Fallout Shelter rooms

There are a total of 23 available room types that when built begin at level 1 and can be upgraded with caps to a maximum of level 3. Rooms can also be merged up to three times by placing an identical room of the same tier next to it. Generally, each room can facilitate two dwellers. Merged rooms may be occupied by up to 6 dwellers. Production rooms require a specific S.P.E.C.I.A.L trait to run, while training rooms increase a specific trait of the selected dwellers. Production rooms can also rush production.

Floor layout
There are 25 floors; all floors can hold eight rooms. In addition all floors can hold up to two elevators. Adding more than two elevators per floor will sacrifice space for other rooms.

80 is the lowest amount of dwellers needed to maximize end-game activity.
 * Population 80 layout

200 is the population limit.
 * Population 200 layout

Room overview
Rooms in Fallout Shelter typically split into two categories; production and training. The only exceptions are the overseer's office, which enables one to send their dwellers on quests, the vault door which acts as a first line of defense from invasion and elevators which allow dwellers to navigate between floors.

Empty rooms are vulnerable to infestation, If one cannot move dwellers into an empty room to eradicate the problem, the infestation will spread to adjacent rooms.

* n = room size

* p = room level

You start the game with Stimpak and Radaway capacity of 5.

The cost of each new room is dependent on the number of rooms of that type already in your vault. For example, your first medbay costs 400 caps, your second medbay costs 500 caps, and so on.

Production rooms
Production rooms periodically yield one resource, except for the Nuka-Cola bottler, which produces both food and water. Production time is dependent on the assigned dwellers' total trait level for the room's required trait. E.g. four dwellers with Strength 5 in a double-generator room are as productive as 2 dwellers with Strength 10 in the same room. Production times are also modified by the room's size, upgrade level, and the working dwellers' happiness. Although it is not visible in their SPECIAL stat bars, wearing outfits that raises traits beyond 10 increases production rates. Once a room has produced a batch of its resource, it will not produce any more until you collect the resource. Depending on the luck of the workers, collecting the resource may also yield a sum of caps.

Room time
Resource rooms operate with a hidden time pool (hereafter simply referred to as "pool"). Every second all working dwellers in the room add their relevant SPECIAL stat to that pool, increased by the vault's happiness bonus. When the pool is full the room is ready for the player to harvest its resource, after which the pool is emptied and the dwellers need to fill it up again. When a room is merged the pool size is increased to match the new room size. So the pool in a double room is twice the size of a single room, and a triple room thrice the size of a single. Upgrading the room seems to have no noticeable effect on a room's pool size. If a dweller is moved out of the room (perhaps to handle an incident) then the points they've accumulated remain with the room's pool.

So for example in a single-room power plant, a dweller with 5 strength will add 5 points to the pool every second, increased to 5.5 while the vault has the 10% boost from vault happiness. Power rooms seem to have a pool size of 1320 (which is 22 minutes in seconds), however this single dweller will fill up the room's pool in exactly 4 minutes. If the room were to be merged and no new dwellers get added, the room's total pool size is doubled to 2640 (44 minutes) and it would take that same single dweller 8 minutes to fill up the time pool.

The pool sizes for most rooms have been estimated

Efficiency
Bigger is better in this case. Some rooms are more efficient while you actively play (clicking more often); others are more efficient while running in the background. A clear example is the radio room. Although you would think making one 3-room radio is the best way to do it, it is not because if you login after 24 hours, the single room has stopped at 1 citizen, but three 1-room radio rooms give you 3 citizens after 24 hours. This scenario is not 100% accurate since there are chances for you to get 3 citizens, but the fact is that the first scenario stops at 1 citizen and the second one stops at 3 (which is better).
 * (resource*1000/(time*skill))

Why resource*1000/(time*skill)? Because if we increase skill then resources are also increased proportionally. Values are shown for skill 1 workers. 1000 is used because numbers are quite small.

* Quantity is for logging out and resuming after room has finished production (for people who don't care about efficiency while playing, but login, collect resources, and logout).

The above table is for a first tier 1-room. Multiply Quantity and Efficiency with the numbers below to get these values for other configurations:

You can also apply this formula:

$$ Modifier = 2.1^{R-1} * ( 0.9 + 0.1 * \sum_{i=1}^{T} i) $$

where R is the number of rooms merged together and T the Tier of the room

Rush production
Production rooms can "rush" to produce resources quickly. Depending on the probability given in-game, the room can instantly yield resources, experience and a number of caps equal to the percentage of the chance taken. A failed rush attempt leads to an inevitable incident in that room; this may be a fire or an infestation of radroaches/mole rats. Each attempt to rush production, whether successful or not, raises the chances of failure in the next rush. The room's rush penalty slowly decays over time. The total chances to fail a rush in a specific room is affected by the luck and the traits of the workers and the room's current rush penalty. With a successful rush attempt, all workers of a room gain a total of 10 points of happiness over the next 30 seconds. A failed rush attempt lowers the workers happiness by 10 points. Only workers that stay in a room during the entire 30 seconds after the rush will receive the full bonus/penalty.

Pregnant characters will flee a room in the case of a failed rush, and will not help to fix the problem.

It is possible to cap the rush failure chance below 50% with high luck and matching SPECIAL statistics of the workers. At this point, the rush failure chance will alternate between 50% and 40%. If you don't have high luck, the alternating seems to max out at 86% and 74%.

If your goal is to:
 * Produce resources: build big, non-upgraded rooms (for water, food, power) and big, upgraded rooms (for RadAways, Stimpaks)
 * Produce caps: build multiple small, non-upgraded rooms
 * Successfully rush rooms for the quests: build multiple small, non-upgraded rooms
 * Have capacity: do not upgrade (or even staff if you don't want to) the medbay or science labs. You don't get extra capacity from upgrading.

Training rooms
These types of rooms raise one of the traits for the dwellers stationed in it. Dwellers appear to "remember" partial training, so there is no penalty to pulling a dweller out of the gym to temporarily provide some spare power. Training is an important mechanic to improving the effectiveness of your dwellers both in the Vault and in the Wasteland

Training times
Similar to Production rooms, dwellers have a point pool for each of their stats. when this pool fills up the player can level up the appropriate stat. Training time depends on how large the pool is and how fast the dweller can fill the pool.

When training, a dweller adds one point to the pool every second, amplified by the Vault's happiness bonus, the number of dwellers in the room, and the upgrade level of the room.

Pool size of Skill points per level $$ = 1/2(SP^2+SP) $$

Where SP is the Skill Point of dwellers (1 ~ 9)

Points per second $$ = (1+0.02*(D-1)) * (1+0.05*(T-1)) * (1+H) $$

Where D is the number of dwellers training in the room (1 ~ 6)

T is the tier of the training room (1 ~ 3)

H is the Vault happiness bonus (0.01~0.1)

Since the minimum bonus from the vault's happiness is 1.01, dwellers will always train at least slightly faster than the listed base time. Normally this can take roughly 3 days 10 hours. However, dwellers can increase their points per second up to 1.331, which can reduce up to 25% of the time needed to train (training at 4/3 times speed reduces the base time by 3/4) and reducing the total training time to 2 days 12 hours 52 minutes and 36 seconds.

Merged rooms
A maximum of three rooms of the same type can be merged to one bigger room. Rooms are automatically merged by placing a room of the same type next to an existing room of tier 1. If placed next to a room of higher level, the new room will be merged as soon as it is upgraded to the level of the existing room. All beneficial effects of the two rooms are accumulated upon merge: a double training room will train up to four dwellers, a triple training room up to six.

Merged rooms have advantages compared to the same number of unmerged rooms. Upgrading merged rooms costs less than the cumulative upgrade costs of the same number of unmerged rooms, so consider merging rooms to triples before upgrading them. Also, merged rooms are more productive and effective: production rooms will generate resources faster while training rooms can hold more dwellers, which reduces training times.

However, merged rooms have downsides: the bigger the room is and the less it is occupied, the harder/longer it will be to get rid of an incident like radroaches or fire, depleting your dwellers' health faster. Tier also influences the difficulty; the higher the tier, the longer the incident will be. Keep this in mind before trying to rush production in a 3-merged top tier room with only one dweller inside.

A fully occupied merged room can be deadly to invaders if your dwellers are well trained and fully equipped. Make sure the two first floors contain fully merged rooms with trained dwellers to take out most of the intruders.

Mysterious Stranger
Randomly, a Mysterious Stranger will appear in a room for a short time accompanied by an audio cue which is louder depending on his distance from your view. When clicked, the Stranger disappears and you are awarded a random amount of caps ranging from a few dozen to slightly less than 5,000. The Stranger can appear in any room including empty rooms, elevators and the vault entrance, but will not appear during a crisis. If you do not click the Stranger in time, another sound will play and he will disappear without awarding you any caps.

The success animation changes depending on the amount of caps received - for up to 400 caps it is a stream that rushes across the screen to the upper right corner; anything above this threshold manifests as a brief rain of caps across the entire screen.

While the amounts of caps the Stranger awards become less and less significant in later game stages, they are invaluable during the beginning and can greatly speed up a fledgling vault's establishment, especially since the Stranger is much easier to find by this point. As the vault grows, it becomes harder to search quickly and more difficult to find the Mysterious Stranger in time. However, by zooming out to the furthest level and disabling HD Zoom Out in Settings he becomes easier to spot.

Certain pets can increase the frequency of the Stranger's appearance by a considerable margin, to the point that he appears every couple of minutes.