Rooftop Finale

Upon reaching the roof, the Survivors find a makeshift defensive position in one of the main structures, and must use a radio to alert the helicopter to their presence. The pilot tells them to prepare themselves, and call again once they are ready. Once the second call is made, the helicopter will begin an approach, but the pilot warns that it will take some time to reach the hospital.

The Survivors must then hold out against hordes of Infected which swarm their position, including several Special Infected and at least two Tanks. After fifteen minutes (with the pilot giving periodic updates), the helicopter finally arrives at the partly destroyed helipad, and the Survivors board it to make their escape. The Survivors may trigger an additional wave of Infected by shooting at the rotors of the helicopter as it lands.

It has been reported that if a Tank is allowed to reach the helicopter before it departs, it can wedge its arm inside, and actually prevent it from departing until it is "removed."

With all the Survivors aboard, the helicopter flies off, going behind the hospital before coming around and passing above the camera. The camera fades to black, and the "credits" roll.

The Original Ending
In the Director's Commentary, it is revealed that there was meant to be an ending cutscene after they got on the helicopter. The pilot was meant to complain about how he was attacked while saving another group of people. Afterwards he would have died from the infection, the helicopter crashing into the highway which is the beginning of Death Toll. Valve thought that this left players with an unsatisfactory ending to the campaign. The sound files are still present in the sounds folder.

High Roof Method

 * When you climb up the ladder and first emerge on the roof, do not leave the building that you are on. Instead, select one person to go down.
 * Do not call the radio yet. Instead, the person who jumped down should grab a first aid kit, and bring it back to the building. One at a time, each person stand on the very edge, and let the person heal them. Repeat this until the 3 left up top are healed.
 * The person who dropped down can now call the helicopter. The other three should stay on top, watching out for Smokers and Hunters.
 * Make sure you use the Minigun. Watch out for The Smoker, as they can drag you from the high roof and instantly kill you.
 * The Tank can still get you from where you are. Be especially careful, because there isn't much stopping you from flying off the building and falling thirty stories.
 * It's possible to return to the safe room from here. However, it means abandoning your teammate, essentially leaving them to die while you're safe someplace down below. If you do decide to do this, be aware that the Tanks can still get to you, and they can break down the safe house's door. Find a good spot, and be ready to wait it out. Around the time the second Tank comes, though, you should start making a run for the helipad, as it's exceedingly difficult to run for it through hordes and at least one Tank which spawn when rescue has arrived.

Radio Room Closet Method
There's a closet in the structure with the radio, near the windows and the cache of weapons and ammo. If everyone gets inside of the closet, their backs are covered, and covering the front is exceedingly simple.
 * Once you are on the rooftop, stocked up, and healed, get into the closet.
 * Two people should be near the door crouched and meleeing, while the other two are behind them shooting, preferably with dual pistols to conserve ammo.
 * Once the helicopter is called, all four survivors should stay in the closet, until the first Tank appears. When the Tank appears, all four survivors should leave the closet, and defeat the Tank like normal.
 * When the Tank is dead, return to the closet, and repeat with the melee and shooting formation until the helicopter comes.

-The closet has been removed from the versus version of the game, but it is still in the single player campaign mode-

Helipad Method
The ramp leading up to the helipad has empty space beneath it. The Survivors can easily fit under here, and take on the horde as it files in.
 * Once everyone is well-stocked, go under the ramp.
 * Crouch and back in as far as possible.
 * Have someone activate the radio, and then run back to you.
 * This area functions like the closet, except that you can shoot out through the sides and top (this functions as wall penetration, so damage will be reduced, but the Smoker can't hit you).
 * Once the Tank is spawned it is advised that you leave the ramp until the Tank is dead. The Tank can easily hit all four survivors if they are packed close together under the ramp.

''As of January 14th, 2009, this has been patched on the PC version. The area under the ramp is now filled with crates. The Xbox 360 version has also now been given an update as of February 24th.''

Stairwell Method
In the stairwell in the radio room, there are two doors. Station two people at each door: one person to crouch and melee, the other to shoot.
 * Make sure everyone is well stocked with ammo and such.
 * As long as everyone pays attention, Special Infected can't cause any problems.
 * When Tanks come, scatter, light it on fire, and play cat and mouse until it's dead.
 * When helicopter comes, rush to the pad and get out of there. NOTE: It makes the finale easier if you place some gas tanks, propane tanks, etc. around the pad so you can blow them as you leave, taking some of the zombies out.


 * Due to a Level Re-Design of the Radio House on versus, this stairwell is no longer sheltered by walls and is out in the open.

Glitch Ledge
On the highest area of the radio room, a survivor can get on a small ledge by slowly walking off the roof of the building.
 * In using this area, none of the Infected can reach the Survivors, except the Hunter and the Smoker, but they can be easily dealt with.
 * If playing on one of the higher levels, one of the Tanks may have enough time to actually learn to climb onto your ledge, so make the best of your time!
 * The Untouchables achievement can be achieved through this method.

''This ledge was removed in the versus version, but a similar exploit exists on the high building to the right of the minigun when facing the helipad. Be advised that human Tanks are more likely to toss rocks at you in this position.This has now been removed from the xbox 360 version due to the February 24th update.''

"Jesus Room" Method
Note: This method is considered an exploit. When you first climb onto the roof and face the helipad below, you'll see a building to the right of the helipad(the satellite roof). Go over to it, climb up the ladder and turn right. If you hop up onto this ledge while infected are trying to get you from below and crawl to the very edge, the infected won't be able to get up to you. If you position yourself directly above the door below, the infected will break it open and you can enter the room beyond. The door can also be opened via constant melee, as the door in The Sewers level, but takes considerably longer. This seems to be a room that infected spawn from during the finale, and if you hide at the very back of this room, no infected, special or otherwise, will be able to find you (unless they targeted you while you were entering or you're covered in boomer bile). If you're patient, swarms will eventually die and the tank will spawn. This is where it gets hairy. Sometimes the Tank dies on his own because he can't find you, but this doesn't seem to happen every time, so you may need to go out and kill him. Just remember that if you light him with a molotov and retreat back into this room, he WILL be able to find you. Once the second tank has died, you can run out to the helipad. With some luck, Untouchables can be attained with ease using this method.

"Blind Spot" Method
Note: This method is considered an exploit. There is a point in the map which is invisible to the AI - the only special infected that may get close enough is a Boomer or Smoker, although only the Smoker can attack until the players move. This will not work with bots, since the point appears to be outside their node graph as well.

When stood behind the minigun make a 90 degree left turn. Move forward until you reach the edge of the roof - you will pass between two L-shaped air-conditioning conduits. If you position yourselves between these with your backs to the wall then you're outside the navigation layout for the map. All players must keep backing up against the wall since they will push each other out of place if just left.

You'll hear various hordes and specials spawn in, but none can reach you. If one of the players doesn't keep their back to the wall then you might see a smoker or a couple of common infected, but that's it. All finales consist of of two Tank events - simply wait the first one out until he dies of boredom (frustration). Special Infected that spawn earlier in the battle will also be removed by the director unless they are directly above / behind the survivors.

For the second one you have two options -

1. Run to the Helipad. Once the second Tank is dead the helicopter arrives, so running to the Helipad and killing the Tank en-route means you'll have less zombies to fight. Contrary to normal tactics you should run around the outside of the building here - the Tank will know where you are once you leave the blind spot but as long as nobody does anything stupid you shouldn't get hit.

2. Wait it out. The Tank will eventually die from frustration, at which point the Helicopter will arrive. The problem is that as soon as the Helicopter arrives so does the Horde, Special Infected and so on. Run around the outside again, and throw pipe bombs once you get close to the Helipad.

Note that in both these versions if anyone didn't keep stuck to the wall then a Boomer may be waiting above the blind spot on the ledge behind, ready to vomit as the Survivors leave it - you can hear him burping away so the first player out should do a 180 degree and kill him so that the others don't get slimed.

Untouchables can be attained using this method - managed it on Advanced. Typically you'll have to give it a few goes since somebody usually screws up. Also, it's worth mentioning that since the players are practically inside each other whilst holding place in the blind spot, melee counts as taking damage - even though none is done.

Trivia

 * All throughout the No Mercy campaign there are evacuation posters on various walls, but in the Safe room on the Rooftop Finale there is a poster titled "Infection Warning" and tells you what to do if you think you are infected, interestingly the poster implies pets can be infected.