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Historic Preservation - Technical Procedures

Spectitle:

Repairing Pinch Cracks In Long Copper Gutters

Procedure code:

0760201R

Source:

Hspg Prepared For Nps - Sero

Division:

Thermal And Moisture Protection

Section:

Bronze/Copper Gutter/Downspout

Last Modified:

02/24/2012

Details:

Repairing Pinch Cracks In Long Copper Gutters



REPAIRING PINCH CRACKS IN LONG COPPER GUTTERS


PART 1---GENERAL

1.01 SUMMARY

    A.   This procedure includes guidance on patching pinch cracks
         in copper gutters.  GENERALLY, THIS WORK SHOULD BE
         ACCOMPLISHED BY A EXPERIENCED ROOFING CONTRACTOR.

    B.   Pinch cracks start as a small wrinkle in the angle
         between the bottom of the gutter and the upstand.
         Repeated expansion and contraction cycles enlarge the
         wrinkle and pinch the folds in the copper, causing the
         metal to harden severely and eventually crack.

    C.   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 SUBMITTALS

    A.   Shop Drawings:  Before repairing or replacing gutters,
         prepare a working drawing showing sheet length and width
         between seams.  Prepare typical exposed seam details and
         fastening patterns for guidance.  Submit to RHPO for
         approval.

1.03 DELIVERY, STORAGE AND HANDLING

    A.   Packing and Shipping:  For replaceable material: protect
         gutters and downspouts from damage at all times during
         handling, installation, and operation of the building.

    B.   Acceptance at Site:

         1.   New sheet metal shall be delivered on the job
              carefully packed. Inspect each piece immediately
              before installation, and do not use the pieces
              which have observable edge damage or face
              imperfections.

         2.   Manufacturer's delivery or job markings on the
              sheet metal, and adhesives for manufacturer's
              labels, shall either be a neutral or slightly
              acidic material.  In no case shall such material be
              alkaline; any staining of the sheet metal by
              alkaline materials will be cause for the rejection
              of the piece.

    C.   Storage and Protection:

         1.   Salvaged historic material shall be carefully
              packed and stored under cover and in the building
              away from working or traffic areas. Mark salvaged
              material with the year of removal.

         2.   Keep uninstalled roof gutters and downspouts under
              cover, dry, free from scratches, condensation and
              distortion during delivery, storage and handling.

1.04 PROJECT/SITE CONDITIONS

    A.   Environmental Requirements:  Do not remove gutters from
         structures when rain is forecasted or in progress.


PART 2---PRODUCTS

2.01 MATERIALS

    A.   Quarter-hard temper copper

    B.   Stop-end expansion joints

    C.   Nails

2.02 EQUIPMENT

    A.   Safety belt or harness

    B.   Ladders and scaffolding

    C.   Chicken ladder

    D.   Carpenter's level

    E.   Mason's level

    F.   Sheetmetal snips, tongs and clamps for cutting and
         bending copper


PART 3---EXECUTION

3.01 PREPARATION

    A.   Protection:

         1.   At the end of each work day, provide building
              protection for any exterior gutter element removed
              for repair or replacement, if water penetration is
              possible.

         2.   Landscape work adjacent to or within the ground
              work areas for gutter maintenance shall be
              protected.  Provide plank barriers to protect tree
              trunks.  Tie-up spreading shrubs, and cover as
              necessary, allowing the plants to breathe.  Remove
              the covering and ties at the end of each work day.
              Set scaffold ladder and legs away from plants.
              Pruning requests shall be directed to the RHPO.

         3.   Keep trees trimmed to prevent branches from
              scuffing or moving downspouts.

         4.   Set ladders on an incline whereby the bottom of the
              ladder is approximately 25% of the height from the
              base of the building.  Do not rest ladders on
              gutters.

3.02 ERECTION, INSTALLATION, APPLICATION

    A.   Repairing pinch cracks:  Dressing the wrinkled copper
         flat and soldering a copper patch over the crack may be
         ineffective as the cracking will eventually transfer
         elsewhere.

         1.   Use quarter-hard temper copper instead of the usual
              fully annealed material to enhance the strength of
              the gutter.

         2.   Provide stop-end expansion joints at high points
              between outlets.

         3.   Join or weather the gutter to the roof sheets and
              flashing by "sliding" welts or overhanging aprons.

         4.   The permissible length varies with the thickness of
              the copper used, the width of sole, and the shape
              of the gutter.

         5.   With stop-end expansion joints between every length
              of lining, each section of the gutter must be
              drained separately.  

              NOTE:  Double cross welts have the ability to
              absorb longitudinal expansion movement, but they
              are generally not suitable for this purpose because
              the welts are not sufficiently watertight.
              Furthermore, if ponding water develops and sits in
              contact with the welts for extended periods, water
              may be drawn through the welt.

    B.   To make welts watertight, make a dummy welt.

         1.   Reproduce the folds of a double-lock cross welt in
              a long strip of copper without actually cutting it
              into separate pieces, to form "dummy welts" across
              the gutter.

         2.   Space the dummy welts at a maximum of 4'-3" to
              provide adequate accommodation for the thermal
              movement to the gutter lining between drips.

                             END OF SECTION