Care should be exercised on the jobsite to ensure the optimal performance of
prepainted Galvalume® sheet. The first step is to become familiar with the simple
concepts presented on the next pages.
Transit abrasion usually appears as scuff marks or particles of the backer coat which have
been transferred to the top side paint coating of prepainted Galvalume® building panels.
This damage can result from improper paint curing, improper handling or shipping practices
and metal surface irregularities.
The degree of paint coating cure, or hardness, as well as lubricity, may affect the
susceptibility to transit abrasion damage. External rollforming lubricants, internal
paint lubricant additives, and properly formulated backer coats can help minimize
this damage. In some cases a clear, protective, strippable film (Figure 6) is
applied to the topcoat surface to help guard against transit abrasion damage.
In-plant handling of bundled panels can induce abrasion damage. To avoid panel flexing
and consequent panel abrasion, long-panel-length bundles should be lifted with equipment
that supports most of the panel length.
Bundles should be rigidly packaged with crosswise and lengthwise blocking. Truck loadings
should insure that panel bundles are protected from contact with other items such as
structural components. When using a forklift, careful handling and unloading practices
should also be used to avoid excessive bundle flexing or abrasion of the panels (Figure 4).
|Figure 4 - Handling Galvalume® Panels With A Forklift|
When lifting bundles with a forklift, forks must be
a minimum of five feet apart. Do not transport open
bundles. Drive slowly when crossing rough
terrain to prevent panel buckling.
Metal filings, drillings, cuttings and other metal debris, such as pop rivet stems and
fasteners, should never be left on the prepainted steel surface. As the debris weathers over
time it will cause rust stains. These particles should be removed from panels as soon as
they are noticed and swept from the roof at least at the end of each day during construction
Avoid walking on them to prevent damaging the paint film. For critical applications, the
building should be inspected within two weeks after erection, so that any remaining
particles that may have rusted from exposure to dew and rain can be removed. Removing the
last vestiges of metal debris at this time will enhance the long-term appearance of the roof.
Installation Debris Should
Be Swept Away Daily
|Figure 6 |
Some prepainted steel sheets are supplied with a specially-designed clear, strippable organic
film. This film protects the painted surface against abrasion during storage and handling and
should be removed immediately after installation. Sunlight can increase the adhesion between
this film and the painted surface; hence it is vital that the sheets not be left uncovered at
the job site (Figure 6).
When possible, cutting of sheets at the job site should be minimized by using factory-supplied
cut-to-length sheets. If required, panels can be cut by using straight blade shears, profile
shears, nibblers or hand snips.
It is important that all jobsite cutting practices give a clean-cut edge without damaging
the paint or metal coating. The shear blades should be kept sharp to minimize burrs.
Shearing of prepainted steel sheets should be done with the critical (exposed) surface
uppermost so that any small burrs are on the unexposed side.
Never perform field cutting over the top of other painted products. If power cutting
or drilling is required, the area around the holes and cuttings should be masked with
tape or covered with rags to protect the paint from the hot filings. Cutting with an
abrasive disc or hacksaw or burning through with oxyacetylene or similar torches should
be avoided to prevent damage to the paint and metal coating.
Accessory Materials Compatibility
Copper, lead, graphite and unprotected steel should not be used in contact with
prepainted Galvalume® sheet. Water run-off from copper should be avoided. Prepainted
Galvalume® sheet should not be used in direct contact with wet and/or weather-treated
wood or uncured concrete. Wood retains moisture, and weather treatments contain corrosive
chemicals that can shorten the life of a panel in direct contact. Run-off from
chemically-treated wood may also cause corrosion. Uncured concrete is highly alkaline
and may attack the aluminum-zinc coating.
Due to galvanic action, lead and copper flashing can cause accelerated corrosion of
prepainted Galvalume® sheet. Lead flashing is incompatible with Galvalume® sheet.
Copper flashing is incompatible with both galvanized and Galvalume® sheet.
For metal flashing, the preferred alternatives are bare and prepainted Galvalume®
and aluminum sheet. Due to its shorter service life, galvanized sheet should not be
used as a flashing material with prepainted Galvalume® sheet. Graphite-free rubber and
aluminum factory-made roof penetration flashings, such as those for vent pipes,
should be used with prepainted Galvalume® panels.
Handling and Storage
Failure to observe simple but essential precautions when storing and handling panels on
site can lead to damage, delay and expense.
- Panels in bundles should be lifted at their center of gravity.
- When lifting bundles with a crane, a spreader bar and nylon straps
should be used. Never use wire rope slings.
- When using a forklift, forks must be spread a minimum of five feet (Figure 4 above).
- Individual panels should be lifted vertically by the seam.
Do not pick up panels by the ends.
- If the panel is over 10 feet long, lift it with two or more people
on one side to prevent buckling. (Figure 7)
|Figure 7 - Lifting Galvalume® Panels By Hand|
Standing on one side of the panel, lift it by the seam. If the panel
is over 10’ long, lift it with two or more people on one side of the
panel to prevent buckling. Do not pick up by the ends.
The following practices should be used to avoid damaging prepainted Galvalume®
panels during shipment and installation (Figure 8):
- Panels should be kept dry in transit.
- Panels should be handled and installed using clean, dry gloves.
- Panels should not be pulled over rough surfaces, or over each other.
- Panels should be stored off the ground on skids -- at an angle for drainage --
and protected with a loose-fitting waterproof cover.
- If bundles become wet, panels should be separated, wiped with a clean
cloth without delay and stacked so that air circulation completes the drying process.
|Figure 8 - Shipment And Storage Of Galvalume® Panels|
|1. Where possible, do not leave uncovered coils or packs of panels lying in the open. Store indoors and always away from openings to the outside. However, if it is absolutely necessary to store Galvalume® panels outdoors, the
n the following simple precautions are essential.
||2. If packs or coils cannot be kept under cover, erect a simple scaffolding around them and cover with a waterproof tarpaulin or plastic sheet. Leave space between the cover and the sheets to allow air to circulate.
||3. Store packs off the ground and on a slope so that if rain should penetrate the covering, water will drain away.
||4. Inspect the storage site regularly to ensure that moisture has not penetrated the pack.
Backfill and Foundations
Avoid backfilling with soil against prepainted Galvalume® siding surfaces.
If backfilling is inevitable, the sheet surface needs to be isolated from the
backfill by using barrier films.
Ideally, sill plates should be used when installing prepainted sheets over
concrete foundations. However, the prepainted siding should not be in contact
with the sill plate. Sill plates should be tilted slightly away from the
building to avoid trapping water and providing for drainage away from the
edge of the prepainted Galvalume® sheet.
Fiberglass blanket insulation with a vinyl vapor barrier is generally used
on walls and under roofs on buildings with prepainted Galvalume® roofing and
siding. Under circumstances in which insulation contacting prepainted
Galvalume® panels gets wet, inside-out corrosion can occur on the panels.
Vulnerable areas are at wall panel ends at the bottom sill or footing and
at the eave. Insulation should be installed above the sill so that the
insulation won’t get wet and act as a wick to cause inside-out corrosion (Figure 9).
Likewise, insulation not properly tucked in under the roof and at the top of the wall
panels can be exposed to condensation and wind-blown rain, causing underside corrosion
of the roof panel.
|Figure 9 - Typical Siding And Sill Plate Details|
To avoid wet insulation at the footing, several inches of the fiberglass
insulation should be removed from the vinyl vapor barrier at the end of
the blanket. The vapor barrier should then be folded up and around the
insulation, as illustrated, and placed between the panel and the sill
plate or base angle, depending on the footing installation arrangement.
A sill plate arrangement is recommended because it prevents entrapped water,
wet insulation and contact with concrete. In addition, contact between the
Galvalume® panel and the sill plate (or concrete) ideally should be avoided.
Installation practices that allow the insulation to become continually wet
simply should be avoided. Fiberglass blanket insulation under Galvalume® roofs
needs to be installed in such a way that all vapor barrier seams are sealed,
and punctures, penetrations or holes in the vapor barrier are repaired.
Condensation of water vapor on the underside of the roof, along with saturation
of the insulation, can cause inside-out corrosion.
Certain types of field-applied spray-on insulation contain chemical fire retardants
that may be corrosive to Galvalume® sheet. Check with insulation manufacturers
before using such products.
Best Practices ||
Job Site |