Minor Repairs To Asphalt Roll- Roofing Or Built- Up Roofing. Procedure code: 7. SSource: Hspg Prepared For Nps - Sero. Division: Thermal and Moisture Protection. Section: Built- Up Asphalt Roofing System. Last Modified: 0. PART 1- -- GENERAL1. SUMMARYThis procedure includes guidance on making minor repairs to asphalt and built- up roofing membranes. Some problems include open lap joints, blisters, splits, holes, ridges, undulations, wrinkles and cracks. CONTINUAL STRESS ON A RIDGE CAN LEAD TO SPLITTING OF THE MATERIAL. Ridges are firm and do not yield under pressure. They may result from the substrate being uneven before the felt was laid, or from moisture distorting the substrate. Ridging usually occurs over or near joints between boards. The ridges expand as entrapped moisture vaporizes. Ridges become a problem when they interfere with drainage or when the roof begins to leak. Undulations. Unlike ridging, undulations will yield to pressure. Distortions of felts may result from the way the rolls were stored (flat instead of on end), inadequate pressure applied while laying, poor application of bitumen compound, or if entrapped moisture becomes vaporized. Blisters. Blisters will yield to pressure. Blisters begin with the expansion of trapped air and/or moisture pockets and can result from inadequate pressure during laying. Full Membrane Blistering: Usually occurs when no separating layer is provided between the asphalt and the substrate. Inter- layer Blistering. When large blisters result from additional air and water drawn in from outside through the top layer of the felt. Not a common problem, but can result if the 2nd layer does not adhere well to the 1st layer due to the accumulation of dirt or dust.- OR- If a blow develops in the 1st layer, the 2nd layer become thin at that point and allow air and moisture to penetrate between the layers. This can create the potential for a blister to develop. A blister ususally develops under the cap sheet of the membrane. Inter- layer blistering is most common with unsurfaced or mineral surfaced felts on vertical or sloping surfaces. However, high performance membranes can reduce the incidence of this occurring. Top Pitting: NOTE: NO REMEDIAL TREATMENT IS RECOMMENDED, AS THIS TYPE OF BLISTERING SHOULD NOT AFFECT THE EFFICIENCY OF THE WATERPROOFING. Miniature surface blistering of the bitumen coating (especially with BS7. Type 1. E and 2. E mineral- surfaced felts). The blisters may range in size from 1mm to 3mm. Top pitting may be caused by. Trapped air and/or moisture in the manufacture of the material. Oliensis: Incompatibility of the saturating bitumen with the coating bitumen (i. The heat from the bonding bitumen during application can create minor wrinkling or cockles which usually disappears as the material settles. Most common in fiber and asbestos base felts as they tend to expand when their moisture content increases. Cockling is less likely in coated felts especially those with a glass or polyester base. Expert advice on how to repair tile and masonry roofs, including fixing holes and cracks, and tips for replacing broken roof tiles. Portland cement plaster (stucco) is a building facing material consisting of portland cement-based materials and sand, mixed with water to form a workable mixture. Plaster is applied either by hand or machine to exterior and. Blowing. Blows are bubbles that develop on the surface from gas moving through the asphalt. The heat of the asphalt during application causes the air to expand and creates steam by raising the temperature of the moisture. Where there is no separating layer between the asphalt and the substrate. Problems with mineral- surfaced, asphalt roll roofing and built- up roofing membranes are usually related to sun exposure, and excessive moisture. Exposure to the sun may cause the asphalt to dry out, resulting in cracking of the surface, separation of plies, and may eventually require replacement of the entire membrane. The repairs described in this procedure are ONLY temporary. For roofs that are near the end of their useful life, these repairs may provide an extra 3 to 4 years of service, enough time to start planning for a new roof. For roofs that are relatively new, these techniques will provide protection while the cause of the problem is being investigated and more permanent repairs are planned. See 0. 11. 00- 0. S for general project guidelines to be reviewed along with this procedure. These guidelines cover the following sections. Safety Precautions. Historic Structures Precautions. Submittals. Quality Assurance. Delivery, Storage and Handling. Project/Site Conditions. Sequencing and Scheduling. General Protection (Surface and Surrounding)These guidelines should be reviewed prior to performing this procedure and should be followed, when applicable, along with recommendations from the Regional Historic Preservation Officer (RHPO). For additional information on factors contributing to roof deterioration, see 0. S. For guidance on inspecting for sources of flat roof failures, see 0. S. 1. 0. 2 REFERENCESAmerican Society for Testing and Materials (ASTM)www. DEFINITIONSAsphalt- -A dark brown to black semi- solid hydrocarbon obtained from crude petroleum. See ASTM D 3. 12- 7. Asphalt cement- -Trowelable black asphaltic mastic used for flashing and roof repairs. Contains fiber additives to thicken the mixture so that it will not run down vertical surfaces. Also called roofing cement, flashing cement, plastic asphalt cement, plastic cement, roofing tar, bitumen and elastic cement. Bitumen- -A semisolid mixture of complex hydrocarbons derived from coal or petroleum, as coal- tar pitch or asphalt; before application, usually dissolved in a solvent, emulsified, or heated to a liquid state. Built- up roofing- -A continuous roof covering made up of laminations or plies of saturated or coated roofing felts, alternated with layers of asphalt or coal- tar pitch and surfaced with a layer of gravel or slag in a heavy coat of asphalt or coal- tar pitch or finished with a cap sheet; generally used on flat or low- pitched roofs. Bituminous coating- -An asphalt or tar compound used to provide a protective finish for a surface. Coal tar bitumen- -A dark brown to black, semi- solid hydrocarbon, a residue distillation of coal tar. It is used for the construction of low- pitch built- up roofs. It differs from coal tar pitch because of a different volatility. See ASTM D, 4. 50, Type III. Coal tar pitch- -Similar to coal tar bitumen. Used for dead- level or low- slope built- up roofs. See ASTM D 4. 50, Type I. Lap cement- -Thinner than asphalt cement, this is used to make watertight joints at the laps of roll- roofing. Roof restorant- -The restorant penetrates the existing roofing felts and plasticizes the age hardened bitumen to its originally installed state. It will not, however, stop or seal leaks. In addition, a deep coating on the surface provides a weathering surface and a binder for the replacement aggregate. Also called roof coating or roof paint. DELIVERY, STORAGE AND HANDLINGStorage and Protection. Store roof system materials in a dry location. Outside, they should be placed on platforms off the ground or roof deck, covered with waterproof coverings which will not produce condensation. Store roll materials on end to prevent their becoming deformed or damaged. Remove moisture, dirt, snow or ice from roofing bitumens before they are heated. Replace lids on cans of material stored on the job site. Protect water based materials from freezing. PROJECT/SITE CONDITIONSEnvironmental Requirements. It is extremely important that the roof deck be dry at the time roofing operations commence, to avoid later problems with water vapor trapped under the membrane. A deck should not be roofed when rain, snow, or frost is present in or on the deck material. Cold temperatures: Apply roofing materials only when correct bitumen temperatures can be maintained. Keep surface temperature and asphalt thermometers at the work site. Hot temperatures: In hot weather the bitumen will cool slowly, which can lead to sticking, making the membrane susceptible to physical damage from mechanical equipment and foot traffic. Wind: Wind can blow hot materials, mastics and coatings causing damage to surrounding property and making the handling of roll materials difficult. PART 2- -- PRODUCTS2. MATERIALSSand and/or gravel to match existing or historic appearance. Asphalt Roof Felts. BS7. 47 Type 1 fiber base felts - suffer from inter- layer blistering. Type 2 Asbestos base felts - inter- layer blistering is less common. Type 3 Glass fiber felts - Extremely resistant to blistering. Polyester felts - some resistance to blistering. Asphalt cement (also called, among others, flashing cement or roofing cement. Roof Coating (also called roof paint and roof restorant)1- 1/2. Secure covering without the use of adhesive backed tape or nails. Impervious sheeting which produces condensation should not be used. Keep a portable fire extinguisher on hand where work is being done. At the end of each work day provide temporary roofing when existing roof is being opened for repair or replacement. Provide an effective way to divert water runoff away from open roof. Surface Preparation. Sweep exposed felts clean of loose aggregate, dirt and silt with stiff bristled brush or broom. Sweep at least six inches into embedded aggregate in all directions. Clean all roof surfaces, including parapets, copings, and flashings. Sometimes this can be done using a long- handled push broom. In the case of a tar and gravel roof, you may have to cut the gravel off by hand or use a gravel removing machine. Parapet cleaning should include brushing of any efflorescence from the brickwork using stiff, non- metallic bristle brushes. Do not begin repair of flashings until completion of all pointing or resetting of parapet units and repair of coping joints. Go over the entire roof area with roofer's chalk, marking areas where repair work is to be done. EXECUTION, INSTALLATION, APPLICATIONRepairing open lap joints on roll roofing. Force lap cement or asphalt cement under open seam. Weight it down with heavy weight until it is dry. If it pops again, slit wrinkle being careful not to cut sound layers of roofing below. DO NOT ELIMINATE THIS LAST STEP. THE GRAVEL OR SAND REFLECTS SUNLIGHT THUS SLOWING THE DRYING OUT PROCESS. Repairing Small Blisters. 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