Procedures for Soldering Sheetmetal

CSI Division
Division 5 - Metals
Section
Metal Materials
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.

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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.

PART 1–GENERAL

1.01 SUMMARY

  1. This procedure includes guidance on soldering metal for patching damaged or deteriorated sheet metal roofs and gutters.

  2. See “General Project Guidelines” 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

  1. Solder—metal or metallic alloy of tin and lead used when melted to join metallic surfaces.

1.03 QUALITY ASSURANCE

  1. 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.

PART 2–PRODUCTS

2.01 MATERIALS

NOTE: Chemical products are sometimes sold under a common name. This usually means that the substance is not as pure as the same chemical sold under its chemical name. The grade of purity of common name substances, however, is usually adequate for stain removal work, and these products should be purchased when available, as they tend to be less expensive. Common names are indicated below by an asterisk (*).

  1. Sheet metal to match remainder of roof or gutters

  2. Solder

  3. Soldering flux

  4. Rosin paper

  5. Muriatic acid * (generally available in 18 degree and 20 degree Baume solutions):

    1. A strong corrosive irritating acid.

    2. Other chemical or common names include Chlorhydric acid; Hydrochloric Acid; Hydrogen chloride; Marine acid*; Spirit of salt*; Spirit of sea salt*.

    3. Potential Hazards: TOXIC, CAUSTIC TO FLESH; CORROSIVE TO CONCRETE, STEEL, WOOD OR GLASS, FLAMMABLE.

    4. Available from chemical supply house, drugstore or pharmaceutical supply distributor, or hardware store.

  6. Mineral spirits:

    1. A petroleum distillate that is used especially as a paint or varnish thinner.

    2. Other chemical or common names include Benzine* (not Benzene); Naphtha*; Petroleum spirits*; Solvent naphtha*.

    3. Potential Hazards: TOXIC AND FLAMMABLE.

    4. Safety Precautions:

      1. AVOID REPEATED OR PROLONGED SKIN CONTACT.

      2. ALWAYS wear rubber gloves when handling mineral spirits.

      3. If any chemical is splashed onto the skin, wash immediately with soap and water.

    5. Available from construction specialties distributor, hardware store, paint store, or printer’s supply distributor.

  7. Clean, soft cloths

2.03 EQUIPMENT

  1. Chicken ladder, safety belt or harness

  2. Snips for cutting sheet metal

  3. Soldering copper, soldering iron

  4. Handy tongs for bending the edges of the solder

  5. Metal seamer

  6. Stiff bristle brushes

  7. Metal ruler

  8. Pliers

  9. Weight (bricks)

  10. Clamps

  11. 3-5 lb. propane heater for soldering copper or 200 watt electric soldering iron

  12. Heavy gloves and protective gear

PART 3–EXECUTION

3.01 EXECUTION, INSTALLATION, APPLICATION

NOTE: Use caution in handling flame tools when soldering. The danger of setting the structure on fire is always present.

  1. With chemical paint stripper, remove any paint from the metal surrounding the patch. If there’s any roofing tar, remove it by scraping, followed by scrubbing with kerosene, gasoline, or mineral spirits. CAUTION: THESE SOLVENTS ARE VERY FLAMMABLE

  2. Clean both the roof and the patch piece by scouring with a wire brush or steel wool.

  3. For Copper:
    NOTE: THIS METHOD SHOULD NEVER BE USED TO REPAIR FATIGUE-DAMAGED COPPER SHEETMETAL. SOLDERED PATCHES HAVE A DIFFERENT COEFFICIENT OF EXPANSION THAN THE COPPER AND WILL EVENTUALLY BREAK AWAY. SOLDER IS INHERENTLY A WEAK ALLOY AND SHOULD BE USED ONLY TO CREATE WATERTIGHT JOINTS, NOT WHERE TENSILE OR COMPRESSIVE STRENGTH IS NEEDED. HOWEVER, IT DOES PROVIDE SOME STRENGTH IN CONNECTING SHEETS OF COPPER IN “WEIGHTS” LESS THAN 20 OUNCES.

    1. Apply muriatic acid for 60 seconds to dissolve any oxides.

    2. Rinse with clean, clear water and wipe dry.

    3. Paint on liquid non-corrosive rosin flux (zinc chloride), applying it ONLY where the solder is to go.

    4. Pre-tin the area by heating with a soldering copper and applying a thin coating of solder.

    5. Apply patch and hold in place with heavy weight, or fasten it mechanically with two copper rivets or brass nails. Solder following instructions 4-6 below.

  4. For lead-coated copper, tin, tin plate, terneplate:

    1. Follow instructions for copper, Section 3.01 A. above.

    2. Fasten patches using tinplated cleats or galvanized iron or steel nails.

  5. For galvanized iron or steel:

    1. Clean with muriatic acid as for copper, Section 3.01 A.1. and 2. above.

    2. Because the muriatic acid also acts as the flux, after 60 seconds leave acid in place (DO NOT RINSE), apply patch, and solder following instructions D-F below.

  6. Use bar solder that’s 50% block tin and 50% pig lead and a large soldering copper (typically 1-1/2 lb. or bigger - for galvanized iron, use either a 3-5 lb. propane-heated soldering copper, or a 200 watt electric soldering iron). A home workbench soldering iron won’t transmit enough heat to the roof to get solder to flow under the patch.

  7. Use a well-tinned copper to heat the metal and the solder. Let the solder flow into the seams. If the patch is held in with nails or rivets, be sure the solder covers their heads. Apply the solder using a noncorrosive rosin flux. MAKE SURE THE PATCH DOES NOT MOVE UNTIL AFTER THE SOLDER COOLS; OTHERWISE, THE SOLDER WILL BEGIN TO BREAK. IF THE PATCH MOVES, START OVER.

  8. After the solder has cooled, rinse off all excess flux with clean water and wipe dry. If patch is galvanized, terne, or tinplate, wipe it down with mineral spirits and immediately prime and paint patch to match the remainder of the roof.

 

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Last updated: Jan 3, 2018
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