By Karl A. Schaak, P.E., RRC INTRODUCTION / \ VARIETY OF PEOPLE MUST ACCESS A ROOF IN ORDER TO FULFILL SPECIFIC DUTIES. THIS / A \ work can consist of making roof repairs, conducting inspections/surveys, or performing repairs/maintenance to / ^ \ rooftop equipment These tasks typically require the individual to walk all or most of a roof A wide variety of / I \__Aroof coverings, various degrees of roof slopes, and changing weather conditions require that people take pre¬ cautions to avoid physical endangerment, damage to the roof covering, or both. GENERAL Upon accessing the roof, whether via ladder, hatch, stairs, or door, an individual should make an immediate peripheral visual survey of the roof to become familiar with the rooftop conditions to identify obstacles, or note possible walkways. The weather often will dictate whether roof access is even viable. During inclement weather such as rain or snow, roof access should be avoided, particularly on steep slope con¬ structions. Even though inclement weather may not be occur¬ ring, the remains and/or residue (i.e., standing water, wet sur¬ faces, snow accumulations, ice buildup, etc.) can also create hazards. Snow, ice, or moisture (even on low-sloped roof assemblies with smooth surfaces, such as single-ply mem¬ brane, modified bitumen sheet membranes, and metal panels), can cause slick surfaces. The occurrence of dew and/or frost early in the day can create similar hazards as those caused by inclement weather Early morning dew and pine needles on metal panel roof system. Other naturally-occurring events that can create dangerous conditions include the accumulation of pine needles and/or leaves on the roof surface. These items, combined with sur¬ face moisture, will most likely create an extremely slick sur¬ face or conceal a potential hazard Saps and other types of oily emissions from trees or other vegetation which may over¬ hang a roof area, can also create slickness on a smooth roof surface by itself or combined with surface moisture. Ponding or standing water on roof surfaces due to inadequate drainage will often lead to silt deposits and/or result in the promotion of algae growth within the area subjected to the ponding water. The source of this water can be either weather-related or due to condensation discharge from HVAC equipment on the roof. These conditions can create treacherous footing, even on low-slope roof constructions with smooth surfaces. Natural elements, including rain, vegetation debris, etc., create extremely dangerous conditions on steep slope roof Grease discharged on surface of metal panel roof system. April 1998 Interface • 21 Detail of proper foot placement on tile roof. coverings. These types of roof coverings include such materi¬ als as shingles, wood shakes, and tile. Walking in these affect¬ ed areas on the roof should be avoided until the condition is rectified (i.e. cleaned, dried, etc). Manmade emissions and/or contaminants such as grease and/or oil from HVAC equipment, exhaust vents, and facility operations (i.e., jet fuel at airports, grease exhaust vents above restaurants) can become deposited on the roof, consequently creating slippery surfaces for smooth-surfaced roof coverings. Other manmade types of elements such as sawdust and metal shavings (both commonly created during the construction/installation of the roof) can also create difficul¬ ties when accessing a roof. ROOF TYPES The type of roof system present will often determine particular precautions to follow when walking on a roof. Tiles Due to the common circular/curved pro¬ file of both clay and concrete tiles, walking on tile roof coverings is difficult. These products typically are not of sufficient strength to resist foot traffic by themselves without sustaining physical damage. The barrel and S-shaped tiles, having a convex profile, will in most instances crack or frac¬ ture when an individual steps on the center portion of the “cover” of the tile. However, if an individual positions the foot perpendic¬ ular to the long dimension of the tile and over the head lap (or overlapped portion of two tiles) and if possible, spanning two cov¬ ers (i.e., heel on one cover and toe on the other cover), damage is less likely to occur. When possible, walking in an internal gutter or open valley that is lined with sheet metal, if present, would also minimize or avoid damage to the tile. Care should also be taken to determine if the tiles are loose-laid or mechanically attached to a nailer or substrate. Foot traffic on loose-laid tile systems may cause unsecured tile(s) to become dislodged, resulting in a potential fall/trip hazard. Loose tiles may also be present in a nailed system. These tiles typically occur along valleys, eaves and/or rakes where underlying sheet metal flashing is installed. Wood Shakes Wood shingles or shakes are typically installed over rela¬ tively close-spaced wood battens and are capable of with¬ standing foot traffic without damage. Damage, however, can occur to weathered wood shingles if the individual traversing the roof is wearing outdoor-type footwear that commonly has relatively large knobby or “lug” soles. Weathered wood shingles/ shakes have a tendency to retain moisture and develop 22 • Interface April 1998 algae/moss growth on the surface of the shingle, particularly in shaded areas of the roof. Algae/moss growth on the surface of wood shingles fosters problematic conditions that can pre¬ vent adequate foot hold. In addition, the ridge cap shingles are typically the least supported of the shingles due to the nature of the installation and are often thinner sections of wood Therefore, walking on the ridge of a wood shingle roof covering should be avoided to prevent resultant damage. Asphaltic Shingles Since shingles are installed over a continuous substrate and are fully supported, foot traffic typically poses very few prob¬ lems. The difficulty with walking on shingle roof construction is typically dependent on the degree of slope present. Slopes of up to 4 inches per linear foot are normally readily accessi¬ ble without the need for additional tools and/or equipment. On slopes greater than 4/12, personnel should consider using specialized tools/equipment (i.e., safety harness, ropes, etc.), in order to maintain proper safety. As with wood shingles, certain footwear (i.e., lug-soled shoes) can cause physical damage (i.e., dislodged granules, fractured mat) to deteriorat¬ ed shingles, particularly organic ones. Again, as typical with most steep roof construction, moisture and/or debris accumu¬ lation on the surface of shingles creates conditions to be avoided or that warrant special care. Slate Similar to asphaltic shingles, slate is installed over a contin¬ uous substrate. The relative hardness of natural slate lends itself to durability to withstand impact. Synthetic slates which are traditionally lighter in weight and thinner in cross-sec¬ tional view than natural slate, however, appear to be some¬ what “brittle” and are more susceptible to damage due to foot traffic. Since slate is rigid, an uneven substrate (joint differen¬ tial in plank/plywood decking) or underlying debris located under the slate, will most likely result in breakage when foot pressure is applied across the field of the slate. Traditionally, slate is installed on greater slopes due to its appearance appeal. Therefore, access on these types of roofs is typically more difficult. In addition, due to the nature of slate, the sur¬ face is relatively quite smooth and slick. Moisture and/or debris on the surface of a slate roof covering makes the roof almost impassable. Because the slates are commonly secured to the substrate with nails that are concealed by the overlying upper slate, someone standing on the roof cannot readily determine the presence or adequacy of the attachment. A per¬ son should approach walking on a slate roof with extreme caution. When slates become detached from the substrate, for whatever reason, they easily slide out from beneath the upper slate, often due merely to gravity. Metal Roofing Metal panel roofing can be installed over either a continu¬ ous substrate or uniformly-spaced (typically five feet on-center) structural steel members. When installed over a continu¬ ous substrate, metal panel roof coverings (structural or archi¬ tectural standing seam roof systems) provide a durable system that is relatively unaffected by foot traffic. When installed over structural steel members, structural standing seam metal Proper foot position on metal tile panels panels also provide a relatively indestructible system in regard to foot traffic. There are several areas of caution in relation to foot traffic on corrugated metal panels that are installed over structural steel members. These panels are light gauge in nature, 24 to 28 gauge, and experience deflection when a load is positioned between support members Although the panels themselves are designed to withstand such deflection, crimp¬ ing of the ribs and separation of side lap sealant may occur under certain point loads (i.e., someone’s foot). Therefore, a person walking on this type of roof system should position their foothold over the structural members (located at fasten¬ ers installed across the width of the panel and in the bottom of the flute). Another area of concern is the presence of translucent cor¬ rugated fiberglass panels. These panels have been used as sky¬ lights in corrugated metal panel systems. After exposure to weathering elements, they characteristically become brittle and unable to withstand minimal, if any, foot traffic. They are often difficult to distinguish from surrounding metal panels with the same profile which have commonly been painted or coated, or due to sun reflection. Care should be taken to identify the presence of these panels and to avoid treading on them. April 1998 Interface • 25 Galvanized and Galvalume® metal panels often come deliv¬ ered to the project site from the manufacturer/supplier with a thin film of oil on the outer surface. This film is applied to the metal sheets for protection,- however, the film can make the panels quite slippery. Built-up Roofing Traditionally, bituminous roof systems are durable roof cov¬ erings that can withstand repeated trafficking. But if certain conditions are present, even these durable systems can become vulnerable. Defects, such as blisters or ridges in the membrane, cause the felts to become raised above the plane of the roof and the underlying substrate. During cold weath¬ er, the bitumen and felts become brittle, and the raised and unsupported portions of the membrane (at the noted defect types) are therefore vulnerable to damage from foot traffic. Although not related to damage or safety, personnel should be aware while walking on a built-up roof membrane during hot weather. Stepping into exposed bitumen that has become softened/molten—particularly coal-tar pitch—will result in bitumen accumulations on the underside of footwear. This soiling of the footwear could result in the contamination of interior building finishes (carpeting, flooring, etc.). This residue is relatively difficult to remove from building finishes without significant effort and possibly resulting in stains. The same logic applies to walking in areas on the roof that were recently repaired utilizing cold process roof cement. Recently-applied mastics and plastic cements remain pliable or in a semi-viscous state for some time after application and can be easily disturbed by foot traffic. Consequently, a foot step in a repaired area can displace the materials and compro¬ mise the integrity of the patch and/or contaminate the indi¬ vidual’s footwear. Miscellaneous Roof Systems Similar to built-up roof systems, blisters and/or raised delaminated areas can be present in spray-applied polyurethane foam (SPUF) roof coverings. SPUF is installed in either single or multiple layers or lifts. A single lift com¬ monly has an overall thickness of one inch. When a blister or delaminated area occurs, the top layer(s) separate(s) or become detached from the underlying substrate. This delami¬ nated portion and relatively thin section of foam becomes unsupported and can easily be damaged by foot impact. A common steep-slope roof covering available today con¬ sists of metal panels that are preformed or stamped to simu¬ late the appearance of wood shingles and/or tiles. Some com¬ mon types of these products include the following: HomeCrest® and Country Cedar® Aluminum Roofing by Alcoa, Decra Tile® and Decra Shake® by Carter Holt Harvey and Gerard Tile® and Gerard Shake® by Gerard Roofing Technologies. These panels are manufactured from light gauge sheet metal (26 gauge, 0.0195 inches thick), either aluminum or galvanized. The panels are available in a variety of sizes, ranging from 40 to 50 inches in length and 12 to 18 inches in width. Since these products are made to mimic the look of ”thick” products, they commonly have a cross-sectional thickness of one inch along the edges and a “hollow” profile in the field of the panel. The panels are Blisters in spray-applied polyurethane foam roof system. installed over wood battens and joined to each other by snap¬ lock types of seams at the ends and sides. Since the panels are installed over battens, the portion of the panel between the battens is unsupported. Foot pressure applied in the field of the panel can cause permanent depressions. An individual should position footholds on the overlapped portions of the panels that are located over the wood battens. This particular portion of the panel is more resistant to foot impact. SAFETY ISSUES An important safety consideration for foot traffic is the avoidance of trip hazards. Rooftop piping, such as electrical conduit, gas, condensate, chill waterlines, etc., is often elevat¬ ed above the roof surface and supported in some way. This piping can often become a series of criss-crossing networks which can easily trip up pedestrians. Other common potential trip hazards at the roof level include flexible cabling (i.e., telecommunications) and guy/support wires, which are typi¬ cally installed for antennas, stacks, or other similar appurte¬ nances extending above the roof surface. These are extremely dangerous, especially during the dusk or night-time hours, as they are difficult to discern due to the relatively thin nature of the material. Traditional walkpads used in the past were made of material which typically did not weather as well as the roof mem¬ brane. Consequently, these walkpads become deteriorated and develop cracks and upwardly curled corners/edges. These can become trip hazards. Other possible trip hazards are standing seam metal roofs. Due to the somewhat odd panel widths (16″ to 18″), a person has to use either shortened or lengthened strides to traverse a typical standing seam metal panel roof. With the height of the standing seam (1″ to 2″), an individual could be caught in mid-stride in the “modified” walking position. Since various types of nails and fasteners are used to con¬ struct the roof or other related components, the extra fasten¬ ers are often discarded or left on the roof surface. The fasten¬ ers, if stepped on in improper footwear, can penetrate the shoe and cause injury. Proper footwear is therefore important. A work type of boot with a durable non-slick sole is the rec¬ ommended type of shoe. 26 • Interface April 1998 SUMMARY Since a roof is commonly accessible and assumed to provide a relatively sound substrate when walked on, the roof cover¬ ing is often treated as an indestructible working surface. However, each person that has to access a roof should take the necessary precautions to prevent inflicting unintentional physical damage to the protective covering for the building. In addition, the safety and well being of the individual are of utmost importance. If existing conditions are present that are considered questionable to an individual in relation to accessibility/ walkability, then the task should be delayed until condi¬ tions improve or are corrected. About The Author Karl A. Schaack received hu velor of science degree in civil engineering from ( lemson University and is a profes¬ sional engineer in the stales of South Carolina, North Carolina, and Texas. He is Vite President of Houston Operations for Price ( onsulting Inc . and is a Registered Roof Consultant through the Roof Consultants Institute Insurance Discounts Mandated for Use of Hail-Resistant Roofs in Texas save, in some parts of Texas traditionally hardest hit by hail, as much as $243 on a typical $716 premium ($80,000 brick veneer home) or $293 on the average $80,000 frame home with a normal premium of $862 The regulations do not currently cover metal roofs, but this issue is being investigated. Of the $1.3 billion in homeowners insurance losses in Texas in 1997, according to a report in the Dallas Morning Neuss, $53 1 million was the result of wind and hailstorms. For more information, contact the Texas Department of Insurance, 1 -800-252-3439, or visit its Website at www.tdi.state.tx.us for a list of discounts. Subscribe for only $50 a year or Else’s Issue of Interface? R ec i p i e n t ’ s X a me _ CompanyMailing Address __ City _ State _ Zip _ O Check enclosed D Bill my credit card: Visa_ MasterCard_ AM Ex_ Expiration Date_ Signature _ If this is a gift subscription, complete the following: ‘l our name .\ddress _ __ _ __ ____ __ _ City __ State _ Zip _ Letter to recipient should read “Compliments of _ ” Complete and send with payment to: RCI • 7424 Chapel Hill Road • Raleigh, XC 27607-5041 800-828-1W2 • 919-859-9742 • Fax: 919-859-1328 eading Someone For the first time, mandatory insurance premium discounts are going into effect for homeowners who install hail-resistant roofs in the state of Texas. The new discounts were ordered recently by Texas Insurance Commissioner Elton Borner and will range by per¬ centage, up to 34 percent, from county to county, according to the history of hail severity from area to area. (Companies whose rates are not regulated by the agency will determine their own discounts). Discounts went into effect for roofs installed on or after Feb. 17 which have passed UL Standard 2218 tests. The com¬ mission reported that hail-resistant roofing materials could cost $600 to $1,000 more than a conventional roof, but could give Interface as a gift to a client. April 1998 Interface • 27
