Don't be afraid to add broken parts ! The house is supposed to still be standing, so don't go too far. You can see that I broke a wooden beam, a pipe, a board, another part of the roof, and a window. When you break something, use the clone stamp tool to fill in the empty space you created.
Make it look dirty. First of all, the windows. I used a non regular brush and painted the windows with a matte color. Then, change the transfer mode of the dirt layer to make sure that dirt and windows blend nicely together. For this example I chose the Luminosity mode.
55