140P2021R0055-0004_Att05-FinalPDReport-RoofAndAssociatedFeatures_200414redacted_0004.pdf

9GWWO, Inc./Architects

EXISTING CONDITIONS OVERVIEW

Roof and Associated Roof Features

Architectural

Information supporting this report is based on Rehabilitation and Restoration Drawings dated May 1964, field observations on November 20, 2019, laser scanning, and drone photogrammetry completed on November 26, 2019.

The current copper roof was installed in 1964. The roof consist of 1 ¼” folded standing seam copper panels, nominally 4’-4” width. The roof panels are installed over 5/8” wood sheathing that covers the existing wood board sheathing. The design team suspects wood board sheathing was also installed in 1964. This sheathing is visible from below in the attic space and appears consistent throughout the roof. The roof pitch is 3 over 12. The copper roofing is flashed into a sky-facing reglet joint in the marble cornices at the eaves and rake edges (images 19 & 20). The sealant in many locations has voids which appear to channel and trap water and has most likely caused the stone to crack during freeze thaw cycles, see (Image 21). The copper panels join at the ridge with a single standing seam joint that transitions to a flat joint for a short distance(Image 38).

The flat joints extend approximately 3 – 5-inches before transitioning to a standing seam joint (Image 22).

The pole gutter is made up of wood 2 x 4s anchored to the roof with bronze 3” x 2” x 1/8” angles. The angles are connected at 32” O.C. and anchored into the wood 2 x 4s and wood sheathing (Image 23). On the downside of the pole gutter, the copper roofing is flat seamed with soldered joints. All the gutters were clogged with leaf debris preventing water from draining. There are wrought iron down spout strainer/guards at each gutter (Image 24). The cornice stones show copper staining resulting from poor draining at clogged gutters (Image 25).

The flashing at the chimney and crickets does not appear to extend 8” above the roof surface in most locations. The flashing is attached to the stone chimney with a reglet joint that meets at a stone joint and is sealed. The counter flashing is riveted at the corners where the flashing turns around the north and south faces of the chimneys (Image 26). In some locations, these joints are open which may contribute to water intrusion at the chimneys (Image 27). The flashing Image 20 -Copper roofing joint in marble cornice at rake edge (GWWO, 2019).

Image 19 - Copper roofing joint in marble cornice at eave (GWWO, 2019).

10 GWWO, Inc./Architects

INDEPENDENCE NATIONAL HISTORICAL PARK

Image 24 - Wrought iron down spout strainer/guard (GWWO, 2019)

Image 25 - Copper staining on cornice stone (GWWO, 2019).

Image 22 - Joint at roof ridge (GWWO, 2019).

Image 21 - Void in sealant at eave edge (GWWO, 2019).

Image 26 -Flashing at cricket at chimney(GWWO, 2019).Image 23 - Debris collecting at pole gutter (GWWO, 2019).

11GWWO, Inc./Architects terminates with a reglet joint cut in the stone at an angle parallel to the roof slope at the north and south faces of the chimneys.

There are several flashed curbs at skylights and mechanical access hatches as well as flashing at round vent pipes (Image 22).

The design team removed debris from clogged downspouts and, through this process, observed leaking at the elbows where some of the downspouts bend to meet the water table (Image 28).

The roof is accessed via a roof ladder which leads to a steel framed, wire glass skylight/hatch at the north end of the bank, just west of the ridge. Access to this hatch requires climbing over HVAC equipment making it difficult for maintenance to the roof.

Additionally, the roof does not have safety tie-off points for maintenance personnel. The design team also recognizes that the current roof does not have a lightning protection system, which seems uncommon for the area, as neighboring properties where observed to have roof-mounted air terminals.

Conservation

The existing Second Bank roof, and associated roof features, are from the 1965 renovation, and are therefore not original to the building. No conservation considerations were noted in this on site investigation.

Structural

The existing gable roof consist of four bays of simply supported timber rafter framing spanning east/west.

Rafter dimensions vary slightly but are generally on the order of 3 1/2” wide by 9” to 10” deep. Spacing also varies but is generally on the order of 18” to 24” on center. Spanning east/west, rafters bear on multi-wythe exterior masonry bearing walls. Three interior north/south axes of bearing are present, with structural support at each axis as follows:

� At the north and south wings, rafters bear on continuous wood plates placed on interior multi-wythe brick masonry bearing walls.

� Above the central barrel vault and at the south mechanical room space, rafters are supported on a series of iron trussed wood girders which align with the interior multi-wythe brick masonry bearing walls.

� Above the north mechanical space, rafters were believed to have originally included a horizontal timber collar tie. However, more contemporary steel framework is present above the mechanical space to support both new MEP features and the existing original timber rafter roof framing above.

Based on existing documentation available, this steel framework is believed to have been installed as part of the 1972 interior restoration and rehabilitation effort.

� At the north and south porticos, rafters bear on timber purlins, which in turn bear on multi-wythe

Image 27 - Flashing at chimney corner (GWWO, 2019).

Image 28 - Downspout elbows at water table (GWWO, 2019).

12 GWWO, Inc./Architects masonry bearing wall construction

The team observed several past roof framing revisions, including contemporary wood framing installed to infill previous roof openings and full-depth wood blocking installed at midspan of existing original rafter framing.

Several more contemporary penetrations through the original wood framing were observed.

Surface water staining was noted at multiple locations but was most prevalent at the east and west façade bearing locations. Such staining is generally indicative of roof leakage, either past or present, and raises concern that decay may be present. Staining was generally observed at most locations where sloped roof framing intersected existing chimney stacks which extend upwards above the roof surface (Image 29).

Decayed rafter framing was also noted along the east façade, coinciding with an abandoned chimney location (Image 30). Along the underside of several rafters, notching was noted (Image 31) as well as a saw cut groove, observed along the underside of a rafter (Image 32). Such notching and saw cuts reduce the structural section capacity of the rafter, raising concern that the reduced rafter section may be structurally inadequate.

Two types of rafter cracking were observed, including material deficiencies (Image 33) and flexural cracking (Image 34). This indicates that the section capacity of the rafters in question may be reduced.

Contemporary MEP systems have been installed within the attic space, with much of this equipment supported along the underside of the roof rafters above the attic space (Image 35). Given the age of the building, the original roof framing was likely not sized to support contemporary MEP features, and it is not known if structural analysis of the existing roof framing was performed to determine if the existing rafters were sufficient to support the new loads associated with the MEP features. Considering current code-prescribed loading combinations for dead, live, snow, wind, and MEP loading cases, there is concern that the roof framing may be inadequate to support the current code-prescribed loading combinations.

Several roof openings were noted, including original roof openings, and openings created in subsequent years, by altering original framing. There was evidence of infilled abandoned openings. Wood header beams were observed that support cut rafters and are

Image 29 - Staining on rafter at where chimney stack intersects roof framing (SGH, 2019).

Image 30 - Decayed rafter framing along east façade (SGH, 2019).

Image 31 - Noched rafter (SGH, 2019).

13GWWO, Inc./Architects

Image 35 - Contemporary piping system supported from original roof rafters (SGH, 2019).

Image 32 - Saw cut groove, observed along the underside of a rafter

(SGH, 2019).

Image 36 - Original single-ply roof rafter, currently serving as trimmer, supporting additional point loads from multiple headers framing around adjacent openings (SGH, 2019).

Image 33 - Rafter cracking as a result of material deficiencies (SGH, 2019).

Image 37 - Sagging along the ridge of the roof, above north attic mechanical space (SGH, 2019).Image 34 - Flexural cracking (SGH, 2019).

14 GWWO, Inc./Architects supported by existing rafters serving as trimmer beams.

At several locations, the trimmer beams consist of only a single ply (Image 36). This raises structural concern, as the trimmer beam in question is supporting additional point loads from the header beams.

Two notable sags were identified along the ridge of the gable roof, with sags loosely corresponding to both the north (Image 37) and south (Image 38) attic mechanical spaces below. The sagging ridge line raises concern that the structural framing coinciding with the ridge sag may be damaged. At the south end of the north mechanical space, support of the rafters along the ridge transitions from an interior brick masonry bearing wall to the contemporary steel framework. However, the steel framework was noted to stop several feet short of the brick bearing wall, with several roof rafters bearing on neither the contemporary steel framework nor the interior bearing wall (Image 39). A structural analysis of this zone is necessary to determine if the existing horizontal collar ties are sufficient to support the code-prescribed loading combinations.

The site visit uncovered the need for two new roof features to support serviceability and life safety benchmarks:

� New fall arrest anchors: to be utilized as tie off points for life safety lines protecting workers while utilizing conventional swing stage access or to support a single worker utilizing a boson’s chair for access to a façade for window washing and limited maintenance

� New roof hatch opening: to provide means to remove / install mechanical equipment within the attic space.

Image 39 - Contemporary steel framework spanning shy of masonry bearing wall (SGH, 2019).

Image 38 - Sagging along the ridge of the roof, above south attic mechanical space (SGH, 2019).