When you're always looking down on the structures in your model railroad, roof tops are very important when getting details right. They are some of the first things that viewers will see. Thankfully, there are lots of ways to make them look good because there are so many real-life variations from which to model.
The roof surface itself come in many different forms. Below, I will list some more common types and how to create in n scale.
|Shingles: These are very common on sloped roofs found on residential homes.||Luckily, in the n scale world, this type is usually a texture molded into the surface of a building model kit. No need to DIY anything.|
|Tar paper/rubber membrane: Commercial buildings with flat roof tops are often found with tar paper.||
There are two ways to recreate this roof type:
|Ballast (rocks): Also found on flat roof tops.||Fine to medieum grained sandpaper works very well at recreating ballast. I like using light brown color as you can darken it to make it look more weathered. Look for sheets with some color variations between the grains of sand.|
This link has some great roof detailing ideas: http://www.nscale.net/forums/showthread.php?31487-flat-roofs-on-structures.
It's also important to make sure that you include other commonly found details on your roofs. Flat roof tops lend themselves well to HVAC units, chimneys, duct work, pipes, various metal stacks, and water tanks.
It's all about raising the roof!