One of the things that I really liked about the reference image was that it had several different styles of windows rather than just one. Because of this, the time it took to complete the modeling of each window increased in order to ensure that the slight variations of each window was noticeable (Fig.03).
In the second layer, I found a reference of cracking plaster and duplicated it evenly over the "ledge texture" wood base. With the second layer still selected, I then used a rough-edge brush to get variation with each edge. This was done in conjunction with erasing the areas where I wanted the paint to peel away from the wood. It should be noted that this process was done mostly around 90 degree angles in the modeling (Fig.04b).
After I was satisfied with it, I started to gradually weather the paint with a dirty concrete map that was set to a linear burn with a low opacity for the third layer (Fig.04c). As a result, I started to lose the clarity of the boards below the paint. To fix this, I duplicated the base layer of wood and placed it above all of the grunge layers. I then changed the layer style to Overlay. Keep in mind that you can drop the opacity setting if you want the paint job to appear newer (Fig.04d).
To complete the texturing process, I created another layer. I painted on this layer using an Oil-Medium brush. With this brush I set the opacity to 50% with the understanding that I would most likely be adjusting the opacity layer later. I then painted quickly along the seams between the ledge and where the wall would be. Finally, I set the layer style to Color Burn with a fairly high opacity. My end result can be seen in Fig.04e.
Material Setup and Composite Mapping
In order to really push the visual details and ensure the image will hold up at a high resolution, I like to use Composite maps. By using 2048 x 2048 resolution for your textures, your render quality will look better in small to medium areas, but for larger areas we all know you need to use tiling. Using Composite maps to make your texture look more realistic can be done by breaking the tiling up into multiple layers; this can easily hide any pattern you might create from tiling the base texture (Fig.05).
For the walls, I used two basic layers for my Composite map. In this case, the wood boards acted as the base. For the second layer however, I used the cracking plaster texture again. Initially this didn't look like paint chipping off of wood since I needed to isolate specific parts of that texture. An Alpha map did this for me (Fig.06a - c).
Once this was completed, I simply duplicated the Composite map into the other necessary map slots and I was finished!