Here's the newest building that I have added to the Nouvion terrain board. Just like the rest of the buildings, it is made out of pink underlayment foam. This is a quick review of how I go about making these: https://wappellious.blogspot.com/2016/06/houses-in-hurry.html
The pink foam has many advantages. It is ultimately a lot cheaper than foam core, and easier to work with. You can cut it very easily, and texture it as well. Cutting it into thin 'detail' pieces such as those around the windows is very handy for adding more levels of that detail to your buildings.
It does not take much to make the "ruined" look on the buildings, and it is very easy to measure out the various sections. Once I work out the measurements of a structure, I make a template of the different pieces so that I can make more of that same building.
The biggest advantage of the pink foam is that I can paint them without having to worry about the walls warping. Foam core has the paper backing, which absorbs the moisture and makes things warp. The pink foam takes the Stynrlez primer quite nicely! Here's an example: https://wappellious.blogspot.com/2018/08/terrain-time.html
Here's the painted version, which is now featured in the town of Nouvion! Battle reports on this new table are imminent :-) https://wappellious.blogspot.com/2018/12/building-nouvion-part-2.html