THE HISTORY OF FLASHING AND ITS IMPORTANCE IN
BOTH MODERN AND HISTORIC MASONRY CONSTRUCTION
JEFFREY L. ERDLY AND GREGG M. BEKELJA MASONRY PRESERVATION SERVICES, INC. • BERWICK, PA
S YMPOSIUM ON B UILDING E NVELOPE T ECHNOLOGY • O CTOBER 2 0 0 8 E RDLY & B EKELJA • 9 7
ABSTRACT Through our firm’s 23year history as a specialty masonry restoration contractor, it is our observation that no single building component impacts the performance and/or the longevity of a building envelope more than the proper detailing and installation of workable flashing systems within a wall. Since the introduction of carbon steel into mass masonry structures during the late 1800s, the importance of proper flashing installation and its abil ity to reduce leakage, corrosion, and their consequences cannot be over emphasized. This paper will discuss the impact of flashing design and installation in buildings that include mass masonry, cavity walls, and terra cotta.
SPEAKER
JEFFREY L. ERDLY — MASONRY PRESERVATION SERVICES, INC. • BERWICK, PA
JEFFREY L. ERDLY is the CEO of Masonry Preservation Services, Inc. (MPS). A member of ASTM International, his activities include cochairman of task group E 06.55.05, and co editing of both STP (Special Technical Publication) 1314, “Water Leakage through Building Facades,” and STP 1444, “Building Façade Maintenance, Repair, and Inspection.” Erdly is also a past president of the SWR Institute and recently received an award of special recog nition from ASTM Committee E06 regarding his contributions to the society. Jeff has pre sented in excess of 100 technical seminars and original technical papers throughout the United States for other organizations, including RCI, APT, ICRI, the University of Wisconsin, and MIT.
COAUTHOR
GREGG M. BEKELJA — MASONRY PRESERVATION SERVICES, INC. • BERWICK, PA
GREGG M. BEKELJA is the president of MPS, a specialty building façade repair con tractor located in Berwick, Pennsylvania. Gregg is responsible for project estimating, pro curement, project management, and implementation of corporate safety guidelines. He has been a member is the SWR Institute since 1994. He is also a member of the American Institute of Architects (AIA) and ASTM International.
9 8 • E RDLY & B EKELJA S YMPOSIUM ON B UILDING E NVELOPE T ECHNOLOGY • O CTOBER 2 0 0 8
THE HISTORY OF FLASHING AND ITS IMPORTANCE IN
BOTH MODERN AND HISTORIC MASONRY CONSTRUCTION
THE HISTORY OF Figure 1 – Recommended flashing detail from architectural
FLASHING graphic standards. Facsimile of original edition. Numerous technical manuals published dur ing the early 20th century Figure 2 – Copper cup (thimble) included detailing at ma from a circa1930s project. sonry parapets requiring throughwall flashing at two levels. This detailing, contained in both of the most widely respected standards of the day, Architectural Graphic Stan dards1 and Brick Engi neering Handbook of De sign,2 required throughwall flashing at both the roof base flashing level and beneath copings (Figure 1). Further exten STANDARD sive detailing was also included in these DETAILING manuals regarding the use of copper cups Working in (thimbles) to be used when flashing or roof concert with ing was pierced by pinning that was re many leading quired to secure copings or reinforce para forensic engi pets (Figure 2). Additional flashing details neers and arch for terra cotta assemblies were also rec itects, we have helped develop details that showing these concepts. The authors of this ommended as best practice. The terra cotta follow the original principles and provide for paper have participated in the evaluation industry as a whole ignored these recom longterm preservation of masonry struc and repair of numerous masonry struc mendations, which eventually became a tures. Central to these goals is the concept tures. Following the concepts outlined contributing factor to its near demise. that masonry repairs should be detailed above, some of these structures were also Many modern roof termination stan using materials and strategies that dards in use today violate these original acknowledge that masonry and flash principles by allowing the use of a termina ing materials should be expected to tion bar surfacemounted onto masonry or perform for 50 to 75 years, while roof other materials. These widely used flashing ing membranes may require replace terminations fail to preclude moisture from ment every 20 to 30 years. Further circumventing the surfacemounted roofing more, it is often not possible or advis termination and lead to leakage and accel able to demolish and rebuild parapets erated roof and masonry failures (Figure 3). to a level where rooflevel throughwall Other detailing errors commonly observed flashing can be installed. include: 1) improper use of EPDM mem To protect parapets, throughwall branes as parapet covering; and 2) the flashing beneath copings is critical. extension of base flashing above existing Proper flashing should: 1) protect pin flashing necessitated by the addition of roof ning with a thimble assembly; 2) inte insulation. grate a flashing extension outboard An additional improvement to the origi that both daylights and includes a nal flashing details noted previously would drip; 3) integrate a flashing extension be to extend all throughwall flashings inboard, including a receptor to beyond the face of the wall (daylight) to form accommodate roof counter flashing or a drip intended to divert water traveling rain screen; and 4) be permanently down the wall out away from the wall below. sealed with rubberized asphaltic Figure 3 – Water penetration circumventing flashing. See Figure 4 for a detail surfacemounted roofing termination. S YMPOSIUM ON B UILDING E NVELOPE T ECHNOLOGY • O CTOBER 2 0 0 8 E RDLY & B EKELJA • 9 9 Figure 4 – Proper flashing beneath copings.
Figure 5 – EPDM roof membrane terminated at cast stone parapet.
repaired incorporating provisions to accom modate future roofing installations.
CASE STUDY 1 This academic building was constructed in the early 1920s and included multi wythe mass masonry walls with cast stone copings and trim, and a center tower com posed of solid cast stone components. The masonry was constructed without through wall flashing. The center tower, composed of solid cast stone, was reroofed using EPDM as a replacement roof, installed with a sur facemounted termination bar (Figure 5). The new roof termination leaked, and to repair this assembly, the copings were removed and pinned, and throughwall EPDM roof termination below (Figure 6). detailed or constructed. The most labor flashing was installed and the copings intensive and difficult masonry flashing reset. On the inboard face, a receptor was CASE STUDY 2 interface detailing occurs when a raked roof installed to accommodate a rain screen The two examples cited include a new adjoins a vertical masonry rising wall panel, which also oversails the counter brick/limestonetrimmed highrise that (Figure 7). Proper detailing at these inter flashing, thereby protecting the deficient experienced cyclical and widespread leak faces requires 1) a throughwall stepped age since its com panabovepan installation (Figure 8); 2) pletion, and a provisions to accommodate stepped surface 1960s church counterflashing down the rake; and 3) clad with orchard detailing to accommodate sufficient wind stone. Both pro clips and weeps. The proper installation of jects included this detail requires a combination of mason flashing that was ry, sheetmetal, and roofing skills. This type not improperly of repair can become even more complicat
Figure 6 – Rain screen panel system interfaced with coping flashing and extending down over EPDM roofing termination.
Figure 7 – Copper roofing improperly terminated at raked masonry rising wall.
1 0 0 • E RDLY & B EKELJA S YMPOSIUM ON B UILDING E NVELOPE T ECHNOLOGY • O CTOBER 2 0 0 8 Figure 9 – Stepped pan flashing at raked stone rising wall.
Figure 8 – Installation of copper steppedpan flashing at raked rising wall. ed when natural stone masonry varying in direct contact with brick and mortar, cor assembly (Figure 12). coursing height and length requires a roded in the presence of moisture over time, steppedpan flashing installation (Figure 9). and the volume change created by the exfo Flashing and Terra Cotta liating rust (oxide jacking) caused the Glazed architectural terra cotta’s use
CASE STUDY 3 masonry to split and become unstable and the subsequent demise of this industry When restoring any masonry structure, (Figures 10a and 10b). Rebuilding these were partially caused by the failure of it makes sense to first understand all of the details without provisions to protect new designers and manufacturers to under causes of the deteriorative force prior to steel (including the introduction of through stand the need for flashing. Because of terra designing a repair. In the case of landmark wall flashing) fails to address the original cotta’s use as a decorative material and structures, it is important to assess the cause of the deterioration. For this project, alternative for cut stone, many decorative value of introducing flashings into the the parapet was recon remedial design, even if the end result is a structed to include new slight change or the addition of a flashing throughwall, leadcoat line that will afford protection to the assem ed copper flashing bly and extend its service life. The exact above new steel hangers reproduction of a detail prone to accelerat (Figure 11) and extend ed failure in the name of preservation seems ed inboard to interface wasteful and not congruent with the true with new roofing, there intent of preserving significant architecture by providing a unified for future generations. roof/flashing interface This landmark structure was modeled that extends through after the Italian Renaissance style and is the historic masonry rich in corbels, Gothic arches, and ornate brick and terra cotta. The 200fttall smokestack tow Figures 10a (left) and 10b (above) – er, located within Displaced brick masonry caused by oxide a federal peniten jacking of embedded steel hangers. tiary, was con structed as a mass masonry wall with embed ded carbonsteel hanger assem blies. The steel hangers, in S YMPOSIUM ON B UILDING E NVELOPE T ECHNOLOGY • O CTOBER 2 0 0 8 E RDLY & B EKELJA • 1 0 1 Figure 12 – Leadcoated copper flashing added to protect embedded steel.
Figure 11 – Detailing of tower parapet with throughwall flashing added. terra cotta assemblies were hung or sus have been confined to short periods struction” recommends that the manufac pended from mild steel anchors and hanger and to a few localities. In modern turer who knows terra cotta is best assemblies. Failure to protect these steel times the creator of the skyscraper – equipped to also install it. In this article, the components (iron anchors) from moisture the progressive American Architect – following statements are made with regard created a domino effect failure of entire working with the responsive and to extreme exposure without deterioration. assemblies as unprotected anchors expand enterprising Manufacturer, rediscov ed due to corrosion. ered, improved and gave to an appre The greatest agent of deterioration is A consortium of terra cotta manufactur ciative Public this most durable and water, and water works in three ers (The National Terra Cotta Society) pub versatile of all building materials. ways: (1) in a smoky atmosphere it lished Architectural Terra Cotta Standard reacts with accumulated soot to form Construction in 1914.3 At that time, no rec Today it is a matter of common sulphurous and sulphuric acid; ommendations for the use of flashings or knowledge among Architects that (2) inferior mortar is absorbent and the coating of iron anchors were made with modern Terra Cotta possesses many swells under the action of water; in this standard. Following is a portion of superior qualities; that it may be eco (3) accumulated moisture in a freez the foreword contained in the 1914 stan nomically made in an endless variety ing temperature will expand with suf dard. of forms and colors; that, if well ficient force to shatter Terra Cotta or made, properly set and carefully any other structural material. The use of burned clay were [sic] in pointed it is permanently enduring the form of brick, tile or pottery has and resists successfully the ravages Generally it is advisable to flash been uninterrupted and universal of water and fire; that it combines wash courses with copper, particu from the dawn of civilization to the lightness with strength and beauty larly in a cold climate. The flashing present day. The use of burned clay with usefulness. should be secured by lead plugs on in the form of Architectural Terra the nib of the wash member, placed Cotta has been more sporadic and This foreword clearly represents most in the joints between the pieces of local. Its unequalled merits as a manufacturers’ thinking of the time, with Terra Cotta or in plug holes provided building material were fully appreci bold statements regarding terra cotta’s for the purpose. Securing flashing by ated by the Greeks and Tuscans superior qualities, including its touted per plugs is better than fastening in a who, two thousand years ago, used manent endurance and resistance to the raglet, because the raglet will have to it to face the perishable stone in some ravages of water. However, in a monthly be filled with some composition. If it of their Temples. Centuries passed, newsletter published by Atlantic Terra is not completely filled, water will col during which the art of making Cotta, Volume I, Number 9, July, 1914,4 an lect and oxidation of the metal result, Architectural Terra Cotta seems to article entitled “Correct Terra Cotta Con and sometimes the very compositions 1 0 2 • E RDLY & B EKELJA S YMPOSIUM ON B UILDING E NVELOPE T ECHNOLOGY • O CTOBER 2 0 0 8 used for filling raglets corrode and Expansion Joints ports, ties, etc. Where such protection destroy the flashing instead of pro Proper provision should be made for cannot be permanently secured tecting it! expansion joints at shelf supports, through encasement with mortar or over column caps, etc., to prevent the concrete or through the use of corro Iron anchors also require some atten development of disruptive stresses sion resistant metallic coatings, non tion. Ordinarily, they are fully pro caused by deflection, wind pressure, corrosive metals should be employed. tected by being imbedded in the temperature changes, settlement and masonry or concrete backing, but to like forces. Freestanding Construction insure [sic] complete protection from Exposed freestanding construction, rust, they should be coated with Terra Cotta on Concrete Frames subject to the absorption of water some noncorrosive paint. The volume changes incident to the through mortar joints and liable to setting and hardening of concrete injury from subsequent freezing, or After reading the Atlantic Terra Cotta and the variations in volume of con the expansion of improper filling newsletter, also published in 1914, it is crete due to humidity and tempera material, should generally be left clear that problems within the terra cotta ture conditions, require provisions to unfilled and should be ventilated by industry had already surfaced by that time. allow free movement of the support means of small, inconspicuously The National Terra Cotta Society pub ing frame and make it undesirable to placed weepholes (indicated by W. lished a revised edition, entitled Terra Cotta completely fill a facing applied to a 11. on the plates). Standard Construction, in 1927.5 The follow concrete structure. ing statements contained within the revised Flashing and Drips standard’s introduction give a sense of Protection against Corrosion Properly constructed flashing should problems identified within the industry. Proper care should be exercised to be provided to cover the top of large prevent the corrosion of all steel sup projecting horizontal courses, the The changes made in backs and tops of parapet this revision are the re walls, wideexposed sill cours sult of a more extended es, etc., and all projecting fea experience in manufac tures should have drips. turing and in modern building methods, and Most failures of glazed are based on a careful architectural terra cotta can be study of the behavior attributed to a misunderstand and weathering proper ing of the vulnerability of car ties of exterior building bonsteel anchors contained materials. The following within terra cotta assemblies. are the most important of Given modern materials (stain the structural principles less steel hangers) with good upon which this revision flashing installation and has been developed: detailing, glazed architectural terra cotta can provide long Shelf Supports term performance. In concrete or steel frame
buildings, the veneer or CASE STUDY 4 facing material should This historic structure, be fully and continuous located in the Piedmont region ly supported at each of North Carolina, was con floor level on shelf sup structed in 1921. The building ports of adequate used architectural terra cotta strength and stiffness, to form projecting balconies at rigidly connected to the two intermediate floors (Figure structural frame. Steel 13). The original construction shelf angles or supports, did not incorporate any flash in all cases, should be ing and/or noncorrosive located in mortar joints. anchors consistent with the The strength of the Terra 1914 standard. After approxi Cotta should not be mately 80 years of service, unnecessarily reduced expansion (oxide jacking) of by cutting the webs to steel components has compro receive the steel. mised the stability of the entire assembly (Figure 14). The Figure 13 – Terra cotta balcony assembly. authors of this paper partici S YMPOSIUM ON B UILDING E NVELOPE T ECHNOLOGY • O CTOBER 2 0 0 8 E RDLY & B EKELJA • 1 0 3 Figure 14 – Terra cotta components damaged by oxide jacking. pated in only the review of the structure recommended are still viable. 2. H.C. Plummer and L.J. Reardon, and did not participate in the repair or However, before jumping onto the flash Principles of Brick Engineering, repair design. ing bandwagon, designers should also heed Handbook of Design, Structural Clay Plummer’s quote contained in the Principles Products Institute, Washington, DC,
CONCLUSION of Brick Engineering Handbook of Design, 1939. Buildings require proper flashing at sited previously, as follows: “[A]t the outset, 3. Architectural Terra Cotta Standard many locations to withstand exposure to it might be stated that no flashing at all is Construction, National Terra Cotta moisture and liquid water. Roofs, masonry better than poor flashing.” Society, New York, NY, 1914. parapets, and building envelopes are easily 4. Atlantic Terra Cotta, Volume I, compromised by detailing that fails to pro FOOTNOTES Number 9, July 1914. tect components with workable flashings. 1. C.G. Ramsey and H.R. Sleeper, 5. Terra Cotta Standard Construction, Both building and design professionals Architectural Graphic Standards, rev. ed., National Terra Cotta within the repair, roofing, and preservation facsimile of original edition, John Society, New York, NY, 1927. industries would be wellserved to review Wiley & Sons, Inc., London, Chap standards published over 75 years ago, in man & Hall, Limited, New York, NY, which basic detailing and design concepts March 1932, 1990.
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