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Home My WebLink About2.C. City Hall Roof Replacement ROSF_�OC. NT EXECUTIVE SUMMARY CITY COUNCIL City Council Work Session: April 8, 2014 AGENDA ITEM: City Hall Roof Replacement AGENDA SEC ION: PREPARED BY: Andrew J. Brotzler, PE, Director of ' . blic Works / City Engineer ; AGENDA NO. 2C ATTACHMENTS: Information from CNH Architects APPROVED BY: RECOMMENDED ACTION: Discussion BACKGROUND On August 6, 2013 the City Hall roof sustained significant hail damage during a severe storm that passed through the south metro area. Since the estimated cost to replace the roof will exceed$100,000, the City is required to advertise and solicit sealed bids for the project. The city has attained the professional services of CNH Architects to prepare bid documents for the project and to perform the construction administration. City staff has met with architects from CNH on two occasions to review the existing roof conditions and discuss replacement options. Due to the existing roof design and pitch, the sole option for replacement on the roof is with in-kind standing seam metal. Consideration of any other roofing materials would require structural modifications to the roof that would not be covered under the insurance claim. The recommendation from CNH is to replace the roof with a similar standing seam metal roof,improve the drainage with a new gutter system, and replace all damaged fascia. The insurance adjuster from the League of MN Cities is aware of and in agreement with the plans for roof replacement. Quinn Hutson from CNH Architects will be available at the Work Session to discuss design options and answer questions. SUMMARY Staff is requesting input from the City Council regarding color for the replacement roof. G•1Public Works\Storm Damage12013,August 6\20140408 CWS City Hall Roof Replacement.docx CITY OF ROSEMOUNT - CITY HALL REROOFING UPDATE April 1, 2014 Introduction The existing metal standing-seam roof system on the Rosemount City Hall was damaged by hail in August, 2013, and is in need of replacement. The review of the roof system by the City's insurance carrier has determined that the majority of the roof received this damage and has indicated that the entire metal roof system including metal facias will be covered by the insurance policy. CNH Architects has been retained by the City of Rosemount to analyze the reroofing options, develop recommendations for the City, and then provide designs for re-roofing City Hall. The following update prepared by CNH Architects outlines the current project approach, research results to date, system recommendations, and provides some aesthetic options for consideration by the Rosemount City Council. Index Background 2 Project Goals 3 Research Update 3 Aesthetic Options 5 CNH Architects, Inc Page I I 4:27 lairett Background The current City Hall standing-seam metal roof dates to the original building built in 1986 as well as to the 2001 expansion of the north side upper level roof. Both original and new roofs are a white standing-seam roof system of similar styles. There is also an existing ballasted EPDM (rubber) roof that was built as part of the 2001 expansion. This rubber roof was not damaged by the hail storm. The existing metal roofs likely had a 20 year warranty, which was typical for the periods these were installed. This results in the original roof being out of warranty and the 2001 expansion roof being 13 years into its warranty. The existing standing seam roof system is installed on multiple areas on the City Hall. This system covers the sloped roofs and extends down to create large facias at both the gable and eave ends of the sloped roofs as shown in the photo of the existing building below. X19"ally aax ft 'aie" City Hall—East Entrance ktik3w City Hall—West Elevation CNH Architects. Inc Page 12 1 ('11/11(�5. • Project Goals The primary project goal is to replace the damaged standing seam roof; however, several other goals have been identified by the city. These goals being evaluated include the following: 1. Evaluate reroofing material options for City review. 2. Evaluate elimination of internal roof gutter system over entry areas. 3. Replace and upgrade gutter and downspout system improving durability, effectiveness and better direct downspout drainage. 4. Evaluate and reduce ice dam and icicle development potential. 5. Evaluate areas of excessive heat loss through the roof and address cause(s). 6. Evaluate roof color options, presenting renderings of City Hall with each color option for City Council review and final selection. Research Update CNH Architects has begun the study of the reroofing goals with a summary of the current updates provided below. The first review item is the reroofing material options. The existing standing-seam roof covers the majority of city hall with a shallow slope (1% : 12) on the east and moderate slope (3% : 12) on the west. The metal roofing system also covers large facias on both the eave and gable edges. The shallow 1 '/2 : 12 slope becomes the limiting factor on roofing replacement material options as indicated in the chart on the next page. CNH Architects, Inc Page I 3 Roofing Material Comparison Chart Roofing Material Image Minimum Warranty Comments Slope (Years) Standing-seam metal =_ ,,.\\ 1:12 Up to 25 Special installation . I \4 '\ requirements for slopes < 3:12 Metal shingle panel 3:12 20 + Horizontal panel sizes vary, no (horizontal) option for slopes under 3:12 Concrete tile --"11111114. ., 4:12 Lifetime Some warranty limitations apply, high weight often requires reinforcing of existing roof structures Synthetic shake/tile `' / , ` 1 2:12 Up to 50 Select styles only most require 4:12 minimum slope Wood shingle/shake ' " .. 4:12 20 to 25 Higher warranties are limited Asphalt shingle 2:12 / Up to 35 Low slope with special '':' -4 4:12 underlayment, otherwise minimum 4:12 Single-ply membrane 1/8:12 Up to 25 Not meant for aesthetically (EPDM or TPO) visible roofs or facias Rolled asphaltic roofing ""11.1 1/4:12 Up to 20 Not meant for aesthetically visible roofs or facias CNH Architects, Inc Page 1 4 agcHn1E( Of the roofing systems indicated, only the metal standing-seam systems provide an appropriate aesthetic image and are designed for the lower slope of the east side of the City Hall roof. Standing-seam roof systems are now available in lengths sufficient to eliminate all joints within the vertical run of the existing roof, unlike the current installation, providing reduced risk of moisture intrusion at lap joints. In addition, CNH Architects recommends using a mechanically double-locked standing-seam design for the entire roof system instead of the mixed double-lock and snap-on cover approach currently installed. The internal roof gutters over the east and west entry areas are typically a high maintenance item as has been shown by past repairs mentioned by city staff. These areas tend to be damaged by ice expansion within the gutter and then allow water to intrude into the structure itself. It is our recommendation to infill these openings within the roof and replace them with eave gutters like the rest of the facility. The existing eave gutters will be replaced as part of the standing-seam roof replacement. The replacement eave gutters will all be sized to meet the flow rate for a typical rain event, many of which will be larger than some of the current residentially sized gutters. The new downspouts will be positioned to allow for appropriate gutter slopes and considering drainage routes away from the building at grade. The is also the potential to connect downspouts to below ground stormwater piping in the future. The next two items to be evaluated are ice dam / icicle formation reduction and any potential areas of excessive thermal transfer through the roof. A thermal imaging test will be scheduled to determine the thermal transfer conditions of the building. This test will indicate areas where there are gaps in insulation, thermal bridging, or poor ventilation all of which can lead to ice dam / icicle formation and energy inefficiencies. Once the results are available, CNH Architects will evaluate methods to reduce these issues and will present these results and recommendations to the City. Aesthetic Options Since the entire standing-seam metal roof, facias, gutters, downspouts, and associated trim will be replaced, this provides the opportunity to evaluate the potential aesthetic impacts of replacing with different colors of prefinished metal. The images on the following pages show computer renderings of City Hall from the east and from the west. The renderings have been created with five different roof color options selected by CNH Architects and city staff for consideration. These colors include the current white, medium and dark bronze tones, and two different green options. None of the colors shown have a measurable physical benefit; consequently the selection is an aesthetic preference only. However since the standing-seam metal roof and facias are a significant part of the City Hall design, the changes in metal colors likewise have a very noticeable impact on the resulting image. CNI-I Architects, Inc Page 15 42Z Oft 4 ',I l ' "° '"°'11°0 ! r - 1.1.1t111 Tir it -if ir lair. I -...,............,=L-----my -- � ' t � 1. t_ ,. ,r. CNH Rosemount City Hall Roof Replacement - Existing Option Stone White Aec„0rf ris i i I iX� -.11111116,11111111Lia-a- ii Qy _.LI,OM 17a 111U14IH. .. 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