Repairing Pinch Cracks In Long Copper Gutters
- Procedure code:
- Hspg Prepared For Nps - Sero
- Thermal and Moisture Protection
- Bronze/Copper Gutter/Downspout
- Last Modified:
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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:
- 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. 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:
- 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.
- 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:
- 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.
- 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.
A. Quarter-hard temper copper
B. Stop-end expansion joints
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
- 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.
- 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.
- Keep trees trimmed to prevent branches from scuffing or moving downspouts.
- 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.
- Use quarter-hard temper copper instead of the usual fully annealed material to enhance the strength of the gutter.
- Provide stop-end expansion joints at high points between outlets.
- Join or weather the gutter to the roof sheets and flashing by “sliding” welts or overhanging aprons.
- The permissible length varies with the thickness of the copper used, the width of sole, and the shape of the gutter.
- 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.
- 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.
- Space the dummy welts at a maximum of 4'-3" to provide adequate accommodation for the thermal movement to the gutter lining between drips.