LEFT 4 DEAD: Can you create breakable walls that L4D zombies can break if it's positioned face down?

I was wondering if Left 4 Dead zombies have the capability of breaking through walls if it’s positioned face down?
A lot of the walls on my map have slopes or uneven surfaces so I’m trying to create alternative entrances that zombies can break through.

If you were mapping for l4d2 you could have marked the wall BREAKABLEWALL when doing the nav mesh but i think for l4d you might have to make a trigger and turn the walls to func_breakable

If the zombies don’t break it you could also place a trigger above it and make it break the wall on contact.

Wouldn’t just be easier to make the breakable wall part a func_brush, set it to solid and to flag it to Break on Touch?

No such flag exists for func_brush. You don’t get any gibbing or destruction sounds with it anyway.

The best method, as said before, is to make a func_breakable with a trigger on top of it. I’ve used it before and it worked like a charm.

It was just an idea in case the zombies can’t break trough vertically but taz0’s method is basicly the same and will work perfect for the first L4D.