Left 4 Dead video tutorial shows you how to create breakable walls in Hammer Source.
L4D Mapping: Creating Breakable Walls - Video Tutorial
1. Creating breakable wall in Left 4 Dead requires two things.
One: prop_static that is a model of a broken through wall
Two: a brush tied to an entity as func_breakable
2. Position the prop_static breakwall inside a brush to hide it.
3. Turn a brush into a func_breakable by pressing Ctrl+T and assign func_breakable.
In the properites set it the material property and breakable by (infected, tank, everyone)
4. Create infodecal to add variety to the broken wall.
5. Infodecal Properties:
6. Duplicate the infodecal to the other side of the func_breakable entity and change the texture to overlay/brokenwall_mirror
My Output Named: OnBreakder func_breakable properties set the following Outputs:
My Output Named: OnBreak
Target Entity Named: breakwall_decal
Via this Output: Activate
7. Position the infodecals to line up the outside of the walls that line up func_breakable
8. In game test. Point at the wall and type: ent_fire !picker break
9. Rebuild the nav_meshes and spend some time to blend the wall into the environment properly.