Weathering Ngineering's corrugated siding / roofing material       


Weathering this material is very straightforward. In most industrial and rural applications over the last 50 years or so, the corrugated material most often used has been made of galvanized steel. As it ages, it changes from a semi-bright galvanized gray color to a duller gray and eventually shows signs of rust. As the rusting progresses, it further darkens to a darker brown color. Eventually, an entire roof will appear thoroughly rusted.

Siding, on the other hand, is mounted vertically and has faster moisture runoff and less accumulation of matter than can accelerate corrosion. Usually, siding shows sign of rust around material edges first, then random patches where the galvanized coating is thin or has become damaged. Sooner or later though, siding will also become completely rusted and dark, with an appearance just like old roofing.

Keep the aging process in mind when doing a structure that has both corrugated roofing and siding. However the roof is weathered, to appear prototypical the siding should appear in somewhat better condition. Of course, unique climate situations can have unique effects on this type of material. A structure on or near the ocean (a loading dock in a harbor) will have much more corrosion on the windward sides due to the rapid decay caused by salt spray. Alternately, a wayside storage shed that is near a busy track may receive enough grime and oil spray to actually help reduce corrosion. In that case the surface may be blackened with grime.

We have found an excellent aging effect can be achieved by brushing on a lightly diluted application of Model Master #4636 Flat Clear Acrylic. This particular product does a magnificent job of dulling down the corrugated aluminum and giving the appearance of galvanized material. Also, diluted applications of Poly Scale Undercoat Lt. Gray, Milwaukee Road Gray, and SP Lettering Gray to certain areas can fairly simulate the darker dulling of further aging galvanize.  Corrosion can be duplicated with diluted Poly Scale Rust, SF Red, Pacemaker Red and Boxcar Red (for advanced rusting). In all above cases we find that dry brushing or "lightly loaded" brushing gives the best effect. To test for the look you want to obtain, try sample brushing on a scrap piece of aluminum foil. Granted it smooth surface doesn't accurately represent the corrugated material's crest and valleys that trap corrosion (paint), but it works well to get an idea of the colors you like best.

Distressing is another method of weathering this material. Corners and edges can be bent, crumpled, or even slashed with sharp tools to approximate damage. A dented spot on a piece of this material prior to weathering with paints looks just like the dent you would see on the real thing.

Up to now we have focused specifically on galvanized steel material. This material can also be used to represent the siding and roofing material found on many of the newer "steel" buildings that have aluminum siding and roofing. It can be painted any color to fit in with an existing structure where you may need to show its thin cross-section to detail a certain aspect of the structure (an open sliding door, an inside area that has studded walls, a roof section with bracing).

Also, because of this material's .005" thickness, it can be used for roll-up industrial doors or overhead retracting doors. When these use constructed and weathered, they add a terrific appearance to an aged brick loading bay or warehouse entrance.


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