Hoffmann Architects

Journal of architectural technology published by Hoffmann Architects, specìalists in exterior rehabilitation

First lssue 1997 Volume l5 Number I

Copper Roofing: An Enduring Linl< Between Past and Future

with theìr standard 7}-year warranty, Arthur L. Sanders, AIA Certainly, not all buildings are intended to last more than 30 or 40 years and C rrtor-..ufted copper roofìng, rich may not warrant a copper roof But in detailing, rich in history, spealpatina a testament to the passage of time, But as a building matedal, Without a doubt, copper was and is a copper shouldn't be relegated to the high initial cost item, typically two or past, despite competition overthe past more times the cost of other roolng few decades from lower-cost, pre-formed types, with the exception of slate and metal roofìng systems and other roofìng tile This high initial cost was a primary types. lf longevity, low maintenance, reason why copper traditionally was and a frong aesthetic statement are a selected only for "important" buildings building owner's goals, copper remains - public facilities, churches, libraries, the hands-down favorite. and other buildings of long-term value to their owners and their communities, When properly designed, detailed, and That cost came from the high level of installed, a copper roof can easily last craftsmansh ip required for instal lation, 50 years or more with relatively little along with the cost of the material itself maintenance or care. And there is Today, modern tools and equipment ample evidence of copper roofs have helped reduce installation costs \ enduring for a century or longer and material waste, Even so, copper as befits the historic, cultural, and- civic installation is still essentially a "f eld job' value of the buildings they so often requiring great skill and craftsmanship grace. For example, the standing seam - and properly detailed design copper roof installed in the I B30s on documents, Philadelphia s Old Christ Church lasted unttl 1967, One remaining section of Overthe long haul, however, a well- the original copper roof on the First designed and correctly installed copper Bank of the United States (also in roof will more than pay for itself One lnstallation of a batten seam copper roof Philadelphia) is still in service today,202 reason forthat is copper's durability, on a New York City high-rise office years later. Stacl< that up against today's which makes it likely to last the life of building. pre-fabricated metal roofì ng systems, the building. Regular maintenance is easrly implemented, as long as design documents and construction have As Senior Architectw¡th Hoffmonn addressed the few special requirements Architects, Arthur L. Sandert A/A oyenees of copper, particularly in planning for mosonry, plozo, ond roofing rehobílitotion thermal expansion and contraction. Þrojects, rncluding mony of the fum's coÞPer rooftng rehobilitotion efforts. ln contraf, today's low-slope membrane

Copyright Hoffmann Architects I 997 Hoffmann Architects / Journal

roof or steep-slope shingle roof needs Deterioration the runoff from either of these metals regular maintenance, patchìng, and . Copper is susceptible to corrosion will eventually stain the copper darl<- repai¡ and usually requires full replace- from contacl with allsulfur dioxide) While the copper Coppers distinctive color and appear- patina provides some level of protec- Mechanical failure ance offer design atlributes unmatched tion from acidic moisture, copper roof . Failing to provide adequately for in other roofìng sylems, Whether in a valleys, gutters, and sllylight frames are copper's natural expansion and hìstoric setting or in newer structures, a particularly susceptible to its damaging contraction is the leading cause of copper roof is well wodh restoring or effects. That's because moisture tends mechanical breallead to following section looks at some of woods altogether, roof failure. For example, copper coppers specific problem areas and ways . lron and steel should not be placed sheets installed over cupped wood to avoid these durìng installation or repair. above copper, as the interaction of will eventually tear along the sharp, upturned edges of the sheathing, while the high points of a rough concrete surlace will telegraph through the copper and lead to pinpoint holes in the roof . Secondary causes ofcopper roof failure can include the use of inappro- priate materials, such as using steel nails to secure cleats, The galvanic interac- tion between the steel and the copper will eventually corrode the steel nail and undermine the structural integdty ofthe cleat,

Protecting other building materials Copper can hasten the deterioration of other metal buildìng materials through galvanic action, Galvanic action occurs when a vulnerable metal, such as aluminum, zinc, steel, inon, tin, or lead, comes in contact with copper in the A previous attempt to solder over these failed flat seam joints was not successful presence of water. Aluminum and zinc

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are the most susceptible to this type of corrosion, Proteclive measures in- clude painting the aluminum, steel, or The ManyVirtues of Copper iron with a bituminous or zinc chro- mate primer, S'n." antiquity, copper has been aprizedbuilding material used for roofìng, flashing, and intricate ornamentation. lt is a highly durable metal The roof should be detailed to prevent which can easily be shaped, stretched, or drawn for use in wiring, or runofffrom copper surfaces from rolled, hammered, or beaten into sheets without craclmarble, limestone, welded, or brazed, making it a very accommodating material for on-site granite, and bricl<. A properly detailed installation, lt is Íre-resistant, and has passed the Underwriters Labora- ddp edge between 314" and l-112" tory's most rigorous test for wind-resistance, making it an excellent wide can help prevent this, Gaslsulfate. The patina fìrsl appears as a dull brown and then feasible or reliable, Atlempting to re- gradually changes to blue-green, This weathering process takes only B to solder seams, for example, will serve l0 years to achieve in our highly acidic atmosphere. Lead-coated copper only to aggravate the problem failed of will develop an equally desirable soft gray color overtime, seams, Whether installing a new copper roof or replacing an old one, There are three types of copper: the following recommendations will Soft copper is highly malleable, mal

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accommodate thermal movement, the roof that may let water in, Hid- . Continuous locl< strips can secure den copper cleats should be used to copper edges while providing for attach the copper roofto the substrate, expansion. (Please see lllustration A allowing for unrestrained horizontal below.) system movement while providing . Carefully detail installation require- vertical resistance/restraint against ments: ln flashing situations, frequent wind uplift forces, restraint (nailing) of the copper will . Choose the correct joint or seam help avoid buclcling and provide designr Special joints and seams are control led expansion/contractìon, required in different sìtuations to aid Copper roofìng, however, needs to in copper's natural expansion and move freelyto help avoid metal contraction. For example, loose-lock fatigue, and the number of restraints seams allow copper panels to slide should be limited. Fewer restraints during expansion and contraction. Standard industry details must often be customized to specific field conditions. also mean fewer punctures through Batten seams also allow movement along the sheet length while enabling the copperto flex and expand be used. Lead-coated copper calls for between the base ofeach batten. 60%tin - 40% lead solder, ln many (Please see lllustration B on page 6.) cases, copper roof panels are "pre- Batlens of this type also serye as tinned" - cleaned, fluxed, and then expansion joints in a flat seam roof dipped into molten solden priorto where small copper sheets are installation. Pre-tinning creates a soldered togethe¡ forming large areas, stronger bond for the roof seams, which in turn require expansion relief adding increased protection against . Plan for insulation: ln existing water penetration. Rosin flux is usually structures, conditions may not allow for used to prepare the copper surlace Typical Fixed Cleat the necessary increase in height above priorto soldering, lf acid flux is the deckto accommodate code- chosen, however, the copper surface compliant insulation, While not always must be thoroughly ninsed afterwards feasible, an alternative may be to add to prevent pitting. insulation below the decl< Whatever . Select the right fafieners: All the solution, all insulation considerations fasteners should be of hard copper, must address condensation of interior vapo¡ taking into account the dew point location. . Properly prepare the substrate: Expansion Cleat Sheathìng for copper roofìng is typically plywood, topped with asphalt-saturated roof ng feltto create a cushion base for copper panels, EPDMs or self-adhering so lder lock strip modifìed bitumens are sometimes used continuous in place of felt Rosin paper slip sheets are installed over the felt to keep the copper sheet from adhering to it, which would compromise the coppers ability Lock Strip to expand and contract. . Choose the correct solder: Cold- copper requires a solder of 50% lllustration A: Cleat and lock strips rolled The substrate must be tested for pull-out provide securement to the deck while tin and 50% lead. For lead-free resistance to determine the most appropri- allowing for expansion and contraction. installation, 95%tin - 5% antimony can ate fasteners.

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copper alloy, or brass, except for washers and expansion shields, which can be made of lead, bronze, rubber, Fire Hazards in or plastic, Nails are best for flashings, R"placing at gravel stops, and on eave strips. Copper Roo g Screws are called fon when the copper fin must be held rigidly in place, such as at a ridge roll exposed to severe wind or if expansion shields have been required for a masonry substrate, Screws should have round heads and flat seats that won't puncture the copper roofsurface. Copper caps can be soldered over screw heads in gutters Below is a summary of relevant temperatures and other areas ofheavy water for the materials involved in copper roof installation; exposure to limit the potential for water intrusion. Copper button-head Rosin paper and plywood ignition temperature 492" - 496" F rivets are commonly join used to seams 50% Iinl50% lead solder solidus temperature 361'F which do not need to accommodate 50% Iinl50% lead solder liquidus temperature 471" F Average soldering temperature with hot irons 400" - 600. F Torch temperatures o^^o tr

The industry standard (and preferred method) for soldering calls forthe use of heated copper or brass bars, which are heated either through an attached or separate heat source, open flame torches are not recom- mended but are quite common on many job sites. While torches may offerthe easiest and fastest method of installation, they also create the greatest flre hazard, and require great skill and care by the installer. on the other hand, heated soldering irons, with tips of copper or brass bar, require constant attention to maintain the required level of heat, but do The finished batren seam roof provides not reach the temperature extremes that torches strong visual lines. will, and thus minimize the danger offìre.

Following expansion and contraction, with solder the guidelines below can provide the best protection against heat and fìre damage used to provide water-tightness. Be during soldering operations, These guidelinãs should be wary of pop rivets; if used, these should included in the specifcations, have brass mandrels, not steel, I Require all contractors and subcontractors working on the roof to provide a detailed fìre safety and lre avoidance plan. Hoffmann Roof types Architects recommends that this plan include a f re watch for up to There are three basic types ofcopper three hours after soldering activitres. roof designs, with each offering a 2. Use only heated irons for all rooftop soldering. specifìc benefìt to meet a given fìeld joints condition or design intent, lllustrations 3 Pre-tin all which will help reduce the time needed to sweat the joint ofthe seam types used in these roof and reduce the amount of heat required to properly solder the joint, designs are shown on page 6, 4 lf appropriate or practical, replace the rosin paper slip sheet with a non-combustible fìberglass product, Bctten seam roofs are often used on 5, Pre-fabricate all penetration curbs and sleeves away from the barrel vaults, domes, or cupolas, This substrate priorto installation. I seam type creates a deep, well-defined roof line or shadow, and allows for

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unique shapes. Batten creation of The Facility Manager's Boolcslaelf: Copper Roofing seams are created by usrng coPPer panels, set parallel to the roof slope, A. Basic References which are separated by a wood batten This batten provìdes the framework Copper in Architecture Hondbook. Copper Development Association, 260 forthe distinctive box shape of the lYadison Avenue, New York, NY 100 16. (800) 237-3282 or (212) 751- seam. The batlen cap provides water- 7 200, f ax (2 I 2) 757-7 234. tightness whtle accommodating Handbook, bound in 3-ring binderwith information, details, and guide exPansron. specifìcations on sheet coPPer applications in roofìng' gutters, flashing, expansion joints, etc,, $85,00 Flot seom rooþ are unique to coPPer CAD Diskettes: Four "AutoCad 12" diskettes of sheet copper details, and are usually found on a low-pitch g4O,OO Video: six-tape series, $40.00. Catalog also available roof (below I -in- 12") or on curved surfaces, such as domes and barrel 2 Copþer ond Common Sense. Revere Copper Products' Inc. P O Box 300, (3l5) 338-2022, fax (3 l5) 338-2224. From outside New vaults. Flat seams are either flctJocked Rome, NY 13442. (8OO) 448-1776. Other information on sheet copper is also available. or so/dered, depending on the roof Yorkr slope. Typically, the greater the slope, 3 Architecturolsheet Metol Monuol, Fífth Edition, | 993, $ | 4 I 00 CAD version, (continued on poge B) $425 OO. Stondord Proctice in Sheet Metol Work 1979 (reprinted by SMACNA as a reference for work on oìder buildings), $ l5 1.00. Sheet Metal and Air Conditioning Contractors' National Association' 420 1 Lafayette Center Drive, Chantilly, VA)2071 (703) 803-2989, fax (703) 803-3732

4 Soldering Monuol, $3200. American Welding Society, 550 N.W. LeJeune butyl tape or Road, lYiami, FL 33126 (800) 334-9353 fax (305) 443-7559 sealant at low Pans slope roofs 5 Metols in Americo's Historic Buildingsl Uses ond Preservotion Trectments Margot Gayle, David W, Look, AlA, and John G, Waite, AlA. National Park Service, Preservation Assistance Division, 1992 (update of l 9B0 edition) l 68 pages' 183 illustrations. GPO Stock Number 024-005-0 | l0B- I $ l0 Contact the

cl eat Superintendent of Documents at (202) 5 I2- I 800 for credit card orders

Standing Seam B. Technical Articles from Ihe Construct¡on Specifier

To order reÞnnts, contoctthe Construction Specifcctions /nstitute ot (800) ó89-2900 Repínts ore $4.00 eoch, $10 00 mintmum order. l. Cechvala, Steven, "Crafting the Custom Sheet Metal Roofl" Ihe Construct¡on cl eat Specifler, November 1989, Volume 42, Number I I p. I l6-120 Pan 2. Copper Development Associatlon. "Sheet Copper Fundamentals," The Construction Specifier, January 1995, Volume 48, Number | ' p. 48-63 3. Weaver, Martin E, "Copper Top," The Construction Specifier, November 199 l, Volume 44, Number I I, 40-46. Batten Seam P.

C. Other Technical Articles

soldered cì eat l. Copper Development Association, "UL's Highest Winds Can't Topple

ioint Copper Roof ng," CopperTopics, Winter 1996, p' I 7. "Copper Roofìng Design," Progressive Archttecture, August 1990, p. l5I 3, "Copper Roofìng From the Bottom Up' RiE/ lnformotion Letteri Spring 1992, p, 7, Roofng Industry Educational lnstitute, Englewood, CO (303) 790-7700 Flat Seam E-mail: REIROOF @ aol. com, 4. Thompson, Craig L. "What Are Some of the Fundamentals of the Copper Top?" Professionol Roofing, | 993, p' 40-43' lllustration B: Each of the three seams iune above is best suited to a specific roof condition or design. Compiled by Alan P Eddy, Technical lnformation Specialist I

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Volume l5 Number I

R E P R E S E NTAT tV E P R O I E CT S Copper Roof Rehabilitation

Hoffmann Architects provides investiga- Once the repair method has been Saint Theodosius Cathedral tion, design, and construction adminis- selected, the flrm prepares detailed Cleveland, Ohio tration services fon copper roofìng for a plans and specifìcations for competitive (Saint Theodosius Cathedral) number of clients, including worl< on bidding. On-site prolect staffand

private and public facilities The fìrm is contract ad m i n istrators tracl< the The Hartford Fire lnsurance Company often called in by major corporations, progress and quality of construclion Hartford, Connecticut private institutions, and real estate throughout the prolect. (lTT Hartford) owners to provide specialized consult- ing on the rehabilitation of deteriorated The following is a sampling of the fìrm's Congregation Rodeph Shalom copper roofìng. work in copper roof rehabilitation: Bridgeport, Connecticut (Congregation Rodeph Shalom) Hoffmann Architects' worl< begins with Smithsonian lnstitution an in-depth analysis of the existing roof Patent Office Building New York Stock Exchange and struclure to determine the scope Washington, District of Columbia New York, New Yorl< and causes of damage and deterioration (Harlman-Cox Arch itects) (New York Stocl< Exchange) problems. The fìrm's architects and engineers research and evaluate repair Bronx Community College 3 l0 Orange Street options based on technical merit and Gould Memorial Library New Haven, Connecticut ability to meet budget and life cycle Bronx, New Yorl< (Southern New England Telephone) goals, occupancy needs during con- (Dormitory Authority of the State of fruction, and aelhetic consider¿tions. New York) Rockefeller Center Complex The prolect team's efforts include New York, New York careful research into the building's United States Courthouse (Rockefel ler Center lYanagement architectural history to ensure that 40 Foley Square Corporation) I detailing and restoration wort is New Yorl<, New York consislent with the style of its time, a key (Brennan Beer Gorman Architects/ consider¿tion when restoring historic GSA) structures,

The Performing Arts Center at Kingsborough Community NYNEX, 104 Broad Street, New York, New York. College in Brooklyn, New York.

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the less need for solderto create a T o CZÈõo ¡i Þã watertight bond. 7 u.,l f, ã - ci+ -r-t(rMtJ :> JJ l¿ - U The stcnding seom roof is either field- O\OPP lr Z ôlûq dP formed or constructed of pre-formed C) öo9 o= o panels of I B" to 24" widths which are Z o-- (J =Þl< placed parallel to the roof slope and Õloo joìned U C.c to other panels using a double- U no F C locl:t With proper detailing and carefully m o supervised ìnstallation, new and 'l o replacement copper roofs can provide Z v a handsome return to building owners om An c in both endurance and beauty. m Ø arch itect well-versed in traditional --1 m steep roofìng techniques and who has U wide experience in roofìng, water- proofìng, and sheet metal worl< is the best candidate for this prolect type Worl

Please send news, technical informa- tion, address changes, or requests for free subscriptions to Emily D, Dowden, Ed itor, H offmann Arch itects{OURNAL at 432 Washington Avenue, North Haven, Connecricut06473 or l2f0 Avenue of the Americas, New York, New York 10020.

For answers to specifìc questions or for information on the services we offe¡ please call Brian W, Schafer at (203) 239-6660 or (2 I 2) 9s7-8940. This copper roof failed after 70 years of service and acid rain.-

Editor: Emily D, Dowden Grophic Servlces; Bligh Graphics Editonol Servrces; Jonelle Lawhorn Hobbs Communications I