Inspired by memories of blowing up buildings in my old Space Marine games--along with the fact that I have some nifty Paper Terrain houses that can double as ruins--I came up with this house rule for Blitzkrieg Commander:
Buildings normally count as hard cover, meaning troops inside a building are hit on a 6.
Furthermore, buildings are generally immune to most types of damage. However, they are vulnerable to artillery barrages.
Any time a building comes under fire from artillery (i.e., if a building is covered in whole or in part by a barrage template), it must make a saving throw.
Building saves work the same as for other models with save values, but due to their size and sturdiness buildings roll their saves on 2D6 instead of 1D6.
Saves are as follows:
Wooden structures - 6
Brick or half-timber/half-stone structures - 5
Stone structures - 4
Reinforced concrete structures - 3
If a building fails its save, it is counted as ruined. A ruined building offers only partial cover, meaning troops inside a ruined building are hit on a 5 or 6.
If troops are in a building when that building is ruined, the troops automatically become suppressed. If the troops are already suppressed, they must fall back a number of centimeters equal to the dice total rolled for the failed save.
Building saves should be made after all other hits and suppression results are worked out.
Example: A unit of troops is inside a brick building when the building comes under artillery fire. The troops suffer one hit and become suppressed from the artillery barrage itself. Furthermore, the building fails its save, rolling a "4". As a result, the troops, having become suppressed, must abandon their position in the building and fall back four centimeters.