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 has the potential to alter the historic appearance or character of a building. It should only be performed by an experienced professional, and only upon approval from the regional historic preservation officer (RHPO) or designated representative.
This procedure should be performed under the direction of an historical architect or engineer, to decide the most efficient and least destructive manner for executing the work.
A. This procedure includes guidance on repairing a copper sheetmetal roof ridge by removing the damaged section and welting on a new metal capping over timber battens. Note: Generally, this work should be accomplished by an experienced roofing contractor.
B. Wind loading is increased at the ridge of a roof. Cracks in the pans close to the ridge, or cracks on the ridge seam itself, are indications of wind displacement. The cracks occur because the standing seam, typically found at the ridge, lacks the necessary strength to withstand this pressure.
C. Typically a ridge roll is preferred over a standing seam ridge because it provides more strength at the ridge to withstand the forces of wind loads. Therefore, replacement of a standing seam ridge with a ridge roll is often the recommended treatment for wind damage of the ridge.
D. Safety Precautions
- Wear rubber-soled shoes that have non-slip or grid type tread (preferably sneakers with a high top for good ankle support). Avoid wearing loose clothing.
- Wear a safety belt or harness and secure it to a substantial chimney or to a window on the opposite side of the house. Leave only enough slack so you can work comfortably in one area, and adjust the slack as you work on other sections of the roof.
- Be sure the roof is clear of debris and water.
- Do not work on wet or snow covered roofs. Work on cleated walkboards.
- Steep roofs: On roof slopes greater than 4 inches rise per foot, special consideration must be given to both footing and materials handling.
- Secure chicken ladders or cleats at the top for adequate footing.
- Hang and secure approved safety lines with rope of sufficient strength.
- Carry a limited number of materials so that balance and footing are not impaired.
- Use scaffolding, ladders, and working platforms as required to execute the work. Ladders shall not be supported on hanging gutters. These gutters may be distorted which can affect the slope to drain.
E. See 01100-07-S for general project guidelines to be reviewed along with this procedure. These guidelines cover the following sections:
- Safety Precautions
- Historic Structures Precautions
- 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).
A. Bay: a unit of sheet covering as laid between rolls or standing seams.
B. Capping: a copper strip, covering the top of a batten roll, welted to the edges of the sheets which are dressed up the side of the roll.
C. Cleats or clips: strips, cut to lengths to suit roll or seam, placed at intervals and securely fixed to the roof base, the ends being welted in with the edges of the sheets to hold the copper roofing in position.
D. Batten: a shaped timber core against the sides of which the sheet metal is dressed or turned up.
E. Standing seam: a double welted joint formed between the sides of adjacent bays and left standing.
F. Welting: joining copper sheets at their edges by folding together. Welting may by single or double folds, such joints being termed single or double welts respectively.
1.03 SYSTEM DESCRIPTION
A. A firmly secured metal roof lays flat against the decking, and good workmanship ensures that the seams and cross welts are well clipped. There should be no cracks extending along the ridge line, and the ridge seam should be securely fastened.
1.04 QUALITY ASSURANCE
A. Qualifications: Metal roof systems and accessories should be applied by qualified sheet metal mechanics using methods devised or approved by the manufacturer of the metal. Details may vary depending on the properties of the metal, local custom, and architectural effect required.
1.05 DELIVERY, STORAGE, AND HANDLING
A. Storage and Protection:
- Material storage: Keep uninstalled roof materials under cover, dry, free from scratches, condensation, and distortion during delivery, storage, and handling
- Historic material to be used as example of original construction shall be stored as directed by the RHPO.
- Manufacturer’s delivery or job markings on metal, and adhesives for manufacturer's labels shall be either a neutral or slightly acidic material. In no case shall such material be alkaline; any staining of the metal by alkaline materials will be cause for the rejection of the piece.
A. The amount of maintenance required will depend on the kind of roofing used and the exposure hazards. It will also depend on the degree of waterproofing quality and exterior appearance that is acceptable.
- Small pieces of metal with exposed fasteners and simple laps may require more maintenance than full-length zipped panels.
- Factory enamel coatings and concealed fasteners add immeasurably to the appearance and life of a metal roof, and reduce the maintenance cost to the minimum.
B. In addition to scheduled inspections, inspect after each exposure to unusually severe weather conditions such as strong winds, hail, or long continuous rains.
For sources, also check relevant periodicals, web research, and local business directories.
D. Vulcan Supply Corporation
A. Long screws
B. Cleats or clips, metal to be compatible with roofing metal
C. Sheetmetal, same type and weight as existing
D. Rosin Paper
E. Timber Batten
A. Chicken ladder, safety belt or harness.
B. Straight snips for cutting straight or slightly curved lines in sheet metal 24 gauge or lighter.
A. Inspect the ridge for buckling or starcracks near the seam. Inspect the ridge seam to ensure that the seam is securely fastened, welted or clipped.
B. Whenever possible, make inspection from ground or from above if possible.
C. Inspect the underside of the roof deck from the attic to detect leaks.
A. Surface Preparation:
- Carefully examine, measure, and record existing sheetmetal patterns at edges, hips, ridges, and other special conditions.
- Be careful not to damage old metal wall and vent flashings that may be used as a pattern for cutting templates. If metal cap flashings at the chimney and other vertical masonry wall intersections have not deteriorated, bend them up out of the way so that they may be used again. Carefully roof in these areas to avoid damaging reusable base flashing.
- For installation of new material, verify the type, thickness, weight/gauge prior to installation.
- Prior to installation, remove all oil, dirt, and other debris from the surface. All surfaces shall be dry and free from frost.
- Work on only a quantity of roofing which may be repaired on that same day.
3.03 ERECTION, INSTALLATION, APPLICATION
Note: For a detail of this procedure, see the book Practical Building Conservation by John & Nicola Ashurst, English Heritage Technical Handbook. Vol. 4: Metals. New York: Halsted Press, 1988, p. 61.; or check for newer editions of this title.
A. Cut out the entire length of standing seam ridge, undamaged as well as damaged sections.
B. Turn back and fold up the edges of the ridge bays to form upstands which will be welted onto the new ridge cap.
C. Screw new timber battens through the roof deck into the ridge beam or rafters.
D. Nail 2 inch wide clips along the ridge, placed at two per bay. Pass under the ridge roll and turn up on each side, or nail on the side of each section of the roll before fastening.
E. Welt on a new metal capping.
A. At the end of each work day, provide building protection for any exterior roofing element removed during repair.