prevent biter expansion

[NO]

what method is used to prevent biter expansion into to cleared areas? radar?

[Bimmelkaes]

walls, turrets and artillery

[PaulieZero]

Radar paired with artillery will detect them and then blast them. This usually triggers an attack against the artillery station.

You could consider more advanced solutions like artillery trains that patrol a perimeter.

In the long game you can make spidertons, have at least one following another one, and then remotely send them on a patrol around the map using the remote control device.

[LCD]

i shut it off lol.

[NO]

dont have arty yet not even close.

i will put defense and radars thru ought hope for the best

[Xandor]

Normally you can put turrets spread out, so they cover the area but you don't need to make a wall of turrets since only a few biters appear when they make expansions.
Good to do it at chokepoints so you don't need to cover that much ground.

On the map I am playing now I used 6 turrets to block ~25% of the map, 6 turrets to block off another ~15% of the map. 4 turrets to cover another ~10%. The other ~50% is still open so they could expand from that side.

[Khaylain]

Having walls keeps biters unable to get into your factory without destroying the wall, and having turrets along the walls will keep them from being able to nom on your wall that easily.

[Budmind]

i usually go with a double wall (2walls right next to each other) with 3 flamethrower turrets behind the wall (place the the turrets so that their attack cone starts at the outer side of the wall)
with how the new fluid system works its very easy to just drag a pipe to the wall and have some alien barbecue

[Chris!!]

I have walls but no turrets (only placing them if they touched the walls before) since I try to claim big areas with natural choke points and cannot be bothered to cover every nook and cranny with turrets. Also make sure no nests are inside your walled off territory, you might get a nasty surprise otherwise.

[Naustghoul]

FIre... lots and lots of roasty toasty fire. And bullets. And arty. And more lasers. ALWAYS more lasers. Because... lasers.