Historic Preservation - Technical Procedures
- Repairing Holes In A Sheetmetal Roof
- Procedure code:
- Hspg Prepared For Nps - Sero
- Thermal And Moisture Protection
- Sheet Metal Roofing
- Last Modified:
- Repairing Holes In A Sheetmetal Roof
- Last Modified:
REPAIRING HOLES IN A SHEETMETAL ROOF
A. This procedure includes guidance on patching holes in a
sheet metal roof by brazing and welting. GENERALLY, THIS
WORK SHOULD BE ACCOMPLISHED BY A EXPERIENCED ROOFING
NOTE: DO NOT USE ASPHALT ROOFING COMPOUND OR CHEAP
ALUMINUM-BASED ROOF COATINGS TO MAKE THE PATCHES. THESE
REPAIRS SELDOM LAST, AND ARE HARD TO UNDO, AND ARE
POTENTIALLY DAMAGING TO THE EXISTING ROOF.
B. Falling masonry, scaffold poles, and other objects are
responsible for inflicting damage to many roofs at some
time during their life. Damage is mostly of a minor and
localized nature, and in the case of a fully supported,
traditional metal roof is usually no more than a shallow
indentation in the metal and supporting boards, with
perhaps a small rupture in the covering at the base of
C. 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 or snow covered roofs. Work on
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
rope of sufficient strength
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. They may be distorted which can
affect the slope to drain.
D. 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. anneal--the operation of heating and cooling the metal to
soften it and make it less brittle.
B. brazing--to solder with a non-ferrous metal that melts at
a lower temperature than that of the metals being joined.
C. cleats or clips--metal 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 roofing in position, made from
same material as roofing.
D. solder--metal or metallic alloy of tin and lead used when
melted to join metallic surfaces.
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 QUALITY ASSURANCE
A. Qualifications: Metal roof systems and their accessories
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
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
B. Keep the roof clear of debris, and trim all overhanging
branches that might cause mechanical damage.
C. In addition to scheduled inspections, inspect after each
exposure to unusually severe weather conditions such as
strong winds, hail, or long continuous rains.
D. Never use any black goop (asphaltic roofing compound) or
caulk to seal joints on a metal roof. Asphalt attacks
metal roofing, and no caulk lasts long enough for this
A. Revere Copper
C. Metal Sales Mfg. Corp.
D. Vulcan Supply Corporation
E. Fine Metal Roof Tech
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. Nails of metal appropriate for metal used:
1. For terne or terne-coated stainless steel: Use
2. For copper: Use copper nails or brass screws
B. Cleats, same material as roof
C. Sheetmetal to match remainder of roof
E. Soldering flux
F. Rosin Paper
G. 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
H. 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
A. Whenever possible, make inspection from ground, or from
above if possible.
B. Inspect roof parts for signs of warped, cracked, split,
or out of place sheets, pulled fastenings, broken joints
and seams, excessive weathering, or metal punctures.
C. Inspect the underside of the roof deck from the attic to
detect leaks. Flashings are the most vulnerable points.
Therefore, inspect the underside carefully at all
flashing points for evidence of leakage such as water
A. Surface Preparation:
1. Carefully examine, measure, and record existing
sheetmetal patterns at edges, hips, ridges, and
other special conditions.
2. For safety of the personnel, keep the deck clear of
waste material as the work proceeds.
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.
3.03 EXECUTION, INSTALLATION, APPLICATION
A. For Small Repairs:
1. Thoroughly clean the area to be patched of all rust
and/or roofing cement. When finished, the metal
should be bare and shiny.
2. Cut a metal patch, using the same material as the
roof, to the required size and shape. Fold the
edges under 1/2 inch and snip off the corners (this
makes the patch stronger and takes off easily
damaged sharp corners).
3. Place a weight, such as a brick, over the patch to
hold it firmly to the metal. If the patch is on a
steep slope or vertical surface, clamp or tack-
solder it in place.
4. Soft solder the patch over the defect. For
guidance on soldering, see 05010-07-R "Procedures
for Soldering Metal".
B. For Medium-Sized Repairs:
NOTE: SILVER BRAZING REQUIRES EXTREMELY HIGH
TEMPERATURES, SO THE METHOD CAN ONLY BE USED WHERE
THE METAL CAN BE RAISED FROM THE DECKING ALLOWING A
FIRE-RESISTANT INSULATION SHEET OR PAD TO BE PLACED
BETWEEN THE TWO. THIS WILL REQUIRE A NEARBY SEAM
TO BE UNFOLDED.
a. Carefully remove the damaged piece of metal
b. Level the indentation in the decking with a
suitable wood filler.
c. Silver braze the new metal to the existing bay
using a "dog tooth" joint to hold the edges
together and prevent undue distortion.
2. Welting: If fire precautions make it impractical
to use brazing, try welting:
a. Welt a new square of sheet metal into the
existing damaged bay. Make sure the metal
patch is the same material as the existing
b. Replace rosin paper underlayment as required.
c. Seal the welt by flowing soft solder under the
final fold and into the mitered corners using
a large copper bit.
d. Pre-tin the edges of the new and existing
metal and dress the welt tight to create a
capillary soldered joint for maximum strength.
C. For Large Repairs:
1. Remove the damaged sheets carefully.
2. Repair the decking.
3. Replace the rosin paper underlayment.
4. Close the covering with new metal, matching
original seam type, pan size, metal type, etc.
Install new clips or cleats as required.
A. At the end of each work day, provide building protection
for any exterior roofing element removed for repair or
B. Work only on a quantity of roofing which may be repaired
on that same day. At the end of the day, use 15 pound
roofing felt or polyethylene sheeting to drape over
missing roofing and insert under roof unit laps or
temporarily secure areas of existing roofing and roof as
required to make roof watertight and windproof.
END OF SECTION