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Pre-painted Galvalume® Sheet:
A Guide to Best Practices

The product is a 55% Al-Zn alloy coated sheet steel manufactured and sold under the trademark GALVALUME by Bethlehem Steel Corp, Dofasco Inc., National Steel Corp., U.S. Steel Group of USX Corp., and Wheeling-Nisshin, Inc. It is also manufactured and sold by Steelscape, Inc. under the registered trademark ZINCALUME®, by Industrias Monterrey S.A. under its trademark ZINTRO-ALUM™, and by Galvak, S.A. de C.V. under its trademark GALVAL™. Prepainted GALVALUME roofing and siding panels are used on buildings everywhere. Architects and building owners have turned to prepainted GALVALUME steel panels because their clean lines, unlimited spectrum of colors and long-term durability enhance the appearance, life and value of buildings.

Prepainted GALVALUME sheet combines well with most other building materials and treatments. Its versatility allows it to be used almost anywhere on building exteriors, assuring compatibility and simplicity in the overall design approach. GALVALUME is sheet steel with a hot dip-applied alloy coating of about 55% aluminum and 45% zinc. Its excellent corrosion resistance has been proven by field performance on buildings for more than two decades. An estimated 40 billion square feet of prepainted GALVALUME sheet covers buildings in all kinds of climates and environments in North America, Europe, Asia and Australia. The combination of long-lived GALVALUME sheet with a wide range of modern high-performance paint systems results in a functional, durable, eye-appealing building product.

Ensuring that prepainted GALVALUME sheet will give the best possible performance is the joint responsibility of building panel manufacturers, architects and contractors. But even the best products can perform better if they are used with that extra attention to detail characteristic of quality and craftsmanship.

This brochure describes the best design, manufacturing, installation and maintenance practices for prepainted GALVALUME Sheet.

Manufacture
Steep Pitch

Steel Roofing The manufacture of prepainted GALVALUME sheet panels starts with the GALVALUME steel substrate and its exceptionally corrosion-resistant aluminum-zinc alloy coating. Next, this high-performance coated steel passes through modern high-speed continuous coil coating lines that carefully apply and oven-cure the paint systems. The painted product is made to rigid specifications and quality-tested to meet critical laboratory performance requirements established by ASTM and paint manufacturers in cooperation with the National Coil Coaters Association (NCCA). After painting, the coils are ready for forming into versatile, eye-catching roofing and siding panels.

Finishes

Prepainted GALVALUME sheet is supplied with a factory-applied, baked-on finish. Processing on the paint line includes cleaning, pretreating, priming and top coating with a uniform paint finish, all in one continuous process.

A schematic diagram of the prepainted GALVALUME sheet system is shown in Figure 1 (below). GALVALUME sheet, with its highly corrosion-resistant aluminum-zinc coating, serves as the foundation for the paint system. A chemical pretreatment is applied to promote adhesion between the paint and metal coating surface. A high-performance primer is applied to the pretreated surface to enhance corrosion resistance, particularly at cut edges, scratches and bends. The system is completed by applying a colorful, durable paint selected for the performance requirements of the application. Typical topcoats include acrylics, polyesters, siliconized polyesters, fluoropolymers and plastisols.

Figure 1 — Prepainted GALVALUME Sheet System
Layers

Durable, beautiful finishes acrylics, polyesters, siliconized polyesters, fluoropolymers, plastisols in almost any color you want (Layer 1).

High-performance primers are key to long-term corrosion resistance and paint adhesion (Layer 2).

Pretreatments provide excellent corrosion resistance and adhesion (Layer 3).

An aluminum-zinc alloy coating about 55% aluminum, 45% zinc. Quite a force in fighting corrosion (Layer 4).

Uniform steel sheet properties are a result of modern steelmaking technology (Layer 5).

Backer coats to enhance corrosion resistance and minimize abrasion damage (Layer 6).


It is recommended that the unexposed or back side be pretreated, primed and coated with a "backer" coat. The backer coat is applied to enhance performance and appearance, and to minimize abrasion during shipping and handling. The back side may be coated with a full paint system similar to the exposed side. Refer to paint manufacturers for specific recommendations.

Table 1, prepared by NCCA, provides a guideline for selection of generic paint systems for particular applications. Coating systems should be specified with the assistance of technical service representatives from the GALVALUME sheet producers, coil coaters and paint manufacturers.

Typical Paint Coatings

Profiles

Rollforming
Sheet Fed Coils

Rollforming is most commonly used to form prepainted GALVALUME sheet into roofing and siding panels. Rollformers consist of a series of shaped rolls mounted on stands that progressively form the sheet fed from a coil into panel profiles (Figure 2).

Prepainted GALVALUME sheet can be readily formed into an almost limitless variety of shapes and profiles, depending on the strength and ductility of the GALVALUME sheet, the characteristics of the paint system, and the type of rollforming equipment and its maintenance (Figure 3).

Figure 3 — Some Rollformed GALVALUME Profiles
Ripples

To enhance the field performance of prepainted GALVALUME sheet, especially at formed areas, the good practice guidelines in Table 2 (below) should be followed.

Table 2 — Good Practice Guidelines for Rollforming Prepainted GALVALUME Sheet
  • Use panel designs with large bend radii. It is possible to design architecturally desirable, deep profiles, and at the same time, use large bend radii.
  • Design the rollformer so that profiling occurs from the center of the sheet out towards the edges.
  • Design the rollformer to accommodate the strength of the steel grade. For example, a higher strength steel may require more rollformer stands to successfully produce a given profile.
  • Use lower strength steels to allow greater design latitude when making more complex profiles.
  • Maintain the rollforming equipment to achieve proper vertical and horizontal tooling alignment, as well as adequate clearance between the mating top and bottom spindle rolls to avoid abrading the coating. Clean the rolls to avoid damage to the paint finish.
  • Incorporate the appropriate number of rollforming stages to ensure smooth transitioning of bends.
  • Use flexible paint/primer systems to maximize performance at bends.

Other Types of Forming

Rollforming is by far the most common type of forming for prepainted GALVALUME sheet. However, for applications where prepainted GALVALUME sheet is used for wall and/or roof panels, there will very likely be a need to press-brake form trim parts and other accessories. Again, it is important to use the maximum permissible bend radii to enhance the performance at bends.

Equally important for press-brake forming is the need to protect the painted surface from scratches and abrasion. This can be accomplished by using polyurethane or a similar hard plastic material for the dies. Proper tooling clearances should be maintained during this operation.

Roofs

Roll embossing is another type of forming that can be applied to prepainted GALVALUME sheet. Care must be exercised to assure that the paint and metallic GALVALUME coating are not damaged during embossing. The depth and sharpness of the embossment should be sufficiently gentle to assure that the durability of prepainted GALVALUME sheet is not compromised.

Other types of forming, including stamping, notching and piercing can be applied to prepainted GALVALUME sheet. Many of the factors discussed previously, such as die clearance and good paint system flexibility, are equally important considerations for these types of forming. For example, stamping is used to form prepainted GALVALUME facsimile roof tile panels, mainly used for residential roofing.

Job Site
Red Roof

Steel Roofing 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

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
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.


Installation Debris

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 (Figure 5). 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.

Figure 5 —
Installation Debris Should Be Swept Away Daily
Sweep away debris
Figure 6 —
Protective Strippable Film
Peel protective film

Strippable Film

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).

Field Cutting

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.

Flashing

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
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
Shipment & Storage
  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.

Insulation

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
Typical Siding and Still 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.

Fasteners
Steel Roofing

Because GALVALUME sheet roofing and siding are long-lasting products, it is important that fasteners have a service life equivalent to that of GALVALUME panels and accessories. Fastener costs are minimal relative to the overall cost of a building project, so no benefit is gained by using inferior fasteners. The correct selection of a fastener is important for long-term structural performance and aesthetics.

A wide range of fasteners is available for use with prepainted GALVALUME sheet. These fasteners are also supplied in self-drilling and self-tapping types with various metal and graphite-free polymer washer combinations to suit the fastening requirements of panel manufacturers.

Driving Fasteners

Fastener materials include carbon steel, 400- and 300- series stainless steel and aluminum. Carbon steel fasteners are available with special heads that include cast zinc-aluminum, nylon and 300- series stainless capped heads. Fastener manufacturers can also top coat metal fasteners with factory-applied polymer coatings that color-match prepainted GALVALUME roof and wall panels. (Note: Carbon steel fasteners are available with electroplated and mechanically-plated zinc and cadmium coatings; however, these coatings typically are too thin (0.5 mil. or less) and not recommended for prepainted GALVALUME sheet.) For all fastening applications, users should be guided by recommendations of fastener and panel manufacturers.

Steel Roofing During installation fasteners should be properly tightened and not overdriven or driven at an angle (Figure 10). Leaks can potentially occur at improperly-seated fasteners, as well as at underdriven fasteners or fasteners that "back out" over time. Water leaking at fasteners can saturate insulation and cause inside-out corrosion. Overdriving a fastener may also cause a depression on some panel profiles, which can then collect water and accelerate corrosion. Driving tools equipped with depth-sensing nose pieces and suitable RPM speeds can assist in avoiding these problems. Impact-type tools should not be used.

Sealants

Double-bead and triple-bead tape sealants are commonly used at overlapping panel ends on roofs and at laps on roof ancillaries such as curbs. Sealants are also available in tubes for flashing and ancillary sealing. Sealants should be sandwiched completely within the lap and not applied on the panel surface, where they can be degraded by UV radiation. Roof panel manufacturers can provide design details about placement of sealants at overlapping panels, ancillaries and flashings.

Butyl, polyurethane, acrylic and silicone sealants can be used. Neutral cure silicones are recommended. Acid cure silicones liberate corrosive by-products that smell of vinegar. Only aliphatic urethanes should be used. Butyl sealants should be used where there is no exterior exposure, such as between laps. Only acrylics containing very high solids (>80%) are recommended. Sealant manufacturers can make specific recommendations about flexibility, resiliency, UV tolerance and weathering.

Steel Roofing


Edges

Cut Edges

Cut or sheared edges expose the steel, metallic coating and paint coating to the environment, thereby creating a galvanically-active area at which corrosion can begin. The degree to which such corrosion occurs at a cut edge depends on the thickness of the sheet, the paint system, the environment and the angle of exposure, i.e. vertical (wall panels) or sloped (roof panels).

Roof Drip Edges

Roof drip edges on prepainted metallic coated sheets are subjected to the most severe cut edge corrosion because rain and dew collect and are retained at such edges. The initial sign of corrosion at roof drip edges is usually visible as microblistering on the surface of the panel back from the cut edge. As time goes on, paint microblistering continues to creep back from the edge.

On some metallic coated products, paint microblistering continues at a steady rate and eventually red rusting occurs on the surface of the sheet near the edge. Prepainted GALVALUME sheet shows microblistering, but its rate decreases with time. Thus, over the long term, prepainted GALVALUME sheet provides better performance than conventional metallic coated sheets at roof drip edges.

Sidewall Drip Edges

For prepainted GALVALUME sidewall drip edges, no significant corrosion is noticeable to the naked eye when proper installation practices have been followed. These practices are described in Table 3.

Table 3
 Good Practices Guidelines To Avoid or Minimize Paint Microblistering At Cut And Drip Edges
  • When roof panels are sheared or cut in the shop or field, the burr produced by the shear cut should be placed down to limit water retention at the edge.
  • Drip or drain ends on roof panels at eaves should be bent down slightly to avoid collecting water on both the top and bottom sides of the panel.
  • If possible, particularly in severe marine and industrial environments, field-cut edges should be painted or otherwise protected, such as with shielding trim parts.
  • Sidewall panels at the ground level should not contact the concrete footing. Water can collect at the crevice contact point between the panel and the footing, as well as infiltrate into insulation on the inside wall, which can cause inside-out corrosion. To isolate the sidewall panel from the footing, sill plates that provide adequate drainage should be installed on the concrete footing (Figure 9).

Vertical Edges on Siding

Slitting of the vertical or long edges of prepainted GALVALUME siding is not recommended for applications where the slit edge is boldly exposed to the environment. Building panel manufacturers should order prepainted GALVALUME sheet for roll forming that will give the required finished siding width without slitting to size and thus avoiding exposed cut edges. The long edges of such full width GALVALUME sheet are protected by the GALVALUME coating and paint "wrap around" during hot dip metal coating and paint coil coating.

Overlapping Roof and Sidewall Edges

Corrosion is less severe at overlapping edges along the sides and ends of prepainted metallic coated panels than at drip edges, because rain and dew drain freely and are not retained at overlapping edges. Where possible, full-length panels should be used on roofs and walls to avoid short, overlapping panels with sheared ends and exposed cut edges.

Trim and Sidewall Fitted Edges

Cut edges are also present on trim and sidewall fitted edges around doors and windows. The cutting practices described under "Field Cutting" should be used for clean, burr-free edges when fitting sidewalls around wall openings. Such cuts should be protected and hidden from view by trim parts. Where possible, trim parts should also be bent and hemmed so that the cut edge is folded out of view.

Design
A Guide to Best Practices

Steel Roofing A wide variety of seams, joints, ribs, fastening devices and surface treatments is possible, enabling designers to develop almost any desired effect. Prepainted GALVALUME sheet in building systems and components can be designed to match or coordinate with textures and patterns produced by many other building and cladding materials, including exposed concrete, wood and glass curtain-wall systems.

Building systems and components fabricated of prepainted GALVALUME sheet are strong and lightweight, permitting their use for special effects not possible with other materials. Their light weight means less structural deadloading and greater freedom in the use of slender architectural elements.

Flexibility in color choice also provides greater opportunity for the selective use of metal on facades, in combination with masonry, concrete, wood and other materials. For projects that combine other exterior finishes and materials with metal, the availability of prepainted GALVALUME sheet facilitates matching or complementing desired colors.

Roofs and Mansards

The superior appearance and performance of today’s prepainted steel sheets has resulted in a resurgence of interest among architects and owners to make the roof visible. Roofs have become a design feature and are no longer just an element to keep out water. Metal roofing systems produced from prepainted GALVALUME sheet offer potential for using roof colors that complement the color of the other architectural elements. A wide variety of roof panel widths and seam effects can be achieved.

The slope of prepainted architectural GALVALUME roofs is generally steep, typically 3:12 or greater, to provide fast runoff of water. Roofs with lower slopes often are not visible, so unpainted GALVALUME sheet is the material of choice. For lower roof slopes down to 1/4:12, unpainted GALVALUME roofs are more economical and have demonstrated excellent performance after more than 20 years.

Architectural roof panels are usually applied to a solid deck rather than directly to the roof purlins. Decking can be wood or steel. Thirty-pound felt paper or equivalent is typically used between the panel and deck. Some architectural prepainted GALVALUME roof systems are designed for direct attachment to the roof substructure. Panel profiles are generally flat and about 10 - 24 in. wide. Minor longitudinal ribs may be formed in the panel for strength and form.

Panels can be fastened to the deck using through-panel, exposed fasteners or by concealed clips or fasteners. Panels are lapped or joined at longitudinal seams. Seams are generally variations of standing snap-together seams or batten seams. Batten seams can be traditional box batten or cap batten, as well as integral batten seams. Snap-together and batten seams typically range from about ¾ in. to about 2 in. high. Panels with snap-together seams or traditional batten seams are attached to the deck with concealed clips or cleats that are fastened to or fixed into the seam. Integral batten panels are fastened with clips or directly to the deck with concealed fasteners. Clips and cleats are typically designed to be movable so that thermal expansion and contraction of the panels can be accommodated.

Siding

Building panel manufacturers offer a wide range of prepainted GALVALUME sheet profiles for siding. Large facade areas can be covered so that panel appearances and desired architectural effects will be uniform over the entire area of application. High-quality prepainted GALVALUME sheet panels assure that color rendition and panel appearance will be uniform throughout the project.

Similarly, trimwork, stops, copings and other elements critical to the overall design effect can be executed using the same materials, treatments and colors that are used for coverage of larger exterior areas. The technical problems of transitions and joining are minimized by using identical materials.

Maintenance
A Guide to Best Practices

Steel Roofing With a little care and attention during service, prepainted GALVALUME sheet will provide an extended service life. While durable, factory-applied finishes for metal building panels will last many years longer than ordinary paints, they should be cleaned thoroughly on a routine basis whenever the finish is not washed by rain. Applications where the paint finish is automatically washed by rain, such as roofing, do not require this maintenance.

Cleaning restores the appearance of the building, making repainting unnecessary, and maintains a pleasing appearance, as well as removing the buildup of corrosive materials. Applications requiring maintenance cleaning include soffits, siding under eaves, garage doors and the undersides of eave gutters.

Cleaning

In many cases, washing the painted surface with clean water from a garden hose will remove most of the dirt and accumulated deposits. Ideally, washing should be done at least every six months and more frequently in coastal areas where marine salt spray is prevalent or where high levels of industrial fallout occur. In cases where spray washing is ineffective in cleaning stubborn dirt, mild detergents or household ammonia solutions can be used as described below. In all cases, test a small unobtrusive area for color-fastness before cleaning large areas.

  • Use one cup of Tide® (or other common detergent containing less than 0.5% phosphate) dissolved in five gallons of warm water. NOTE: Detergents containing greater than 0.5% phosphate are not recommended for use in general cleaning of building panels.
  • OR use one cup of household ammonia dissolved in five gallons of water at room temperature. Never mix ammonia with any kind of bleach.
  • Never blend cleaners and bleach yourself. If bleach and detergent are required, use detergents containing bleach.

Using either solution, work from the top to the bottom of panels with a well-soaked soft cloth, sponge, brush with very soft bristles, or low-pressure spray washer to clean the surface. Washing from the top down avoids streaking. Application should be gentle to prevent shiny spots. Scouring powders or industrial solvents are not recommended, since they may damage the paint film. Solvent-containing cleaners such as Fantastic® are very effective and can be used.

If mildew or other fungal growth is a problem and cannot be removed as described above, detergent containing bleach, such as Tide® with Bleach, is recommended. The surface should be thoroughly rinsed with water after cleaning to remove traces of detergent.

Touch-Up Paint

If scratches occur during handling and installation of painted roofing and siding, it may be desirable to use touch-up paint to repair the blemishes. Misuse or over-use can result in spoiling the overall appearance. Surface scratches which are not too obvious from a distance of six feet are generally best left untouched, since normal soiling and weathering will mask them.

Touch-up paint should be used sparingly and only to cover up those areas where paint has been removed. Areas to be touched-up should be wiped with mineral spirits to remove dirt, wax or other contaminants before colored touch-up is applied. Touch-up painting of large areas is not recommended, because these paints will not weather as well as factory-applied finishes. Contact the building panel manufacturer or original paint supplier for the appropriate touch-up system.

Aerosol or spray applications are not recommended for blemish or scratch repairs. The best tool for this type of repair is a good-quality ½ in. or smaller artist brush.

If cared for according to these instructions, prepainted GALVALUME sheet will maintain its original appearance longer.