Patch 5 (version 0.7.0.14356)

Terrans block ramps and seal choke points, and then we sit behind them with guns and tanks. We were the kids who sat up in the tree fort with the water gun shooting at the other kids who couldn’t reach us. And honestly, it was fun.

In Starcraft 2, submersible Supply Depots give the Terrans a new tool to work with when it comes to controlling the wall of buildings. Terran barricades are just as strong as ever for multiplying defensive power and denying scouting opportunities to the opponent. This article will cover a few rules of walling, and some numbers on the Terran repair mechanic.

The Big Idea

Walling off the entrance to your base has a number of benefits for Terran at very little cost. It’s essentially mandatory – you should never not wall-off your base. The main downsides (which we’ll cover) are largely negated by Terran’s ability to remove the wall whenever it wants.

In the early game, your wall helps keep you safer from Zerglings and Zealots. Even a small group of these early game melee troops can cause a lot of damage to Terran if they go unanswered and are allowed straight into the Terran base. You pretty much have to pull workers off your line to deal with this situation, they’ll probably kill some in the process, and your economy will be much weaker than theirs for the effort.

Marines are weak against these units in small numbers, but a well-built wall should not be breakable by a small group of Zerglings or Zealots, even if you only have 1-2 Marines defending it. This lets you spend your resources elsewhere for advantage.

Pay attention to what your choice has just done to the meta game, however. Once your opponent sees your wall, (or more realistically, assumes it because you are playing Terran), they now have less incentive to make Zerglings and Zealots in the early game. They know they can’t cost effectively break your wall. This means you have given them an incentive to tech-up to an option that can get through or around the wall, or they will expand with the hope of just running you over, wall or not.

These are difficult choices for the opponent to make however because the benefit of your wall is two-f0ld. Not only can they not apply early aggression, but they also cannot see what’s happening behind the wall. Protoss has to spend resources and time to get Observers before they can see what you’re up to. Terran has to spend Orbital Command Center energy on Scans, or float buildings over your base to see. Zerg has Overlords early, but those become risky to use later as you have means of shooting them down which costs them time and money.

Since they have no idea what you’re up to, you could very well just be massing troops behind the wall and they wouldn’t know. This means they can’t wholeheartedly forgo early game troops to tech or expand either – they have to be hedge their bets in every direction, which benefits you if you plan on going any one direction quickly. That’s the power of keeping your opponent in the dark.

The best part about the Terran wall is that it doesn’t cost you anything extra over what you already intended to build – you just happen to place a few buildings strategically (that you were going to build anyway) and proceed from there.

If at any time the wall becomes inconvenient to you, you can sink a Supply Depot to move your troops over it and then raise it after-wards, or lift a Barracks or Factory that was used to make the wall. The only real downside is that it gives you extra real estate to cover from harassment – if you’re worried about Dark Templar being dropped in your base for instance, you need detection by your mineral lines AND your wall or ramp. If you’re concerned about Banshees or Mutalisk harassment, you need a few extra Turrets by the buildings at your wall as well.

A wall just requires a small bit of extra investment in these cases, but it’s certainly still worth it.

So how do you do it?

Building Walls by the Map

I’ve included some basic wall placements below with comments in the captions. Make sure you have your Building Grid turned on in the Gameplay section of the Options Menu. It’ll help you see what’s actually walling and what isn’t.

Let’s start with ramps that are common on maps like Lost Temple, Metalopolis and Blistering Sands:

Scrap Station has a very fat ramp at both main bases. It takes some extra building placements to successfully wall it off, but this is balanced by the long ground-distance between the two bases. You have the time you need to build up the wall because ground troops won’t physically reach you in time to stop you. Here’s an example of a wall using two Barracks, and an example of a wall using 1.

The above photo illustrates an important point – the wall isn’t complete until the Tech Lab or Reactor is finished, because units can move through a diagonal space between buildings. Here’s an image illustrating what NOT to do with regards to diagonal walls:

And back to Scrap Station:

Steppes of War’s bottom left spot is a little tricky:

Kulas Ravine is a map where there isn’t a ramp outside your main that can be blocked in this manner. Instead, there is a very narrow choke point which can be blocked by using a single Barracks and Supply Depot. Here are a few examples starting in the top left of the map and going clockwise around all of the starting points:

I recently watched a replay where CowGoMoo (one of the best Terrans in beta currently) started in this spot. The Protoss applies early pressure and takes down the depot, proceeding to raze his base. CowGoMoo decides to win anyway, but it certainly wasn’t made easier by losing the wall. You can see it by clicking on this link here to SC2RC.com.

Note that the Supply Depot is always either above or below the Barracks in these photos – that’s an easy way to remember how to do it on this map. If you have the option, you always want to have the Barracks be ‘furthest out’, and your Supply Depot be in the safer, closer spot. The main reason is that Supply Depots have less health, but they are also repaired slower than a Barracks as well.

Terran Buildings and Units all have individual repair rates in SC2, and it has no correlation to their maximum hit points. Each building or unit just has a set rate that they are repaired at. This is important to know because it helps us plan around keeping our wall up when an early rush does happen.

Do-It-Yourself Wall Repair

Inevitably, someone will test your wall because they built the troops to do it and they think you’re skimping out on Marines behind that wall in order to tech or expand faster. Well-enough; let’s do this.

Let’s say someone comes at your wall with a few Zealots, and you have 1 or 2 marines behind it to keep it up. They only have to break one Supply Depot to get through – how many SCVs do you need repairing it to keep it up? I’ll spare you the math and the details and just let you know that you need about 1.5x – 2x SCVs for each Zealot they bring to the fight to outpace their damage. Realistically, I’d bring 1.5x because your Marines are going to kill off a few before they successfully kill the depot.

In the case of Zerglings? Well for 6 Zerglings, you need 4 or 5 SCVs to keep that depot up. Again, I think you’d be fine with 4 SCVs because your 1 or 2 marines will kill them off and lower their damage output pretty quickly.

Beyond just testing it out, there’s a way we can figure these things out in our heads. Each SCV repairs about 10 health per second on a Supply Depot on Faster mode. Zerglings do about 10 damage per second (DPS) each on Faster mode, and Zealots do about 20 damage per second each on Faster mode. If you’re curious where these damage numbers come from, check out the SC2 Unit Damage Chart by clicking here (it’s a Google docs spreadsheet). The numbers it shows are for the game played on “Fast” mode – if you want the unit’s DPS on “Faster”, multiply the listed DPS by 1.33.

It does take a significant amount of SCVs to keep a wall up against concentrated damage, but keeping that wall up and killing off those troops is certainly better than having them break through and kill off your defenders and economy anyway. Realistically, your opponent will test your wall, see they can’t break through and give up. If they persist, now you know how many SCVs you’ll need to keep it up.

What About Those Repair Rates?

It’s weird, isn’t it? Here’s what my testing has found so far – it’s not entirely scientific, but I gave each building a few test repairs from Orange to Full and used a stop watch to come up with these numbers. I’d say these are very close approximations:

Supply Depots are repaired at ~10 Health Per Second (HPS).

Barracks are repaired at ~18 HPS.

Tech Labs and Reactors are repaired at ~10 HPS (in case they try and break that instead of a Supply Depot).

Command Centers are repaired at ~14 HPS.

Planetary Fortresses are repaired at ~9.2 HPS.

Bunkers are repaired at ~11 HPS.

Missile Turrets are repaired at 7 HPS.

Units vary in repair rates as well:

Tanks are repaired at ~4 HPS.

Thors are repaired at ~7.5 HPS.

Battlecruisers are repaired at ~7 HPS.

SCVs (woo!) are repaired at ~5 HPS.

The big thing to take away from this is that a host of repairing SCVs are probably not going to save your siege tanks from incoming damage, though they can patch up wounded ones with some time. Since Thors can be easily swarmed by SCVs, that definitely makes keeping them alive with repair much easier.

A Few Last Thoughts and Best Practices

There is no reason to not use walls to your advantage, and now you should know the exact ways to place them on the current set of maps. Be very careful to not completely forgo building troops because you have a wall however – walls are much easier to get around in this game, and walls are no substitute for having an actual map presence with troops. Think of the wall as multiplying the defensive power of the troops you already have rather than making up for troops you don’t.

Watch out for things like Protoss Pylon/Warp Gate tricks to get uphill into your base. Just remain vigilant and scout around the edges of your base with a Marine. Terran Reaper rushes can also sidestep your wall, as they can jump over cliffs to get into your base easily. A few extra Marines early on can handle these, no problem. Reapers are relatively weak in straight-up fights and represent a significant gas investment from the other Terran.

Don’t let your wall keep YOU from scouting, either. Scouting is the easiest way to avoid being out expanded or surprised, and you should definitely drop the depot and get some Terrans out there to figure out what is going on.

Also, Jeff had a great tip/comment on the “New Tools for the New Mutalisk” post – SCVs have a large auto-repair range now, so you can comfortably place Turrets near your mineral lines and keep a hotkey of SCVs set to auto-repair. If Mutalisk, Banshee or Void-Ray harassment begins, just flip to that hotkey and hit “S” to stop them from mining. They’ll automatically begin repairing the Turrets, or whatever is under attack, which buys you time to get your troops over there and stop it.

This could easily be an early game habit for you as you sit there making SCVs and waiting to build your first Supply Depot, hardly costing you anything later on.

If you’re having trouble walling-in on a certain map or in a certain spot, share it and we’ll figure out an answer!