Roof

A roof is an area of cover from the elements. They can be natural or artificial, with only minor differences between them.
== Occurrence ==
Constructed roofs are created by pawns; they require no resources to create or destroy and take ? of work to construct. A build roof area designates an area where pawns assigned to Construct will build a roof, and constructors will also automatically enclose newly constructed rooms below a certain size with a roof. If there is inadequate support on a particular tile, a roof won't be built there until there is, but the designated area will remain. A remove roof area does the opposite, designating an area where existing roofs, including thin rock roofs, will be removed and new roofs won't be constructed when a room is enclosed. Removing roofs required and gives no resource's and takes ? of work. Ignore roof area removes the effects of both build roof area and remove roof area - existing roofs won't be removed but new roofs are not designated for construction. If a room is constructed, it will have its roof constructed as normal however.
Natural roofs (e.g. rock roof (thin) and overhead mountain) cannot be created by the player, and only appear in natural rock formations. Thin rock roof can be removed as usual, but overhead mountain cannot be destroyed by any means short of development mode.
A roof can extend up to 6 tiles from a wall, column, rock wall, or any other fully impassible structure. This means that building with interior dimensions 12x(#) or smaller will always be able to be fully roofed. Areas built larger than this will remain partially unroofed without the use of additional support. In addition, a roof must be adjacent to either a roof-bearing structure, or another roof.
If a roof's support is removed after it was built, then it will cause a roof collapse.
== Summary ==
All types of roof do the following, when placed:
* Prevent sunlight from reaching the area, lowering the light level of the tile.
* Block many effects from weather:
** Prevent rain from giving colonists the Soaking Wet moodlet or accelerating item deterioration.
** Prevent snow from accumulating on the ground.
** Prevent lightning from striking an area. Note that any lightning generated in the area, such as by the Flashstorm psycast will still strike if there is an unroofed area, but will simply always strike somewhere unroofed.
** Prevent weather from impacting ranged accuracy, assuming both the shooter and the target are under a roof. The area between the shooter and target is irrelevant.
* Prevent item deterioration completely, if the roofed area is also in a room.
* A room with at least 75% roof allows temperature changes to occur. If a room goes below that threshold, then temperature will instantly equalize with the Outdoors temperature. Having more of a room roofed will increase insulation.
** If the room also has less than 300 unroofed tiles, it will turn from "Unroofed" to "Roofed".
Certain buildings like battery can start a fire when not under a roof and rain or snow begins.
Certain buildings like mortars and ground-penetrating scanners do not function under a roof.
Trees cannot grow under a roof regardless of light level, but other plants can be. Similarly, a roof cannot be built on the same tile as a tree.
Gases dissipate slower under a roof.
== Types ==
=== Overhead mountain (thick) ===
Overhead mountain has special properties compared to regular roof:
*Overhead mountain does not allow transport pods to land or any mortar shells to hit. Pods will land somewhere else; mortar shells are erased.
*Overhead mountain has natural temperature-regulating effects.
*Overhead mountain allows infestations to spawn (see Infestation#Natural Infestations for details).
*Overhead mountain is considered more indoors for an undergrounder's Indoors need.
*Overhead mountain cannot be removed.
*Having a roof collapse will create collapsed rocks, instantly killing or destroying anything underneath. The roof remains the same.
=== Constructed roof ===
Roof put over areas when ordered using a construct roof zone. This roof will make a room considered roofed, however things like mortars or drop pods will break through it if landing on it, causing a small amount of damage from roof collapsing along with any other damage the falling objects would otherwise cause. You can also remove constructed roofs by replacing the construct roof zone with a deconstruct roof zone
=== Rock roof (thin) ===
Near the edge of mountains, Rock Roof (thin) is functionally the same as constructed roof, and unlike thick rock roofs can be removed in the same way as constructed roofs. It cannot be rebuilt if removed or destroyed.
== Roof collapse ==
A roof will collapse if the last supporting structure within 6 tiles is removed, whether by mining, deconstruction, or destruction. Removing the last tile of roof supporting another section of roof by deconstruction will delete the now-unsupported section but will not cause a collapse nor cause any damage. The player receives an event notification when a roof tile collapses and the game is paused.
Roof collapses cause damage to to everything and everyone underneath them, dealing injuries to pawns and damage to items. All roof collapses deal Crush damage. Thick mountain roof deals 99,999 damage with 999% , obliterating anything underneath it. Collapsed overhead mountain will leave collapsed rocks. Pawns and objects caught under collapsed rocks will be utterly destroyed; their bodies, gear, and inventory are unrecoverable. Destroyed items leave no scrap parts. Thick mountain roof is not removed by collapse - if the collapsed rock is mined out and a collapse is triggered again, more collapsed rock will be created indefinitely. 
Normal collapsed roof remove the roof tiles in question and leaves filth in the form of building and rock rubble on the ground. Constructed and thin mountain roof deal between 15 and 30 damage with 0% , targeted at the "outside" and "top" of a pawn i.e. the neck of a human pawn and all its external children parts including the head. 
=== Analysis ===
The player can prevent roof collapse by preemptively removing roof tiles at risk. Creating a Remove roof area on the necessary tiles will prompt a colonist to safely remove thin roof.
Roof collapse can also be manipulated into a weapon to damage entire rooms of enemies at once. Use frag grenades or any ranged weapon to destroy a pillar that was supporting roof over a killbox. Alternatively, IED traps can be placed behind cheap, low walls or columns supporting roofs and enemies shot at when they come near it. They will take cover behind the structure, triggering the IED, detonating it, and dropping the roof on them for two sources of damage. Pathing hacks that exploit pawn preferences to avoid walking over slower terrain can also be used, such as placing IED roof drop traps on bridges over water.
The damage from thin roof drops is not enormous, but targeting the head and neck make it deadlier that it would otherwise be. Assuming the random damage range is linear between the two points, approximately 33.3̅3% of roof collapses will do enough damage to outright destroy the head or neck and instantly kill the pawn. The 0% of the thin roof collapses means that helmets, and to a lesser extent, armor pieces that protect the neck, are very effective at protecting pawns however. This means that heavily armored pawns have little to fear from thin roof collapses except when extremely unlucky, while wearing legendary cataphract armor and cataphract helmet will make you completely immune to them. This also makes Tribal raiders much more susceptible to roof drop traps than the usually better armored outlander and pirate factions.
Nothing will save a pawn from a collapsed overhead mountain and overhead mountain drops are devastating, though difficult to set up and wasteful in terms of loot.
Average thin roof damage by Armor (%)
== Roof deconstruction ==
Drawing a "Remove roof area" will cause colonists to remove a constructed roof. Constructors will automatically go and safely remove the roofs without risk of collapse. Overhead Mountains cannot be removed this way, only by triggering a collapse.
Because of the collapse protection mentioned above when removing the roof, it can be expeditious to direct pawns to only remove the outside ring of roofing to allow the inner roof area to become unsupported and vanish safely. 
== Gallery ==
TempRoof.png|A tile of corrugated sheet metal, used to show new roofs being placed.
Roof placement fading.png|Newly-built roof sections are briefly visible, before fading out.
== Version history ==
* Beta 19/1.0 - It's no longer possible to build roof over trees
* 1.5.4062 - Improved lighting for roof eaves. Gas now dissipates slower in roofed areas.
Category:Buildings
Category:Environment