the surrounding material. Severely deteriorated steel strips were also found at the doorjambs of Tombs 8 and 9 underneath cracked and missing sections of mortar.

Recommendation:

It is recommended that the metal doors be gentle cleaned to remove any accumulated dust and debris. Concerning the rusted hinges and strips it is recommended that they be scraped to bare metal and coated with rust inhibiting paint. After the strips have been treated the area should be repointed using a non-hydraulic lime to sand ratio of 1:3.

Figure 8. Rusted ferrous latch mechanism for slate door.

Figure 9. Severely rusted ferrous strips under mortar in tomb doorjamb

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Stucco

Condition:

There are 18 sealed doorways that are covered with stucco. Many of these doorways show some degree of deterioration. Conditions noted were cracking, rust stains around exposed hinges, and loss of large areas of material exposing the underlying structure (such as metal mesh, wood strips, and wood doors).

Recommendation:

The condition at these locations should be discussed among the design team to determine the appropriate treatment recommendations. Treatments could range from stabilizing the materials in place to replacing all of the stucco openings to provide a more consistent approach.

Figure 9. Cracks in the stucco and a large area of loss exposing metal mesh backing, lath strips, and wood door of tomb

Appendix A

Old North Church Crypt Page A

*Areas marked in blue represent unsound or deteriorated brick units that will need to be replaced. Areas marked in red represent locations that will need to be repointed.

1. EAST ELEVATION

2A. SOUTH ELEVATION SECTION

2B. SOUTH ELEVATION SECTION

3. WEST ELEVATION

4A. NORTH ELEVATION

4B. NORTH ELEVATION

5. INTERIOR EAST ELEVATION

6A. INTERIOR SOUTH ELEVATION

6B. INTERIOR SOUTH ELEVATION

7. INTERIOR WEST ELEVATION

8A. INTERIOR NORTH ELEVATION

8B. INTERIOR NORTH ELEVATION

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