Fundamentals of Roof Lnspections by William M

first tects issue 88

Fundamentals of Roof lnspections by William M. Easterly

When the condition of a plant roof ates areas of special vulnerability on condition and have a clear water- is ignored, it can be expected to fail the roof. Shoddy details are the weak flow path. The flashing of drains, before it reaches half its designed life. link in roof system performance and downspouts, Butters/ and scuppers Deficiencies in the roofing system should not be tolerated. Typical should be in good condition. can result in wet insulation, which examples of poor design details in- Vents and projections should have causes loss of insulating quality, clude lack of adequate expansion flashings and counterflashings se- damage to decking, and leakage. The joints; inferior light gauge structural cured in place and intact. Counter- economic burden of such neglect is steel decks; penetrations through roof flashings should slope to prevent generally many times the cost of an ponded water. Projections such as ongoing roof maintenance program, stacks, vents, hoods, domes, and especially if the program includes umbrellas may be conductors of wa- regular inspections. ter because of design or deterioration; The roof should be inspected in the they should be in good condition and spring and in the fall after the leaves properly anchored. have fallen, when it is dry and surface Areas near mechanical equipment temperatures are less than B0 F. lt should be checked for leakage, vapor also should be checked after any condensation, i nadequate wal kways, severe wind, rain, hail, or snow and deteriorated or improper curb- storm. ing. Pitch pockets should be exam- Loose Flashing ined for filling. INSPECTION PROGRAM for equipment (vents, fans, etc.) with- Flashings and counterflashings at The intent of roof inspection is to out proper flashing; change in direc- parapet walls and around roof edges find irregularities that make the roof tion of structural decking without ad- and projections should not sag/ sepa- susceptible to damage. The investi- justment in flashing; and inadequate rate from the wall, buckle, crack, or gation should cover roof history, slope designed into a flat roof. show signs of weathering. design, current problems, testing, Drains and scuppers should be Cant strips also should be checked and evaluations. placed at the proper location and for any signs of deterioration. height and should not be clogged. Parapet walls should be checked DESIGN DETAITS The drain assembly, including the for cracks, open coping joints, or lmproper or careless design cre- clamping rings, should be in good deteriorated or porous mortar joints.

volume 6 number'l copyright Hoffmann Architects 1988 Built-up roofing systems should Debris on the roof may include Ponding and drainage problems, be checked for these additional sawdust, grain dust, sand, oil, grease, typically evidenced by standing wa- items: chemicals, solvents, vegetation, tree ter, result in softness or sponginess of Surface gravels should be firmly limbs, branches and leaves, or other the roof materials. ln addition, adhered to the roofing membrane. materials that can contribute to the ponding encourages growth of fun-

Al I igatoring or cracki ng of the smooth degradation of the system. gus or discoloration of the stone and roof surfaces, or exposed felts should degradation of the surface. be noted. The roof membrane should Taking a Roof History Leakage problems should be also be examined for curling, buck- - tracked with a log that outlines the ling, fishmouthing, and blistering. location, intensity, and weather con- Blistering and ridging indicate seri- ditions during the leakage. ln evalu- ous problems. ating and correcting current prob- Cracks and splits allow moisture lems, the following questions can into the roofing system. Evidence of help pinpoint the source of the prob- previous repair in a problem area lem: should be noted, as well as the near- Has the roof leaked in the past? est expansion joint and its direction Where does it leak now? relative to the troubled area. What preventive maintenance or , Expansion and control joints repairs have been done on the roof should be in good condition, as well recently? asseam laps, flashing, cantstrips, and Does the leak occur as soon as the membrane. ln addition, it is good rain starts, despite wind intensity or practice to check for any dryness, direction? brittleness, or splitting of bellows Does it occur after the rain starts material. but while it is still raining? Lap seams should be inspected for Does the leak stop immediately dried and brittle edges and felt ends. after it rains, or does the roof contin ue Loss of aggregate coverage and loss of to leak for extended periods of time? mineral surfaces on organic felts The interior of the building should occur with dryness. be checked for the following: Bare felts and wrinkles indicate a Leaks on the underside of roof generally poor surface condition. decking, along vertical walls, Spots where the membrane shows around columns, and around through the gravel and the edges of equipment attached to or roofing felts are no longer bonded extending through the roof together or are raised should be care- Discolored ceiling tile, rust spots, fully checked. peeling paint, warped or spalling deck material CURRENT PROBTEMS Straightness of walls, columns, and

The condition of the roof system is cei I i ngs also indicated by more obvious signs Erosion occurs where water falls Sagging roof structure. of deterioration: continuously on the roof, such as The building's exterior perimeter Falling objects such as tree limbs, around any open downspouts and should be checked for the following: debris blown from high to low roofs, open-ended condensate drains from Cracks, openings, deterioration, and copings and capstones falling from the cooling equipment. The condi- loose mortar in coping and joints parapets, and materials or tools tion includes the displacement of Separation of termination points dropped by workers can perforate the aggregate and the wearing of cap Splits or tears in flexible expansion roof's surface. sheet and felts. or control joints

2 Cracks in mortar, brick, or masonry service. As long as the insulation is not be corrected through repairs. lf Plumbness of walls dry and the substrate sound, only blistering of the membrane is severe, U nnatural configuration and minor repairs and maintenance are again the only solution may be total looseness of overhangs, fascias, required. replacement. Other conditions that cornices, Sutters, and down- lf the surface condition of the roof require immediate attention include spouts. looks bad, but there is no evidence of loss of the roof systems insulating leaks, the roof may be nearing the value and dead load design viola- TESTING end of its effective life. Expert advice tions. Under these conditions, the lf the roof is leaking internally, it is should be sought as soon as possible roof membrane must be replaced advisable to test for moisture content for analysis. even if the insulation retains its ther- of roof insulation. Nondestructive A roof that shows evidence of ridg- mal integrity. testing equipment scans the roof sur- ing, butdoes not leak, willsoon leak. And if the roofing system is ap- face to monitor the condition of the lf the flashings are in questionable proximately 20 years old, itshould be i nsulation. lnfrared or nuclear testi ng condition, but other conditions are evaluated by an expert. Complete is most reliable for base scanning; acceptable and there is no wet insu- replacement may be required. other methods can be used for de- lation or leaks, flashing should be re- tailed verification. paired immediately to keep water This article is reprinted from the July from entering the roof system. 9, 1987 issue of PLANI ENC/NFER- Once a roofing system has lf the roof leaks, wet insulation lNG, with permission of the author been properly Ínstalled, it must be replaced. lf the wetness is and the publishers. confined to a small area, or if a large must be inspected and maintained. When inspectíons Wílliam M. Easterly (Retìred), are regular, small defects can Project Manager of Corporate repaired Facil ities, Planni ng, & be detected and Development, Rexnord, before they turn ìnto major Brookfield, Wl failures. lournal is a publication of Hoffmann Destructive testing typically in- Arch itects, special ists i n investi gative volves cutting into the roofing system and rehabil itative architecture/engi- for physical analysis of insulation, neering, including the analysis and barrier, and decking. The extent of solution of roofing, masonry, glazed water damage, deck deterioration, SPlit curtain wall and structural problems. are located at 3074 Whit- and structural dead load capacities wet area is confined to one location, Our offices ney Avenue, Hamden, CT 06518 can be determined from the examina- the insulation can be replaced in Phone (203) 28l -4440 and 1 Bl 6 Sher- tion. lt is a good idea to use independ- those spots only. man Street, Hollywood, FL 33020, ent service compan ies for testing roof lf the flashings are water tight and (30s)-922-1 205. systems rather than those associated the roof shows signs of degradation with roofing manufacturers or con- from previous repairs, or if the roof We welcome contributions to HNJ tractors. leaks and the flashings are in bad from our clients and friends. Please condition, the insulation is probably send news and technical information EVATUATION wet and must be replaced. to Peter Borgemeister, Editor, lf there are no leaks, the condition lf flashings are open and ridging Hoffmann Architects/Journal at the of the flashing system is good, and the and splits are in evidence, the roofing Hamden address. Address changes and additions to the mailing Iist should overal I appearance ofthe roof reveals system may need complete replace- be sent to Patricia Spiegelhalter ín no serious problems, proper mainte- ment. The stresses that cause spl itting Hamden. nance will allow continued good and subsequent damage usually can-

3 When ls lt Safe To Re-Cover An Existing Roof? by Karen L. Warseck

Most roofing systems manufactur- ing system can do a lot worse than premium cost. ers state in their sales literature that void a warranty. lf the deck is steel, Unless the existing roof is their product can be used, in some wood, wood fiber or gypsum, the removed, there is virtually no way of cases, to re-cover an existing roof. At moisture can cause potential life knowing the condition of the deck first look, the advantages appear safety problems due to rusting underneath it. Simply looking atthe overwhelming. The owner saves the through a steel deck or rotting of deck from below may not uncover cost of tear-off. The noise, dirt and wood or wood fiber. the hazards - decks deteriorate from inconvenience of tear-off are elimi- Cypsum decks will turn into water coming in from above, nol powder below. Think of the potential liability nated. The building 'emains some- when constantly exposed to what watertight during the installing moisture. Composite decks of gyp- if someone should fall through a dete- of the new roof. Normal operations riorated deck! are less disturbed by the roofing work. INHERITED MOISTURE Allthese are very compelling argu- PROBTEMS ments. ln addition to life safety hazards However, the realities of the situ- due to deck deterioration, moisture i n ation require careful consideration. the existing roof can cause problems First of all, the reason roof replace- with the new system. The new roof ment is under consideration is be- may appear to be leaking, when in Ponding and Heavy Blistering cause the existing system leaks. fact, the moisture is trapped in the old Almost never is a roof considered for sum mechanically fastened to steel one and finding its way through the major work simply because it has ex- are especially susceptible to moisture deck. lmpervious re-cover mem- ceeded its projected life span. More damage. The gypsum will deterio- branes such as built-up, modified likely, it has leaked and been patched rate when wet, the fasteners corrode, bitumen or coated polyurethane on many occasions over a long pe- and, because the steel deck in these foam will blister if installed over a riod of time. This means that water systems is extremely thin, it will rust moisture-laden substrate. These blis- has entered the existing system and is through that much more quickly. ters are easily broken by foot traffic, probably being retained in the insula- Even concrete decks, although allowing water into the new roof. tion. less susceptible to damage, are not Because adhesion of roofing mate- Thus, in a typical re-roofing situ- immune. Since wet insulation has no rials is adversely affected by damp- ation, there are various degrees of wet insulating value, the concrete deck ness, existing moisture may prevent insulation under a membrane of below can be subjected to freezel any adhered system from bonding to dubious integrity. Logically, this is thaw damage. Any cracks in the the substrate. The weight of the water not the best substrate in which to concrete can let water into the rein- trapped in the existing insulation may attach a new and expensive roof. forcing steel, causing corrosion and also cause the new re-cover to ex- Furthermore, manufacturers will possibly spalling the deck. Light- ceed the design load of the roof as- not warranty an installation over a weight insulating concrete fill will sembly, eventual ly causi ng structural wet or faulty substrate. Unfortu- deteriorate rapidly under freezel failure. nately, "faulty" is usually not defined thaw cycling, with the result that it Re-cover recommendations gen- until warranty repairs are required. becomes the consistency of beach erally require either removal of gravel sand. Because there is no way of on a built-up roof and installation of a LIFE SAFETY PROBLEMS fastening to such deteriorated fill, re-cover board or insulation over the The water entrapped in the exist- complete removal is required, at a existing surface' :#"'."t*i:l;

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Aggregate (1 ) Crushed stone, crushed slag, or water-worn and sulfur dioxide. They are used in both vulcanized and gravel used- for surfacing a built-up roof. (2) Any granular nonvulcanized forms. Most membranes based on CSPE are mineral material. nonvulcanized. ASTM designation for this polymer is CSM. Air l-ance A device used to telt, in the field, the integrity of Cigar A long tubular wrinkle in a single ply membrane. field seams- in plastic sheeting. lt consists of a wand or tube Coal Tar- A dark brown to black cementitious material which compressed air is blown. produced- by the destructive distillation of coal. Alligatoring The cracking of the surfacing bitumen on a Coated Fabric Fabrics which have been impregnated and/ builrup roof,- producing a pattern of cracks símilar to an or coated with- a plastic material in the form of a solution, alligators hide; the cracks may not extend through the dispersion, hotmelt, or powder. The term also applies to surfacing bitumen. materials resulting from the application of a preformed film Asphalt A dark brown to black cementitious material in to a fabric by means of calendering. which -the predominating constituents are bitumens which Coated Sheet (Or Felt) (1) An asphalt felt that has been occur in nature or are obtained in petroleum processing. coated on both- sides with harder, more viscous asphalt. (2) Backnailing The practice of blind-nailing roofing felts to a A glass fiber felt that has been simultaneously impregnated substrate in- addition to hot-mopping to prevent slippage. and coated with asphalt on both sides. Ballast Paving blocks or rounded river bottom stones used Cold Patch To repair a roof leak by using prepared roofing to hold- down a loose laid or IRMA roof. or membrane- and plastic cement. Base Flashing A flashing used to cover the end of a Cold-Process Roofing A continuous, semiflexible mem- membrane. - brane consisting of plies- of felts, mats, or fabrics laminated Bitumen (1) A class of amorphous, black or dark-colored, on a roof with alternate layers of roof cement and surfaced (solid, semi-solid,- or viscous) cementitious substances, with a cold-applied coating. natural or manufactured, composed principally of high Collar Metal flashing for a vent pipe. molecular weight hydro-carbons, soluble in carbon Condensation- The conversion of water vapor or other gas to disulfide, and found in asphalts, tars, pitches, and asphal- liquid as the temperature- drops or atmospheric pressure rises. tites. (2) A generic term used to denote any material com Coping A covering on top of a wall exposed to the posed principally of bitumen. (3) ln the roofing industry. weather,- usually sloped to carry off water. there are two basic bitumens: asphalt and coal-tar pitch. Counterflashing Formed metal or elastomeric sheeting , Before application, they are either; (a) heated to a liquid secured on or into- a wall, curb, pipe, roof-top unit, or other state; (b) dissolved in a solvent; or (c) emulsified. surface, to cover and protect the upper edge of a base Blister An enclosed pocket of air mixed with water vapor, flashing and its associated fasteners. trapped- between layers of felt, foam or other impermeable Creep The dimensional change with time of a material layers. under- load, following the initial instantaneous elastic Brooming Embedding a ply by using a broom to smooth it deformation. Creep at room temperature is sometimes out and ensure- contact with the adhesive under the ply. called cold flow. BTU (British Thermal Unit) The heat energy required to Cricket A small false roof used to throw off water from raise- the temperature of one (1 ) pound of water one (1) behind- an obstacle such as a chimney. degree Farenheit. Cure To change the properties of a polymeric system into Built-Up Roofing (BUR) A continuous, semiflexible a more- stable, usable condition by the use of heat, radia- membrane consisting- of plies of saturated felts, coated felts, tion, or reaction with chemical additives. fabrics or mats assembled in place with alternate layers of Cutback Solvent-thinned bitumen used in cold-process bitumen, and surfaced with mineral aggregate, bituminuous roofing -adhesives, flashing cements, and roof coatings. material, or a granule surfaced sheet. Cutoff A detail designed to prevent lateral water move- Calender A precision machine used preparation - - for of ment into the insulation where the membrane terminates at highly accurqte continuous sheeting or plying up of rubber the end of a day's work, or used to isolate sections of the compounds and frictioning or coating of fabric with rubber roofing system. lt is usually removed before the continu- or plastic compounds. ation of the work. Cap Sheet - A granule-surfaced coated felt used as the top Dead Level Absolutely horizontal, or zero slope. ply of a built-up roofing membrane. Dead Loads - Non-moving rooftop loads, such as mechanical Cant S r flashings to modify equipment,- air conditioning units, and the roof deck itself. thea gorwaterproofing Deck The structural surface to which the roofing or water- mem proofing- system (including insulation) is applied. Capillarity - The action by which the surface of a liquid Degradation A deleterious change in the chemical (where it is in contact with a solid) is elevated or depressed, structure, physical- properties, or appearance of a plastic. depending upon the relative attract¡on of the molecules of Delamination Separation of the plies in a membrane of the liquid for each other and for those of the solid. separation of- insulation layers after lamination. Caulking A composition of vehicle and pigmen! used at Drain A device that allows for the flow of water from a ambient -temperatures for filling joints, that remains plastic roof area.- for an extended time after applications. Eof Chlorinated Polyethylene (CPE) Family of polymers oll produced by chemical reaction- of chlorine on the linear backbone chain of polyethylene. CPE can be vulcanized EL',- but is usually used in a nonvulcanized form. Chlorosulfonated Polyethylene - (CSPE) Family of polymers Embedment The process of pressing a felt, aggregate, that are produced by polyethylene reacting with chlorine fabric mat or- panel uniformly and completely iñto hot

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bitumen or adhesive to ensure intimate contact at all points. form a continuous membrane. Such systems normally do Envelope A continuous edge seal formed by extending one not incorporate reinforcement. ply of felt- beyond the edge of the assembly. After other Fully Adhered An application technique where the plies or insulation are in place, the extended ply is turned mémbrane is -completely attached to the substrate by means back and adhered. of adhesive or bitumen. EPDM A synthetic rubber based in ethylene, propylene, Glass Felt Class fibers bonded into a sheet with resin and and a- small amount of non-conjugated diene to provide suitable for- impregnation in the manufacture of bituminous sites for vulcanization. EPDM features excellent heat, waterproofing, roofing membranes, and shingles. ozone and weathering resistance, and low temperature Glaze Coat (1 ) The top layer of asphalt in a smooth- flexibility. - Expansion foint A structural separation between two ofa b-uilding elements- ihat allows free movement between the ,of elements without damage to the roofing or waterproofing system. are Exposure (1) The transverse dimension of a roofing embedded in the coating. element -not overlapped by an adjacent element in any than roofing system. The exposure of any ply in a membrane may be computed by dividing the felt width minus 51mm (2 in.) by the number of shingled plies; thus, the exposure of a he 914mm (36 in.) wide felt in a shingled, four-ply membrane should be 216mm (81/2in.). (2) The time during which a roofing. portion of a roofing element is exposed to the weather. Gutter Metal or wood trough at edge of roof to drain rain Fabric Reinforcement A 'fabric, scrim, etc., used to add water.- structural strength to -a two or more ply polymeric sheet. Headl ance, measured at 90 degrees Such sheeting is referred to as "supported." to th a shingle or felt as applied to a Factory Mutual (FM) An organization which classified roof rool the shingle or felt, to the assemblies for -their five characteristics and wind-uplift nearest exposed surface. resistance for insurance companies in the United States. Heat Seaming The process of joining two or more thermoplastic -films or sheets by heating areas in contact with each other to the temperature at which fusion occurs. ln dielectric seaming, the heat is induced within films by means of radio frequency waves. Holiday An area where a liquid-applied material is mrssrng.- Hydroscopic Attracting, absorbing, and retaining atmospheric moisture.- IRMA (lnverted Roof Membrane Assembly) A roofing system- where the membrane is applied first then the insulation is laid over it and ballasted. Leader Another term for down-spout. tift The- layer of polyurethane foam resulting from a single Fishmouth ligator pass- of the spray gun, normally ranging Írom'f ,to'{ inch Factory Square 108 ft.' (1 0 MÐ. in thickness. Fallback A reduction- in bitumen softening point, some Mechanically Fastened An application technique where times caused- by refluxing or overheating in a relatively the membrane is fastened- to the building by penetrating closed container. fasteners which are then sealed, or by non-penetrating Felt A flexible sheet manufactured by the interlocking of fasteners such as disks or tracks which are attached to the fibers- through a combination of mechanical work, moisture, building under the membrane. and heat, without spinning, weaving, or knitting. Roofing Membrane Applies to a continuous sheet of material felts are manufactured from vegetable fibers (organic felts), whether it- is prefabricated as a flexibly polymeric sheeting asbestos fibers (asbestos felts) or glass fibers (glass-fiber felts). or is sprayed or coated in the field. Fishmouth A half-cylindrical or half-conical opening Metal Flashing Frequently used as through-wall, cap- or formed by- an edge wr a roofing felt. counter-flashing.- Flashing The system edges at walls, Mineral-Surfaced Sheet A felt that is coated on one or expaniion- joints, drai er places both sides with asphalt -and surfaced with mineral granules. where the membrane is interrupted or terminated. Base Mole Run A meandering ridge in a membrane not flashing covers the edges of the membrane. Cap or counter- associated- with insulation or deck joints. flashing shields the upper edges of the base flashing. Mop-and-Flop A proçedure in which roofing elements Flashing Cement A trowelable mixture of cutback bitumen (insulation 6oards,- felt plies, cap sheets, etc.) are ¡nitially and mineral stabilizers- including asbestos or other inorganic placed upside down adjacent to their ultimate locations, are fibers. coated with adhesive, and are then turned over and ad Flood Coat The top layer of bitumen used to hold the ag- hered to the substrate. gregate on -an aggregate-surfaced, built-up roofing membrane. Mopping The application of hot bitumen with a.mop or Fluid-Applied Elastomer An elastomeric material, fluid at mêèhanical- applicator to the substrate or to the plies of a - (1) ambieni temperature, that dries or cures after application to built-up roof. There are four types of mopping: solíd -

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A continuous coating; (2) spot- bitumen is applied in roof membrane has at least four plies of felt at any vertical roughly circular areas, generally about 460mm (1 I in.) in cross section cut through the membrane. diameter, leaving a grid of unmopped, perpendíÒular areas; Point of Felt Weight in pounds per 480 square feet of dry (3) strip- bitumen is applied in parallel bands, generally felt. Example:- 50 point dry felt weighs 50 pounds per 480 200mm (8 in.) wide and 300mm (12 in.) aparÇ (4) sprinkle square feet. bitumen is shaken onto the substrate from a broom or Polyester Fiber Ceneric name for a manufactured fiber -mop in a random pattern. used for fabric- reinforcement. Neoprene (Polychloroprene) Ceneric name for a synthetic rubber based- primarily on chloroprene. Vulcanized generally with metal oxide. Resistant to ozone and aging and to some oils. NineÇ-Pound A prepared roll roofing with a granule- surfaced exposure- that has a mass of approximately 44OO glm, (90 lb./l08 ft..). Nylon Used as a scrim in fabric reinforced sheeting. Orange- Peel A finished polyurethane foam surface very moderately -textured approximating the appearance of an orange peel. Overhang portion of roofing extending beyond the deck. -That Overspray Minute droplets of foaming mixture that Rusting Perforations become windborne,- foaming in transit and becoming deposited to other than the intended surface. Polyisobuty of P extends above the roof line. isobutylen liquid to a rubbe n ' ::ffi[:',',*yJ:;liff.n molecular are prefastened to the substrate. (PVC) Polyvinyl Chloride A synthetic thermoplastic , Penetration The measurement of the hardness or plasticity polymer prepared -from vinylchloride. PVC can be com- expressed as- the distance that a standard needle vertically pounded into flexible and rigid forms through the use of penetrates a sample of the material under known conditions plasticizers, stabilizers, filler, and other modifiers, rigid of loading, time, and temperature. forms used in pipes, flexible forms used in manufacture of Permeability (1) The capacity of a porous medíum to sheeting. conduct or transmlt- fluids. (2) The amount of liquid moving Pond A surface which is incompletely drained. through a barrier in a unit time, unit area, and unit pressure - gradient not normalized for but directly related to thickness. Permeance The rate of water vapor transmission per unit area at a steady- state through a membrane or assembly, expressed ín -in. Hg). Phased Applic of applying the felt plies of a built-up two or more operations, Puncture Resistance Extent to which a material is able to separated by a delay normally of at least one (1) day (not a - recommended practice). Picture Framing A rectangular pattern of ridges in a membrane over- insulation or deck joints. Also called photo-graphing. Pinholes Minute cylindrical holes in the surface of urethane- foam resulting from irregular expansion. Not plastic to improve its strength, stiffness and impact resistance. Reinforcements are usually long fibers of glasô, sisal, cotton, etc. in woven or non-woven form. To be effective, the reinforcing material must form a strong adhesive bond with the resin. R two opposite sides

R nt of a membrane,

Rise The direction of volumetric growth in the polyurethane- foaming process.

shaped by flow. P ticizer is a material, incorporated in a to increase its ease of workability, sibility. P a roofing membrane; four-ply built-up

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after removal of a deforming force. Refers to both synthetic make the cell structure uniform and fine grained. and natural rubber. Also called an elastomer. Tear Strength The maximum force required to tear a Rust A rust colored discoloration of foam surface resulting material, the -force acting substantially parallel to the major from- exposure to air and ultra-violet. Saddle A ridge in the roof deck, whose top divides the elevation- of the roof so that water will be diverted to the drainage heads. Scrim A woven, open mesh reinforcing fabric made from continuous- filament yarn. Used in the reinforcement of polymeric sheeting. Scupper A device that allows for the flow of water from a and protect the edge of a membrane or flashing. rooÍ area- through a wall or other perimeter obstruction. Thermal Resistance (R) An index of material's resistance to Seam Strength Strength of a seam of material measured heat flow; it is the reciprocal- of thermal conductivity (k) or either in shear- or peel modes. Strength of the seams is thermal conductance (C). The formula for thermal resis- reported either in absolute units (e,9., pounds per inch of tance is: width) or as a percent of the strength of the sheeting. Shingling The procedures of laying parallel felts so that R = l/C or R = l/k or R = thickness in inches/k . longituðinal- edge of each felt overlaps the adjacent felt. Normally, felts are shingled on a slope so that the water Thermal lnsulation A material applied to reduce the flow flows over rather than against each lap. of heat. - Silicone A two-part, chemically cured, liquid-applied Thermal Shock The stress-producing phenomenon material- which will cure to a silicone rubber membrane. resulting from -sudden temperature drops in a roof mem- Slippage Relative lateral movement of adjacent compo- brane when, for example, a rain shower follows brilliant n-ehtiof- a built-up membrane. lt occurs mainly in roofing sunshine. membranes on a slope, sometimes exposing the lower plies Thermoplastic Capable of being repeatedly softened by or even the base sheet to the weather. increase of temperature- and hardened by decrease in Slope The tangent of the angle between the roof surface pl and the- horizontal. lt is measured in inches per foot. The Asphalt Roofing Manufacturers Association (ARMA) ranks rlr slope as follows: in ts Level Slope Up to '/, inch per foot cavities, positioned to direct any water within the wall to Low Slope '/, inch per foot to 1 '/,inches per foot the exterior. Steep Slope Over 1 '/, inches per foot Tree Bark An unacceptable foam surface very heavily tex- Smooth A finished polyurethane foam surface with tured in ridges- approximating the appearance of the bark virtually- no texture approximating the appearance of deep, of an oak tree. freshly fallen snow. Ultimate Elongation The elongation of a stretch specimen Smooth Surfaced Roof A built-up roof without mineral at the time oi break.- Usually reported as percent of the aggregate surfacing. - original length. Also called elongation at break. Softening Point The temperature at which a bitumen Underwriters' Laboratories A non-profit organization becomes soft enough- to flow as determined by and arbi- maintained in the interest of- insurance companies to deter- trary, closely defined method. mine fire resistance of various materials. Softening Point Drift A change in the softening point Valley The place of meeting of two slopes of a roof, forming during storage or application.- a depression- that carries water to an outlet or drainage Split A membrane tear resulting from tensile stress. head. S(uare- A term used by roofers to indicate an amount of Vapor Migration The movement of water vapor from a roof area- equal to 100 square feet (92.2m'). Sufficient region oÍ high vapor- pressure to a region of lower vapor roofing material to cover 100 square feet of roof area. pressure. Stack Vent A vertical outlet in a built-up róofing system to Vent An opening designed to convey water or other gas relieve the- pressure exerted by water vapor between the from- inside a building or a building component to the roofing membrane and the vapor retarder or deck. atmosphere. Strawberry A small bubble or blister in the flood coating ma nding up of a gravel-surfaced- membrane. Stress Plate A flat disk used at the head of a fastener to fin oderately resist downward- punching through a membrane or insulation. ng surface of a Stripping (Strip Flashing) (1) The technique of sealing a cracker without holes. joint between- metal and built-up membrane with one or Vulcanization An irreversible process duríng which a two plies of felt or fabric and hot- or cold-applied bitumen. rubber compound,- through a change in its chemical (2) The technique of taping joints between insulation boards structure (e.g., crosslinking), become less plastic and more or deck panels. resistant to swelling by organic liquids, and elastic proper Substrate The surface upon which the roofing or water ties are conferred - placed (structural deck or insulation). Loads that are added to existing Glossary is published by Hoffmann Architects, specialists ¡n investigative S and rehabilitative architecture/engìneering. Our offices are located at 3074 large stack of insulation boards Whitney Avenue, Hamden, CT 065 1 I Phone (203) 281 -4440 and I 81 6 placed on top of a structural steel deck. Sherman Strcet, Hollywood, FL 33020, (305)-922-1 205. Surfectants - Chemical additives used in foam systems to

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Roof Re-Cover continued from page 4

brane or insulation are to be directly can cause more problems than it further because the various types of

adhered to the substrate, incomplete helps solve. By doing any tear-oÍf , moisture detection equipment do not removal of gravel, or dirt left on the the building interior is stil/exposed to work equally well on all types of substrate, can interfere with adhesion the weather, noise, dirt and cost of roofing. For instance, no detection and increase the opportunity for a tear-off. Thus, the original reasons for system works well on a Protected blow-off. not contemplating tear-off are ne- Roof Membrane Assembly (PRMA) ln most cases, however, the new gated. Another potential problem is roof or lightweight insulating con- insulation or re-cover board is me- that a clear determination of what crete. Capacitance meters have little chanically fastened to the substrate. should selectively be torn off often or no value in evaluating ethylene Mechanical fasteners, piercing can not be established. The reason propylene diene monomer (EPDM) through wet insulation, will eventu- membranes or extruded polystyrene ally rust. Even if they are specially and sprayed-on urethane foam insu- coated to resist rusting, steel deck at At fÍrst look, the advantages lations. Nuclear meters do not re- the fastener holes is not. As the steel spond on either of those, or with seem overwhelming. But around the fasteners rusts away, the if foamed glass. They also will give hole enlarges. Whether it is the deck the issue is not carefully anomalous readings near wal ls, para- or the fastener that rusts, the fasteners thought out and the ramifíca- pets or thick membranes. lnfrared will no longer be held in place by the tions thoroughly considered, scanners will give false or misleading deck. As a result, they can easily be the situatÍon can be deadly. readings over extruded polystyrene, pulled out, thereby vastly increasing all concrete, and foamed glass insula- the opportunity of a roof blow-off. tions. lnfrared scanners cannot be ln any case, fasteners penetrating used on ballasted systems (unless the the substrate on a re-cover provide a for this is that there is no commonly rock is removed) and may give channel for entrapped moisture accepted definition of what is meant anomalous results in areas that have through the deck into the occupied by "weI" insulation. A contractor, for been shaded from the sun all day. So, space. example, may remove only what is even if the roof is tested to evaluate With all the problems that can damp to the touch. lf the new roof result from wet insulation, logic dic- fails shortly thereafter, is the contrac- tatesthe removal of the moisturefrom tor wrong? Not necessarily. He or the existing substrate. One popular she may be using a different standard way is to attempt to dry out the insu- of "wetness". lation by the'instal lation of roof vents. Obviously, completely saturated Unfortunately, roof vents do virtually materials must go. But what about nothing to remove trapped water that which is merely damp to touch, from saturated insu lation. Wh ile they or that which feels dry but moisture don't dry wet insulation, they may be readings indicate to be damp? How helpful (and this has not been proven) do you determine where damp ínsu- in relieving vapor pressure in damp lation stops and dry insulation be- Ridges insulation. lf the moisture is trapped gins? Part of the confusion results be- insulation conditions, there are no between plies in a built-up roof, or in cause different insulation materials guarantees of accu racy. open cells in a closed cell insulation, have different tolerances to moisture, lf a partial tear-off is done, you vents will do no good at all because and different membrane systems also must consider also that, unless the they rely on vapor migration to re- have different tolerances to moisture insulation heightof theexisting roof is lieve pressure. content. What may be "wet" in one matched exactly by the new insula- situation may not be a problem in tion, the difference in elevation may SEI.ECTIVE TEAR.OFF another. cause ponding (standing water) in Another way is to selectively tear The problem of determining low areas or near high spots where off parts of the roof. However, this where to stop ripping is complicated the higher areas interfere with drain-

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age. ln addition to causing premature flowing over the tops of the flashings on roof assemblies, and, in order to breakdown of most membranes, and causing leaks. qualify for the listing, the roof must standing water at best encour- ln addition, extra long fasteners contain only the materials listed. ages leaks even- at minor- flaws. At will be needed to fasten the new insu- There are no listings for re-cover as- worst, the extra weight of the pond lation to the deck. These long fasten- semblies. Code violations may also can overload the structural system ers are prone to bending and metal occur, as some of the model building and cause a roof collapse. fatigue. lf this happens, the fastener codes require rated roofs in fire dis- can break off and puncture the tricts. membrane; or, if enough fasteners The question becomes, then: break, allow the roof to blow off. To When is it safe to re-cover a roof at all? combat this problem, extra large di- lf the issue is notcarefullythoughtout and all of the ramifications are not fully considered, the situation can be deadly. Ask yourself these questions: Existing moisture could pos- ls the roof generally in good condi- sibly prevent any adhered tion? Have the leaks in the roof been system from bonding to the localized and of short duration ? ls original substrate. the roof youngerthan its expected life, span? Will the structural system support the extra load of the new roofing system? Has the condition of ameter fasteners must be used but Existing Moisture the insulation been tested and veri- they cost a premium price. - fied? ls this building located in a fire PROBTEMS ASSOCIATED WITH Careful selection of roofing sys- districtthat requ i res a rated roof? ls an ADDING TAYERS OF tems is important in general, and FM or UL listing required? lf you can't INSULATION careful selection of a re-cover mem- answer any of these with a "yes" , or iÍ Simply adding insulation layers on brane and insulation is essential. you don't know for certain, consult a top of the existing roof can cause Severe failures can result when the building diagnostics specialist. He or other problems. Most manufacturers specified material for the new insula- she can help you determine which require a minimum six-inch vertical tion or the re-cover membrane are way to go. flashing leg to warranty the roof. chemically incompatible with the When the roof elevation is raised, existing materials on the roof. Also, reglets may become too low above the weight of the new materials to be the finished roof heightto provide this added must be carefully calculated. minimum vertical flashing. As a re- An engineering study that includes This article is reprinted with permis- sult, awall may haveto betaken apart all code mandated snow and live sion from the September l9B7 issue and new through-wall flashing in- loads must also be completed to as- of BUILDINC OPERATTNG MAN- stalled above the higher roof flashing. sure thatthe added weightof the new AGEMENT, lf this is not done, water from within roof does not overload the structural the wall will run down behind the capability of the building. roof flashing into the new roof. Mechanical unit curbs, drains, vents IS YOUR ROOF INSURABTE? and other penetrations may have to Finally, your re-covered roof may be raised due to the change in not be insurable. lf your insurer re- Karen L. Warseck is director of the elevation. Minimum flashing heights quires an Underwriters Laboratories Southeastern Region Office of may not be attained if this is not done, (UL) listed or Factory Mutual (FM) Hoffmann Architects. She is an asso- resulting in a non-warrantied roof - rated roof, the re-cover may not ciate member of the American lnsti- and increasing the potential for water qualify. FM and UL ratings are based tute of Architects.

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d servtces

Representative Limestone planting boxes will be The State of Connecticut Depart- repaired; and paving and a canopy ment of Public Works recently en- Projects roof will be replaced at the Warner gaged Hoffmann Architects to pre- Communications Building at pare plans and specifications for the Hoffmann Architects provides a Rockefeller Center in New York City. re-roofing of South Central Commu- wide variety of architectural services Hoffmann Architects is providing the nity College in New.Haven. on existing buildings and buildings architectural direction for this proj- under construction, from pre-mort- ect. The town of North Haven, gage surveys to remedial architec- Con- necticut has retained this ture. A few examples, illustratingthe firm to sur- veythe condition of roofs attheJunior breadth of Hoffmann Architects as- and Senior High signments, include: School buildings.

REMEDIAT FACADE REHABITITATION ARCHITECTURE Remedial Hoffmann Architects prepared Architectural services being provided by Hoffmann Archi- plans and specifications, and will ad- tects on an inn and conference center minister construction, for the reha- in Maryland include: replacementof bilitation of an historic manufactur- waterproof membrane on courtyards ing facility in Bridgeport, Connecti- and walkways; waterproofing cut. The Ceneral Electric Bridgeport of exterior masonry surfaces and founda- Fac i I ity was bu i lt in 1 91 5 for a prede- tion walls; installation a state-of- cessor of Remington Arms Company, of the-art replacement fi specifically for the manufacture of re alarm system throughout the hotel. arms for the Czar of Russia. Ceneral Electric boughtthe plant in 1 922, and has manufactured consumer prod- PTAN REVIEW ucts there ever since, Hoffmann The Weitz is Architects is working on the rehabili- Corporation Hoffmann Architects' tation of balconies that grace the end client for a Plans and Specifications of the many symmetrical bays that Review, and construction distinguish this facility. monitoring services, for Essex Meadows, a life care center being constructed in Essex, Connecti- The limestone walls are being re- cut. pointed and window sealant is being replaced on the 4O-story lnternational Building in New York City. Balconies on this CE facility e being rehabilitated by Hoffmann A hitects. Work is proceeding under the architectural direction of Hoffmann Archi- tects for the Rockefeller Center Man- ROOFTNC PROfECTS agement Corpora-tion. The condition of the roof of the Mid-Manhattan Branch of the New Hoffmann Architects recently York Public Library was investigated conducted a survey of the condition by Hoffmann Architects. Proposals of the exterior walls, courtyard and have also been made to the New York roofs of the Mendenhall Center for Public Library for the general inspec- the Performing Arts at Smith College tion of roof and cellarwallconditions in Northampton, Massachusetts. at two additional branches.

7 staff news

New Staff is pleased to in- Harwood W. loomis. AIA recently Hoffmann Architects 6¡oT(' troduce two new members to the staff: addressed the Hartford chapter of the Na- U fÀ project architect, M. Edds, AIA and tional Association of Corporate Real Es- o &s lames Ð -;'ll senior architect/engineer, Allan H. tate Executives on building envelope m all Gold, AlA, PE. Eads comes to us from problems. He also spoke to the Connecti- cn qe U) Texas where he gained broad experience cut Chapter of the American lnstitute of ôodà residen- Plant Engineers in Danbury, Connecticut c) in commercial, institutional and o gooc tial construction. Cold, also from Texas, about architects' services to facilities Ð o years engineers. Harwood was named to the T o) has twenty-three of comprehensive m I experience as practitioner, educator, Board of Directors of Phenix Society ln- o æ building code official and researcher. ternational, a non-profit group founded I to improve the qualityof the lastone-third oz PROFESSIONAT of life. n ACCOMPTISHMENTS m Theodore F. Babbitt, AIA is on the Russell M. Sanders recently repre- a Board of Directors of The International sented Hoffmann Architects in a presen- C Center. lt is a private, community-based, tation of typical New York City roofing m U) non-profit corporation, formed to ass¡st projects to the winners of the British Flat m-l foreign students, medical personnel at Roofi ng Design Competition. U local hospitals and business trainees with their adjustment to life in the Unlted Marian McFarland is serving as Ex- States. The lnternational Center Resi- ecutive Secretary of the Board of Direc- dence, which houses foreign and Ameri- tors, and President-elect for 1988, of can students, is on historic Prospect Street TEAM, lnc. TEAM is a Community Action in New Haven, Connecticut. Agency which provides services to low income and elderly residents in a 1B- Peter H. Borgemeister, Hon. AlA, has town region. Among the programs are been appointed to the Development Meals-on-Wheels, Headstart pre-school, Committee of the Peabody Museum at and the MANNA elderly nutrition pro- Yale University. 8ram.

AmyC. Kilburn, AIA has also been ap- Susan Hauser, Hoffmann Architects' pointed to a second year of a 3-year term Controller, recently joined the auxiliary as a Director of The Connecticut Society of the Hospital of St. Raphael, a major of Architects/AlA Board of Directors. teaching hospital in New Haven, Con- nect¡cut. Susan is also a Trustee on the town of Hamden Pension Board of Direc- tors. \eiì/

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