Supplemental Guidelines for Repairing & Replacing Slate Roofs
- Procedure code:
- Federal Building/US Courthouse, Eau Claire, Wi
- Thermal and Moisture Protection
- Slate Shingles
- Last Modified:
Technical Procedures Disclaimer
Prior to inclusion in GSA’s library of procedures, documents are reviewed by one or more qualified preservation specialists for general consistency with the Secretary of Interior Standards for rehabilitating historic buildings as understood at the time the procedure is added to the library. All specifications require project-specific editing and professional judgement regarding the applicability of a procedure to a particular building, project or location. References to products and suppliers are to serve as a general guideline and do not constitute a federal endorsement or determination that a product or method is the best or most current alternative, remains available, or is compliant with current environmental regulations and safety standards. The library of procedures is intended to serve as a resource, not a substitute, for specification development by a qualified preservation professional.
We’ve reviewed these procedures for general consistency with federal standards for rehabilitating historic buildings and provide them only as a reference. Specifications should only be applied under the guidance of a qualified preservation professional who can assess the applicability of a procedure to a particular building, project or location. References to products and suppliers serve as general guidelines and do not constitute a federal endorsement nor a determination that a product or method is the best alternative or compliant with current environmental regulations and safety standards.
- This procedure provides supplemental guidelines to be used when specifying repair or replacement work on slate roofs. Guidelines for qualification, materials, fabrication and general guidelines for installation are included. This procedure should be used to supplement "Minor Repairs To Slate Roofs" and "Reroofing Using Slate Shingles".
- Product Data: Submit manufacturer's technical product data, installation instructions and recommendations for each type of roofing product required. Include data substantiating that materials comply with requirements. Submit three samples of slates. Submit samples of nails, rag felt and plastic cement.
1.03 QUALITY ASSURANCE
- Manufacturer Qualifications: Provide primary products, produced by a single manufacturer, which has producedthat type product successfully for not less than 3 years. Provide secondary products only as recommended by manufacturer of primary products for use with roofing system specified.
- Installer Qualifications: A single Installer ("Roofer") shall perform the work of this section; and shall be a firm with not less than 5 years of successful experience in installation of slate shingle roofs similar to those required for this project and which is acceptable to or licensed by the manufacturer of primary roofing material.
- Installer Certification: Obtain written certification from manufacturer certifying that installer is approved by manufacturer for installation of specified roofing system. Provide copy of certification to Contracting Officer prior to award of roofing work.
- Installer's Field Supervision: Installer must maintain full-time supervisor/foreperson on jobsite during times that roofing work is in progress. Supervisor must have minimum of 5 years experience in roofing work similar to nature and scope of specified roofing.
- Provide detailed written resume of slate installer's qualifications including at least 5 examples of quality slate installations.
- Pre-Application Roofing Conference: Approximately two weeks prior to scheduled commencement of slate shingleinstallation and associated work, meet at project site with Installer, installer of each component of associated work, other work in and around roofing which must precede or follow roofing work, the Contracting Officer, Government, roofing system manufacturer's representative, and other representatives directly concerned with performance of the work including (where applicable) Government's insurers, test agencies, and governing authorities. Record (Contractor) discussions of conference and decisions and agreements (or disagreements) reached, and furnish copy of record to each party attending. Review foreseeable methods and procedures related to roofing work, including but not necessarily limited to the following:
- Tour representative areas of roofing substrates (decks), inspect and discuss condition of substrate, roof drains, curbs, penetrations and other preparatory work performed by other trades.
- Review roofing system requirements (drawings, specifications and other contract documents).
- Review required submittals, both completed and yet to be completed.
- Review and finalize construction schedule related to roofing work and verify availability of materials, Installer's personnel, equipment and facilities needed to make progress and avoid delays.
- Review required inspection, testing, certifying and materials usage accounting procedures.
- Review weather and forecasted weather conditions, and procedures for coping with unfavorable conditions, including possibility of temporary roofing (if not a mandatory requirement).
1.04 DELIVERY, STORAGE AND HANDLING
- Store in a dry, well ventilated, weather-tight place. Unless protected from weather or other moisture sources, do not leave unused felts on the roof overnight or when roofing work is not in progress. Store rolls of felt and other sheet materials on end on pallets or other raised surface. Handle and store materials or equipment in a manner to avoid significant or permanent deflection ofdeck.
- Felt rolls and shingles which are stored on roofovernight shall be covered with tarpaulins, not plastic. Coverage shall be complete, with tarpaulins extending to bottom to prevent exposure in wind. Material shall be stored in such a manner so as not to exceed 20 PSF loading on roof.
1.05 PROJECT/SITE CONDITIONS
- Weather Condition Limitations: Proceed with roofing work only when existing and forecasted weather conditions willpermit work to be performed in accordance with manufacturer's recommendations and warranty requirements.
- Temporary Protection: Contractor shall be responsible for protection of spaces and contents below roof deck from water leakage. Roof deck shall never be left exposed overnight or during inclement weather.
- The contractor shall be responsible for protection of spaces and contents below roof deck from water leakage. Roof decks or insulation shall never be left exposed overnight or during inclement weather.
- Contractor shall submit, before installation, certification from the producer of slate shingles that the Contractor has undergone training in the application of these shingles by the producer.
- The Contractor shall provide a two-year warranty against leaks, faulty material and workmanship.
- Procedure "Removing Dirt Build-Up From Slate Shingles" contains an extensive list of slate roofing manufacturers for reference.
Reference: ASTM C406/C406M -10 Standard Specification of Roofing Slate
NOTE: See "Minor Repairs To Slate Roofs"or "Re-roofing Using Slate Shingles"for specific materials and equipment required for slate repair and replacement. Other general requirements relating to materials are listed below.
- Material and Workmanship: Slate shall conform to the following requirements:
- Unless otherwise specified, surfaces shall be of reasonably smooth cleavage.
- Slate shall be free from knots or knurls that would lessen the durability or weather tightness of the finished work.
- Unless otherwise specified, slate shall be rectangular, with straight cut edges.
- Unless otherwise specified, corners shall be reasonably full on exposed edges, with no broken corners on covered ends that would diminish the nailing strength or weather tightness.
- Unless otherwise specified, the thickness shall be approximately three-eighth inch.
- Flatness - The maximum bend shall not exceed one- eighth inch in 12 inches.
- Unless otherwise specified, holes shall be machine- punched for 3-inch double lap.
- General Requirements:
- Slate shall be whole and clean. Not more than 2 percent of broken slate will be accepted.
- All slate shall be hard, dense, sound rock, punched for two nails each. No cracked slate shall be used. All exposed corners shall be practically full. No broken corners on covered ends which sacrifice nailing strength or the laying of a water-tight roof will be allowed.
- Detail Requirements:
- Color: To match existing or original and as approved by RHPO.
- Strength: The average modulus of rupture across the grain shall not be lower than 9,000 pounds per square inch.
- Absorption: The maximum absorption shall be - ASTM Grade S1--0.08%
- Acid Resistance: The slate shall, under the acid test, show no softening to an average depth greater than - ASTM Grade S1 -- 0.002 inch.
- Methods of Sampling, Inspection and Tests:
- The inspection of the slate may be made at the discretion of the Government either before or after delivery.
- Samples for test, when required, shall be selected by the Inspector and shall be representative of the material. At least one sample of slate shall be selected from each carload or fraction thereof. Additional samples may be taken for test at any time or place at the discretion of the Government.
- Absorption Test: The specimen shall consist of a square or rectangular slab not less than 4 inches on any side, cut from the slate shingle so that the saw cut is nowhere nearer than 1 inch to the sheared edge.
- Examine substrate surfaces to receive slate shingles and associated work and conditions under which roofing will be installed. Do not proceed with roofing untilunsatisfactory conditions have been corrected in a manner acceptable to Installer.
- Verify that flatness and fastening of wood roof decks are securely fastened with no projecting fasteners and with no adjacent units in excess of 1/16-inch out of plane. Pull out or drive home projecting fasteners.
- Condition of Surfaces: Decks to which roofing system is to be applied shall be sound and dry, clean, smooth and free from projections. Application of roof system components shall not progress when there is ice, frost, surface moisture, or dampness, visible on the roof deck. Deck shall be thoroughly broomed clean, including within flutes.
- Replace any boards of the wood roof deck if shown to be weak structurally, rotted, splintered or broken with treated boards.
- Roof removal is to commence in the center of areas to be removed and to proceed outward to the edge of the areas to be removed.
- Any disintegrating, wet or failed material shall be removed and replaced.
- Removed roofing, insulation, flashing and masonry will be removed from the roof immediately without allowing accumulation of piles of trash. Tossing of any trash,tools or any objects from roof to any areas below, including from one roof level to another, is expressly prohibited.
- Removed materials shall become the property of Contractor and shall be removed from the site. Debris and scrap shall be removed from the work area daily.
- Temporary Roof Installation:
- If adverse weather conditions require protection of exposed deck, install 6 mil polyethylene sheets horizontally, shingling, from top to bottom. Staple and tape all joints and edges.
- Remove temporary roof completely prior to installation of permanent roofing system.