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Historic Preservation - Technical Procedures

Spectitle:

Repairing A Wind-Damaged Copper Sheetmetal Roof Ridge & Installing A New Ridge Cap

Procedure code:

0761004R

Source:

Hspg Prepared For Nps - Sero

Division:

Thermal And Moisture Protection

Section:

Sheet Metal Roofing

Last Modified:

02/24/2012

Details:

Repairing A Wind-Damaged Copper Sheetmetal Roof Ridge & Installing A New Ridge Cap



REPAIRING A WIND-DAMAGED COPPER SHEETMETAL ROOF RIDGE AND
INSTALLING A NEW RIDGE CAP


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.


PART 1---GENERAL

1.01 SUMMARY

    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.
         GENERALLY, THIS WORK SHOULD BE ACCOMPLISHED BY A
         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:

         1.   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.
             
         2.   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.

         3.   Be sure the roof is clear of debris and water.

         4.   Do not work on wet snow covered roofs.  Work on
              cleated walkboards.

         5.   Steep roofs:  On roof slopes greater than 4 inches
              rise per foot, special consideration must be given
              to both footing and materials handling.

              a.   Secure chicken ladders or cleats at the top
                   for adequate footing.

              b.   Hang and secure approved safety lines with
                   manila rope

              c.   Carry a limited number of materials so that
                   balance and footing are not impaired.

              d.   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:

         1.   Safety Precautions

         2.   Historic Structures Precautions

         3.   Submittals

         4.   Quality Assurance

         5.   Delivery, Storage and Handling

         6.   Project/Site Conditions

         7.   Sequencing and Scheduling

         8.   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).

1.02 DEFINITIONS

    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:  Steel, aluminum and copper systems
         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:

         1.   Material storage:  Keep uninstalled roof materials
              under cover, dry, free from scratches,
              condensation, and distortion during delivery,
              storage, and handling.

         2.   Historic material to be used as example of original
              construction shall be stored as directed by the
              RHPO.

         3.   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.

1.06 MAINTENANCE

    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.  

         1.   Small pieces of metal with exposed fasteners and
              simple laps may require more maintenance than full-
              length zipped panels.  

         2.   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.


PART 2---PRODUCTS

2.01 MANUFACTURERS

    A.   Follansbee Steel
         State St.
         Follansbee, WV  26037
         800/624-6906

         Standing-seam and batten-seam metal roofing sold through
         distributors.  Free brochure.

    B.   Met-Tile, Inc.
         1745 Monticello Ct.
         Ontario, CA  91761
         714/947-0311

         Tile facsimile metal panel roofing system of galvanized
         metal.  Free literature.

    C.   Metal Sales Mfg. Corp.
         Deer Lake Industrial Park
         P.O. Box 158, Dept. TB
         Orwigsburg, PA  17961
         717/366-2020

         Large, diversified manufacturer of flat metal roofing
         panels, also barrel type tiles.  Free literature.

2.02 MATERIALS

    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

2.03 EQUIPMENT

    A.   Chicken ladder, safety belt or harness.

    B.   Straight snips for cutting straight or slightly curved
         lines in sheet metal 24 gauge or lighter.

    C.   Screwdriver


PART 3---EXECUTION

3.01 EXAMINATION

    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.  

3.02 PREPARATION

    A.   Surface Preparation:

         1.   Carefully examine, measure, and record existing
              sheetmetal patterns at edges, hips, ridges, and
              other special conditions.

         2.   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.  

         3.   For installation of new material, verify the type,
              thickness, weight/gauge prior to installation.

         4.   Prior to installation, remove all oil, dirt, and
              other debris from the surface.  All surfaces shall
              be dry and free from frost.

         5.   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.

    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.

3.04 PROTECTION

    A.   At the end of each work day, provide building protection
         for any exterior roofing element removed during repair.

                             END OF SECTION