The Perimeter wall was added in Alpha 13 (Version). Any prisoner digging an escape will always go around a perimeter wall if possible as it takes significantly longer to dig through perimeter squares.
Perimeter Wall is one of the four types of walls, the others being
Tip: Perimeter walls are typically a mid to late game upgrade after you have enough prisoners to support a decent income and need the extra protection against tunnel digging. Plan for them early by not laying power lines and water pipes where you will be placing them; but in early stages you can simply put down fencing to save money as your outer wall.
- Perimeter Walls are the strongest walls to dig under.
- Building a perimeter wall will create concrete tiles around the wall.