Historic Preservation - Technical Procedures
- Procedures For Soldering Sheetmetal
- Procedure code:
- Hspg Prepared For Nps - Sero
- Metal Materials
- Last Modified:
- Procedures For Soldering Sheetmetal
- Last Modified:
PROCEDURES FOR SOLDERING SHEETMETAL
A. This procedure includes guidance on soldering metal for
patching damaged or deteriorated sheetmetal roofs and
B. 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
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).
A. Solder--metal or metallic alloy of tin and lead used when
melted to join metallic surfaces.
1.03 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
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 (*).
A. Sheetmetal to match remainder of roof or gutters
C. Soldering flux
D. Rosin paper
E. 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, CORROSIVE TO FLESH;
CORROSIVE TO CONCRETE, STEEL, WOOD OR GLASS,
4. Available from chemical supply house, drugstore or
pharmaceutical supply distributor, or hardware
F. 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*;
3. Potential Hazards: TOXIC AND FLAMMABLE.
4. Safety Precautions:
a. AVOID REPEATED OR PROLONGED SKIN CONTACT.
b. ALWAYS wear rubber gloves when handling
c. 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.
G. Clean, soft cloths
A. Chicken ladder, safety belt or harness
B. Snips for cutting sheet metal
C. Soldering copper, soldering iron
D. Handy tongs for bending the edges of the solder
E. Metal seamer
F. Stiff bristle brushes
G. Metal ruler
I. Weight (bricks)
K. 3-5 lb. propane heater for soldering copper or 200 watt
electric soldering iron
L. Heavy gloves and protective gear
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.
A. 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
B. Clean both the roof and the patch piece by scouring with
a wire brush or steel wool.
C. 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
1. Apply muriatic acid for 60 seconds to dissolve any
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
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
B. For lead-coated copper, tin, tin plate, terneplate:
1. Follow instructions for copper, Section 3.01 A.
2. Fasten patches using tinplated cleats or galvanized
iron or steel nails.
C. 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.
D. 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.
E. 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.
F. 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.
END OF SECTION