Hoffmann Architects
Second Issue 1992 Volume l0 Number2
Avoiding Added Wear and Têar to Roofing
ln these situations, roof damage occurs Richard P. Kadlubowski when:
A hnorgh,today's roofing systems r Roofìng equipment is improperly are highly durable and well-designed installed directly on the roofìng for their pri mary weatherproofìng membrane, without adequate function, they are not usually ìntended securement to the supportive or manufactured to support weìght- su bstructure. bearing loads of either equìpment or foot trafiìc, r Routine maintenance and emer- gency repairs require foot tr affìc All too often, however, the roofìng across inadequately protected system is asked to do justthat, These roof surlaces. secondary uses can play a leading role in shortening a roof 's lifespan and I Accessed and terraced roofs have creating unnecessary maintenance and insuffrcient drainage systems and repair problems, But there are ways to wall
f t r m's d rofti n g d ep o rtm e nt. dishes and other communication
Copyright Hoflmann Architects | 992 Hoffmann Architects / Journal
ln Pursuit of Positive Drainage
A moilure that is allowed to collect on ", top of the roofìng membrane is a leak waiting ment? Will equipment needs to happen Even the smallest opening in the '*,r*lç change as tenancy changes? How roofìng system can lead majol water to will replacement af[ecl the erisLing damage if a source of moistur e is readily at ' a-lt-" roofing system? When ìt's time to hand. replace the equipment will the The solution: Remove the water. existing suppoft be suffìcient? The strategy: Ensure positive slope to the roof drainage system 3. ls the roof adequately protected The variety of roofìng systems available today with wall In lieu of drainage channels for masonry ballast systems, a pedestal sylem can be used. The pedestals elevate the masonry units and allow water to flow beneath the ballast. Drains then remove the water at the membr¿ne level. Various promenade or bilevel drzins can be used in this type of roof installation. (continued) I 2 3 2 Standing water - a sure sign of insuffìcient A basic, step-by-step guide to proper flashing techniques. Vulnerable corners must be slope for proper drainage. wrapped to ensure water-tight barriers. 2 Volume l0 Number 2 d ln Pursuit of Positive Drainage (cont¡ These collect the bulk of the water at the membrane level and surface runoff at the ballast level, while providing a clean profìle at the same height of the masonry ballast. Terroced Roofs :-.- r'€. Terr¿ced roofs present the greatest challenges to water drainage. Here, many of the walking surfaces are mortar-setting beds fìnished with quarry tile, with the bed typically laid directly over the membrane When probed, these setting beds have often been found to be saturated. Neitherthe tile nor the mortar are waterproof thus allowing water to collect within the matnx of the bed, ln order for the sylem to drain and dry out, the moilure must leach through the depth ofthe settrng bed to reach the roof-level drains a long, slow process. One way to speed -up the process and minimize water satur¿tion problems is the installation of specially designed drainage materials between the roof membmne and the beds. These drainage matenals combine a fìttering fabric Poured concrete support pads are improperly placed directly on stone ballast. adhered to a porous fìller. The fabric allows water to drain fom the setting bed to the rooftop, while the fìller maintains adequate of the lnsulation will also lessen its Wìndow washing rigs olfer their own space for water to flow through to the insulating value, leading to increased set of problems, These include drainage system. heating and cooling costs, excess¡ve loading, added maintenance Bilevel drains handle water flow fìom both traffìc, and the potential for hydraulic the tile level and membrane level, reducing lYechanical vibrations caused by fluid leal 3 Hoffmann Architects / Journal Flashing and terminations are the next Accessed and Terraced Roofs line of defense in creating watertight lf the roof is usable space, it can transitions between the roof and technically be considered part of a equipment and other accessories. waterproofìng system, rather than While proper fìashing techniques are simply a component of the building worthy of a separate article, two basic envelope, as a non-accessed roof principles are worth noting here: would be. This is a key consideration when it comes to manufacturers' Layering uses various flashing materials warranties, lYost manufacturers will that are bonded together to prevent not warranty their roofìng product if water entry, This technique creates it is used as a waterproofìng system. Large support bases for satellite dishes multiple barriers that blocl< potential This situation occurs most often when evenly distribute imposed loads. water entry, the roof is used as a terrace or when window washing runways are ìnstalled, brane, In this way, equipment is sup Placement of terminotions should be The facility manager should be aware ported by a stable substrate and any above the level of possible standing of warranty restrictions when determin- negative impact on the roofìng water and secured to a sound sub- ing rooftop uses, membrane and system is reduced or strate. Termination bars and cap eliminated, flashings use compression and coverìng Roof terraces typically call forthe to prevent water entry, placement of wall Proper drainage for the jogging tracl< is achieved by protection mats installed under the tracl< and surrounding stone ballast, along with a correctly pitched slope on the concrete decl< below. 4 Volume l0 Number 2 Window Washing Rigs: Selection and Installation Wroo* washing rigs can herp ease one of a facility manager's most tedious maintenance chores. But they can also open up a whole new world of maintenance and roof preservation problems. The most signifìcant impact of this equipment is its weight. Self,propelled rigs weigh approximately 15,000 pounds, fai in excess of typical roof loading calculations. New construction must take this additional weight into considerztion when designing the structuml system In existing buildings, however, rig installation may not alr,vays be feasible. The cost of beefing up the building's load-bearing capac¡ty to accommodate the added weight could be prohibitive Therefore, all r-elevant design and structural issues must be investigated before installing this equipment. Window washing rigs also produce signifìcant vibration during operation, causing added stress to the building and roofing system. That vibration, in turn, can damage both the roof and the building's strrctural integrity. As well, having a window washing rig usually means a lot more people up on the rool w¡th both maintenance and (continued) For proper water protection, flashing terminations occur well above the finished roof level, with integral cap flashing to cover the assembly. of pr^otection boards, These liB' thicl< Conclusion sheets are usually a bonded composite The rooftop can be an ideal site for such of f rbrous material and asphalt, During secondary uses as equipment location construction, the boards are installed and tenant access, and these uses should overthe fìnished membrane and the not be avoided out offear of roof remainder of the roofìng system damage, The l 5 Hoffmann Architects / Journal Window Washing Rigs: Selection and Installation ¡cont,¡ operating stafftraipsing back and forth. The rigs should be installed for easy The Facility Manager's Bookshelf Roof Accessories maintenance access via a well-protected roof membrane. There are seveml basic types of mobile A. Basic References washing rigs and installation methods. L Ballast: One type uses a roof carriage that trzvels ANSI/R|4A/SPRI RP 4 l9B8 Wind Design Guide for Bollasted on a runway, usually poured concrete, Single-Ply Roofing I 5.00 resting on top of the roof membrane. Systems, $ Another is the rail-mounted rig, which To order: American National Standards lnstitute, Sales Dept., offers three infallation choices: ll West42nd Street, NewYorl<, NY 10036 (71))302-l)86 L The rail system is mounted above the 2, Roof Loads: roofìng membrane on suppoft stanchions ASCE 7-BB (formerly ANSI 458. l- l9B2) Minimum Desþn Loods which are tied ìnto the supportive structurc. for Buildings ond Other Structures, l0B pp, 1990,742-X $24.00 2. The system is mounted to the parapet To order: American Society of Civil Engineers, lYarketing Services, walls and securcd to the structure, 345 East 47th Street, New Yod<, NY 10017-7398, ()17) 705-7538. keepìng it independent of the roofìng system. 3 Drains: Cast lron Soi/ Pipe and Fittings Hondbook,7th 10.50 3. A fì.eely laid system, where the rails ar e edition 1990 $ supported on top ofthe roofìng To order: Cast lron Soil Pipe lnstitute, 5959 Shallowford Road, membmne. Suite 419, Chattanooga TN 37Ðl (615) 892-01 37. Each ng type and installation method has its drawbacks and advantages. The freely 4. Sheet lYetal: laid rail systems transmit unnecessary Architecturol Sheet Metol Monuol,4th edìtìon, 1987. $ I 13.00 loads and vibrations to the roofìng membmne, leading to undue stress on the To order: Sheet lYetal and Air Conditioning Contractors' National roofìng system. Repairs can be more Association (SMACNA), 4701 Lafayelle Center Drive, Chantilly, difiìcult and costly, as they usually require vA220t-t709 (703) 803 2980 disassembly of the rail system. B. General Reading On the other hand, the mass and size of looftop runways for carriage rigs are l, Roof rng Details: benefìcial in evenly distributing the weight lYcCampbell, B, Harrison, Problems in Roofing Design. 1992. across a broader expanse ofthe roof 224 pp,, IBSN Vibrztion pr.oblems are similady reduced. 0-7s06-9162x., $39 9s But runways tend to encourage moisture To order: Butterworth Arch itecture, | -800-3 66-2665. retention, as water is trapped beneath the concrete and kept in direct contact with C. Construction Specifìcations lnstitute the membrane. lf leaks occur, repairs Specifìer Reprìnts could require the removal of the rr.rnway 60 I lYadison Street an intensive and costly proposition. - Alexandda V A 773 I 4- 179 I The most widely recommended solution (703) 684-0300 is a rail-mounted system that is attached to the roof deck or to the parapet, These Cost: $4,00 each, $ 10,00 minimum order. VA residents add 45%Iax, systems typically present fewer main- tenance problems and leduce the risk l. Heineman, Paul. "Coping with Membrane Roof Penetrations." of damage to the roof Both installation The Construction Specifier, November l9B7, p,36, methods usually conform to manu- facturerc' wan-anty limitations for roofìng 2. Reidel, George C, "Ghost Leal Compìled by Alan P. Eddy, Records and lnformation lYanager I 6 Volume l0 Number 2 R E P R E S E NTAT tV E P R O I E CT S Roof Rehabilitation Hoffmann Architects specializes in the Time-Warner Building Yale Press Building rehabilitation of the exledors of existing New York, New Yorl< New Haven, Connecticut facilities. A major porlion of the fìrm's (Rocl Tower at Yale Kline Biology University, New Haven, The Hartford lnsurance Company Headquarters complex in Connecticut. downtown Hamford, Connecticut. 7 ì Hoffmann Architects / Journal T o ruaü )) eV Ni Þ* ã J=< ct+ Staff News ÚIP J¡ v Yi- U \o P z ô-rcO\O l dP Professional Accompl ishments: C) oo: o= Z U' l<:Þ FAIA was elected U John J. Hoffmann, to ôloo the Board of Directors of The Avenue U ôrDEf. c U L Ð of the Americas Association, a non- m O c¡. profìt civic association based in New ô -È! o W Yorl<, F P ôm --l Jane B. Beaudry has been elected a o vice president of the Housatonic Z v of the Constructìon Specifìca m Chapter O C tions lnstitute, m --l m U Roy C. Olsen, AIA has been desig- nated a Certifìed Construction Specifìer by the Construction Specifìca- tions lnstitute, Alan P. Eddy has been elected presi- dent of the New Haven/Bridgeport /OURNAL is a publication of Hoffmann Architects, specialists in investigative Chapter of the Association of Records and rehabilitative arch itecture/engi- Managers and Administrators, His neering, including the analysis and "Reducing arlicle, Energy Costs by solution of problems within roofs, Controlling Air lnfìltration", appeared in exterior walls, glazing, and struclural the lYay/june 1992 issue of AIPE systems of existing buildings, plazas, Facilities, a publication of the American and parking garages. lnstitute of Plant Engineers, Please send news, technical informa- tion, address changes, or requests for Harwood W. Loomis, AIA has free subscriptions to Brian Schafer, rejoined the fìrm as Senior Architect Ed itor, Hoffmann Architectsf OURNAL and Project lYanager. He is currently at 432 Washington Avenue, North Haven, Conneclicut 06473 or 1270 serving a one-year term as vice Avenue of the Americas, New York, president of the Connecticut chapter New Yorl< 10020, of BOCA (Building Offlcials and Code Administrators lnternational) and is a For answers to specifìc questions or lor informatìon on the services we member of the AIA ad hoc tasl< force offer, please call Brian Schafer at reviewing HUD procurement policies (703) 739-6660 or (2 I 7) 332 1320. and Standard Owner-Architect documents. r Editor : Brian Schafer Grophic Servlces: MossWarner Communications, Inc, H u Editoriol Services ; .J onelle Lawhorn obbs Comm nications I