General Guidelines For The Repair Of Sheet Metal Aluminum Features
- Procedure code:
- Developed For Hspg (Nps - Sero)
- Metal Materials
- Last Modified:
GENERAL GUIDELINES FOR THE REPAIR OF SHEET METAL ALUMINUM FEATURES
A. This procedure provides general guidelines for making
simple repairs to aluminum features made from sheet
metal. These include roofing, flashing, gutters,
downspouts and leader heads, and miscellaneous other
rainwater goods. For repairs to other types of aluminum
features see procedure 05010-09-R, "General Guidelines
for the Repair of Three-dimensional Aluminum Features."
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).
C. For general information on the characteristics, uses and
problems associated with aluminum, see 05010-08-S.
A. Technical Report #C-6: "Aluminum and its Alloys," The
Aluminum Association, September 1978, fourth printing,
B. Technical Report #35: "Specifications for Aluminum Sheet
Metal Work in Building Construction," The Aluminum
Association, August 1980.
C. "Metal's in America's Historic Buildings: Uses and
Preservation Treatments", U.S. Department of Interior -
National Park Service - Preservation Assistance Division,
Chapters 8 and 18, Revised 1993.
D. Aluminum Association
900 19th Street NW, Ste. 310
Washington, DC 20006
A. Protect aluminum architectural elements with non-
absorptive, insulating coating to prevent direct contact
with corrosive agents.
B. Protect aluminum architectural elements from rainwater
run-off from wood and copper roofs and copper gutters.
C. Where concealed aluminum touches masonry, coat with a
heavy-bodied bituminous paint followed by two coats of
aluminum metal and masonry paint.
D. When aluminum is painted for cosmetic reasons and there
is no incompatibility with other building materials,
prime with a zinc chromate primer and apply two finish
coats of compatible paint from the same manufacturer. DO
NOT USE lead-based paints or paints with copper
containing anti-fouling agents.
A. Aluminum to match existing in finish, alloy (unless
failure was caused by the use of an unsuitable alloy for
the conditions), temper, thickness, color and appearance.
B. Aluminum cleats of same finish, alloy, temper, thickness,
color and appearance as sheet goods being repaired.
C. Aluminum nails, screws, bolts, nuts washers, expansion
inserts, rivets, wedges and plugs as required by repair.
Must be of an appropriate thickness, alloy, temper, etc.,
for intended use.
D. Building paper or roofing felt: Minimum weight shall be
15 lbs. Papers containing additives of heavy metals or
chemicals corrosive to aluminum shall not be used.
1. For roofing over non- or poorly vented spaces, use
a vapor barrier or polyethylene sheet not less than
4 mils thick.
2. For roofing over well vented spaces, use a water-
repellent material (not necessarily water proof).
E. Sealants (for use with mechanical methods of joining
sheet goods where watertightness cannot be achieved with
a standard seam):
1. 1-part synthetic or rubber-base sealants. Use
shall be in conformance with manufacturer's
2. 2-part synthetic or rubber-base sealant. Use shall
be in conformance with manufacturer's
F. Elastic cement
G. Paint for back painting/priming shall be bituminous paint
of cut-back type. Where appearance is a factor, use
methacrylate type lacquers.
H. Filler as appropriate for base metal and joining
technique being used. Consult manufacturer.
I. Flux as appropriate for metal and joining technique being
A. Gas tungsten-arc or gas metal-arc equipment as
appropriate for welding repair.
B. Torch, iron or hot plate as appropriate for brazing
C. Fire extinguisher
A. Verify the aluminum type prior to the installation of
replacement material. Failure of feature may be the
result of using the wrong type of alloy for the
environmental conditions encountered.
A. Surface Preparation:
1. Prior to making repairs, remove all oil, dirt, and
other debris from the surface.
2. All surfaces which are to be covered with aluminum
shall be smooth, even and free of small bumps and
hollows. All surfaces shall be dry both before and
during the placing of the aluminum.
a. Wood: Lumber shall be well seasoned, straight
and free of knotholes and splits. All joints
shall be true and even and firmly attached
with all fastener heads flush with the top
surface. All surfaces shall be covered with
building paper or painted with two coats of
any quality exterior type paint or the
aluminum shall be back primed.
b. Dissimilar metals: To prevent galvanic
corrosion from occurring, aluminum in contact
with dissimilar metals shall be protected by a
non-absorptive, insulative coating.
c. Concrete and masonry: These surfaces shall be
covered with building paper or the back side
of the aluminum shall be painted. Where
aluminum is to be inserted into slots or
reglets, the slots or reglets shall be filled
with sealant so that the sealant covers both
surfaces of the aluminum in the slot or
3.03 ERECTION, INSTALLATION, APPLICATION
A. For Mechanical Joining:
NOTE: REPAIRS TO FLASHING, GUTTERS AND DOWNSPOUTS,
ROOFING, ETC. CAN BE MADE USING STANDARD SHEET METAL
1. For repairs to aluminum sheet metal roofs and
flashing, follow recommendations of the aluminum
association. See also the following procedures:
a. 07602-01-R, "Repairing Pinch Cracks in Long
b. 07610-02-R, "Installing a Transverse Expansion
Joint in a Standing Seam Copper Sheetmetal
c. 07610-03-R, "Repairing a Bowing Sheetmetal
d. 07610-04-R, "Repairing a Wind-damaged Copper
Sheetmetal Roof Ridge and Installing a New
e. 07620-02-R, "Repairing Chimney Flashing".
B. For Brazing:
1. For temperatures above 8400F, brazing must be done
under shop conditions only by an experienced
2. Use brazing only on those items where joint design
allows for the complete removal of flux residue.
C. For Field Welding:
NOTE: WELDING SHOULD BE EXECUTED ONLY BY A SKILLED
WELDER UNDER CAREFUL SUPERVISION.
NOTE: USE CAUTION IN HANDLING FLAME TOOLS WHEN WELDING.
THE DANGER OF SETTING THE STRUCTURE ON FIRE IS ALWAYS
PRESENT. COMPLY WITH FIRE, SAFETY AND ENVIRONMENTAL
CAUTION: DURING WELDING THE METAL BECOMES VERY HOT AND
CAN UNDERGO TREMENDOUS THERMAL SHOCK.
1. For large sections, welding should take place off
site. The piece must be removed and transported
to a workshop where it can be preheated before
welding and postheated after welding to ensure a
gradual temperature change within the metal.
2. Use gas tungsten-arc or gas metal-arc welding
3. If the aluminum has anodized coating, the coating
must first be removed from the surfaces to be
welded to permit proper fusion of the surfaces.
4. Use materials and methods that minimize distortion
and develop strength and corrosion resistance of
5. Obtain fusion without undercut or overlap.
6. Remove welding flux immediately.
7. At exposed connections, finish exposed welds and
surfaces smooth and blended so that no roughness
shows after finishing and contour of welded surface
matches those adjacent.
8 Advantages of welding:
a. Arc welding produces a strong, durable
connection and, if properly executed, is at
least as strong as the surrounding metal.
b. It is faster and less expensive than threaded
connections, which require drilling a pilot
and then tapping to accommodate screws or
c. Welding is the most preferred for the
attachment of the decorative castings and for
other non-structural repairs for economic
reasons and because it allows to preserve the
original damaged elements, which otherwise
would have to be replaced.
9. Disadvantages of welding:
a. In cases where the original attachments are
bolted, the use of this method may result in
internal stresses (welds cannot move with
seasonal expansion/ contraction cycles) which
may in turn lead to further breaks.
b. Welding may leave a 'bead' along the surface
of the connection which may be unacceptable in
some restoration projects, even though much of
the weld may later be ground down, depending
on the location and the welding material.
D. For Oxyfuel-gas Welding:
NOTE: WELDING SHOULD BE EXECUTED ONLY BY A SKILLED
WELDER UNDER CAREFUL SUPERVISION.
1. Use ONLY under shop conditions to insure complete
removal of corrosive fluxes.
2. Metallic bond (gas) welding is more reliable than
fusion (arc) welding in repairing large sections
because a lower temperature is used and heat is
applied and removed at a slower rate.
F. DO NOT SOLDER ALUMINUM SHEETMETAL.
END OF SECTION