Up on the roof
The roofs of our model railroad structures are a very prominent feature as we normally view our layouts from above. Numerous details can be added that make the roof look more prototypical. These details include roof top HVAC systems, ladders, vents, pipes, and numerous other details. In addition, depending on the type of structure, the roofing material can range from asphalt shingles, metal, tile, tar and gravel, and several different types of roll or roofing membranes. Time spent detailing the roof will pay off with a structure that looks great and adds realism to your model.
One easy way to simulate a tar and gravel roof or roll roofing is by using spray paint. The two paints I used are Rust-Oleum Automotive Primer #2081 Light Gray, and Rust-Oleum 2X Ultra Cover #280711 Flat Black. If you are replicating a roll roofing material as seen in the above photo on my Georgia Metal Coaters structure, the first step is to cut blue painters tape into 3’ wide scale strips. Starting on the side where the roof would be sloped to drain, apply your first piece of tape and press it firmly to the roof base. The next row slightly overlaps the first row. Vertical seams that occur when one roll ends and the next roll begins can be incorporated with overlapping the previous piece by 6 to 12 scale inches. After you have the tape applied you can move on to the next step.
Painting the roofing using this technique is the same if you applied the tape to simulate roll roofing or selected to model a tar and gravel roof. The first step is to apply the Light Gray Automotive Primer in a few light coats to the roof. Let it dry for a few minutes, then apply the Flat Black paint by lightly “dusting” it on the roof from 12” to 18” above the surface. The paint should rain down on the roof and leave a speckled look, as seen in the photo. Don’t worry if it looks too dark or heavy in one area, the next step will tone it down. For the final step, apply the Light Gray Primer again, dusting it from above as you did with the flat black. If you mess up an area you can always repeat the process until you get the correct coverage of each color. It takes a little practice to get it right, but once you do you’ll be pleased with the effect. After the paint dries, if you chose to model rolled roofing, you can simulate the black tar that is applied to the seams by using a black Sharpie marker.
The spray painting technique also does a good job of replicating the look of tar and gravel roof. Here the roof was painted using the techniques described and a few details were added. Note the "tar" around the plumbing vent stack applied with a black Sharpie marker.
Another type of roofing is a thermoplastic roof membrane, typically used on restaurants and industrial structures. This type of roof is highly reflective, resistant to UV light and most chemicals, making it ideal for businesses that emit oils and/or fats from their ventilation systems. I decided to replicate this type of roofing on my DQ Grill and Chill restaurant. Most of these types of roofs are a light color so I painted the roof white. I used a fine point black sharpie marker to draw in the seam lines at 3 foot intervals. I also drew in mid-row vertical seams on a few random rows. I installed an HVAC unit that is a casting I purchased a few years ago along with the air ducts. I also installed a kitchen style roof ventilator from a Walthers kit and plumbing vent stack made with styrene tubing on the roof. The final step was to apply some Pan Pastel weathering powders to give the roof a weathered appearance. The addition of these few details and the painted roof really enhanced the look of the restaurant. I hope you give some of these techniques a try and see how it improves the look of your structures.