Denfeld Senior High School – Historic Clock Tower Reroofing, Spire Replacement, and Masonry Restoration

Title: Denfeld Senior High School – Historic Clock Tower Reroofing, Spire Replacement, and Masonry Restoration

Award Category: Building Enclosure

Project Address/Location

401 North 44th Avenue West

Duluth, Minnesota 55807
United States

Submitted By: Chuck Schuh

Company Info

Inspec, Inc. Engineers/Architects

5801 Duluth Street

Golden Valley, Minnesota 55422
United States

651-238-8959

[email protected]

Project Description and Background: Project Description and Background (195 words – 300 Max.) The Denfeld Senior High School located in Duluth; Minnesota is an iconic ornate masonry structure of immense local importance built in the early 1900’s. Its most notable feature is the 100-foot-high functioning clock tower with a 26-foot-high spire on top of the tower roof. The tower exterior masonry, spire, and tower roof had experienced extensive degradation over the years. The school district made it clear at the beginning of the project that the community considered this project long overdue, and that the final remedial solution must be of high quality and longevity and must enhance the tower appearance while respecting its historical character. Inspec was chosen by the school district because of our extensive experience with complicated building envelope remediation. Inspec was hired to investigate and determine the reasons behind the extensive wall, roof, and spire degradation, and to design the appropriate remedial response that would prevent the same degradation from occurring for the remaining life of the school. The remedial design had to respect the existing historical character of the tower/spire and construction activities could not interfere in any way with normal student or administration activities.

Scope: Scope (439 words – 500 Max.) As the envelope expert, Inspec had the prime contract with the school district. Inspec’s consultants included the following firms: BKBM, Inc. – Spire Structural Engineering LHB, Inc. – Interior roof drain plumbing Infinity Scaffolding, Inc. – Swing Stage custom design Since the accuracy of the 100-year-old existing drawings were in question, Inspec verified existing conditions with extensive destructive inspection openings, which also helped to determine the cause for many of the deficiencies. The construction sequencing was a critical consideration since construction of some components relied on the completion of other construction activities. For example, since the lower roofs at the base of the tower could not support the masonry repair scaffolding needed, and since manlifts could not reach all tower elevations, a customized temporary swing stage with new tie-back davits had to be designed and installed on the roof. However, since the existing roof was failing, a new secondary roof had to be installed prior to the installation of the swing stage. Once all masonry repairs were complete, the swing stage could be removed, and the primary roof could be installed over the secondary roof. Since the construction schedule did not allow for all activities to be sequential, the fabrication of the spire had to take place at a remote site during the masonry repairs and then craned onto the roof after the swing stage was removed and the new primary roofing was installed. The project scope included the following work items (No order): • Extensive exterior masonry restoration at all four elevations of the iconic 100-foot-tall clock tower. This required A custom designed swing stage and new structurally designed tie-back davits for the swing stage. In addition, the existing tower roof parapets had to be reinforced with roof side bracing, so the exterior appearance was not altered in any way. • Both secondary and primary re-roofing of the tower roof was necessary in order to facilitate construction sequencing. • The existing spire was demolished, a new 26-foot-high spire was fabricated at a remote site, and then craned to the top of the 100-foot-high clock tower roof. A bird / batt prevention netting was custom designed and installed under the spire in order to prevent nesting. • New interior primary and secondary roof drains were installed under the new spire, • A new access hatch had to be installed through the roof without compromising the existing roof deck reinforcing. • A new stand-off platform had to be installed under the new roof hatch at the top of an existing 60-foot wall mounted ships ladder. • A new fall arrest line and harness was installed to be used in conjunction with the existing 60-foot ladder.

Solution: Solution (295 words – 500 Max.) Inspec discovered that the masonry walls were degrading because the existing spire was directing drain water against the inside face of the parapet and also through existing parapet scuppers. (See attached Existing Spire/Roof Condition sketch) The water then entered the head and bed joints of the masonry parapet and migrated down into the wall system. Also, since the spire was leaking and there were no drainage provisions under the spire, the existing roofing degraded prematurely and the high humidity under the non-ventilated spire promoted rot of the wood framing. In addition, access to the exterior side and to the underside of the spire was extremely difficult making routine wall, spire and roof maintenance infrequent. Inspec’s remedial design called for complete masonry restoration and a new galvanized steel framed spire with standing seam metal panels which terminated above new the roof. (See attached New Spire/Roof Design sketch) This allowed water to shed down directly onto the new roof which sloped to new interior primary and secondary roof drains under the spire. By terminating the metal panels above the roof, a new access hatch through the roof and corresponding stand-off platform underneath could be installed, thereby greatly improving roof access which facilitated future routine maintenance. The standing seams and custom color-coating of the spire metal panels successfully mimicked the original aesthetics of the old spire. The chance of bat and bird damage which was present under the old spire was eliminated with a custom designed bird/bat prevention netting. All existing parapet metal bracing was replaced and completely enclosed and flashed, so that the previous corrosion would not be repeated. During fabrication of the spire, value engineering was suggested by the fabricator which improved the design while not Adding cost to the spire.

Value: Value ( 92 words – 500 Max) As the prime architect and envelope expert Inspec’s exterior envelope investigation and assessment experience enabled us to identify the cause(s) of the problem issues and to develop the appropriate long term remedial design response. The many RCI and IIBEC articles, continuing education classes, and conventions over the last 15 years has contributed greatly to the expertise of the Inspec team. The RCI’s and IIBEC’s dedication to detail, performance and ethics has inspired Inspec to adopt a philosophy of long term performance and putting the Client first.

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