Gemini Rules for Warhammer 40,000.
Building Rules

        The following rules for Buildings may also be used to play games set inside spaceships or other large vehicles.

Movement and Combat in Buildings.
        Movement and combat in buildings can be handled in two ways. If you have sufficient room to set up the interior of a building on the tabletop you can use normal tabletop rules. Different floors of the building can be set up on different parts of the table.

        When fighting inside a building on the tabletop most of the usual tabletop rules are used. A door can be moved through by any model that has sufficient movement allowance to reach it and pass through it. Ramps and stairs are treated as normal ground but will take the model to a new level.

        Furnished or Cluttered Areas count as either Difficult Ground or Variable terrain. Areas with collapsed ceillings, very dense rubble, wreakage or machinery may be Variable or Very Difficult Ground.

        For ladders either use the actual measured distance or assume that each level requires 3” of move allowance to move up or down. Climbing ladders does not require an Initiative test. If a ladder between two floors requires 3” of movement to climb completely a model with a 4” move 3” from a ladder is considered to use 3” of the move reaching the ladder and 1” climbing. If it is not killed or otherwise stopped while climbing on its next turn it can climb the remaining 2” of ladder and move a further 2” on the next floor.
        No more than four normal human-sized models may mount or leave a single-width ladder on any turn. Ogryn and Terminators can be considered to be equivalent to two models each.
        If while climbing a model takes damage it will fall even if the damage was saved. See MOVEMENT page for rules on falling. A unit that assaults via a ladder does not get any Charge bonuses.

        The unit coherency rule that all members of a unit must be within 3” of another can be waived for combat in buildings. Members of the same unit will usually be in the same room or enclosed space, or in an adjoining one.

Doors
        Bolting, locking, unlocking, opening or closing a door -any combination of TWO of these actions reduces move by 2”. Three or four such actions reduces the move that turn by 4”.

        Doors and windows 1” or lower than do not count as obstacles. To move through a door or window a model must have sufficient move allowance to take it through the doorway. If a model's movement places it blocking a doorway other models passing through the door in the same turn that traveled further are moved past it, it being assumed they entered before. A model that is halted because they used their move unlocking and opening the door can be assumed to stand aside to let the others enter.
        If more than one model ends its move in the doorway one model is placed in the doorway and the others placed in a rank in front of it and touching bases. In the next SHOOTING phase only one of these models can fire. Select which one randomly if they differ. All of these models can be targeted by an enemy, however. This represents them clustering at the bottleneck.

        In Rogue Trader rules the number of models that can pass through a doorway, window or opening in each turn was limited. No more than four models could pass through a single opening even if they all have sufficient move. The number of models that could pass through each opening per turn depended on their move speed.

Number of Models that can move through a Standard-sized door.
        This assumes a normal-sized single door and human sized figures.

Basic Move Allowance.
Models passing through door per turn
3 ½”+
4 models
2½- 3½
3 models
1½- 2½”
2 models
less than 1½”
1 model

        Ogryn and Terminators can be considered to be equivalent to two models each. At more than 3-4 metres tall a Dreadnought could not pass through a normal door and would probably make its own. How large an opening a Dreadnought will require and if the machine can enter the building interior at all is up to the GM. See later for rules on breaking through walls and doors.

        The above rule can be considered to be optional for Gemini Rules. It is simpler to let as many models that have sufficient move to pass through an open door. Large Size Two models will find it more difficult to pass through single doorways designed for normal Size Two creatures. If a Size two model is mounted on a base wider than the opening they wish to pass through then movement through it costs an extra 1” of movement.

Blocking Doors
        A normal-sized model can chose to block a single door. A double door would need two blockers or a bigger blocker. Only one attacker at a time can engage the blocker in Close Combat. The blocker always has Initiative and has +1 to hit in Close Combat. Blockers cannot be routed. They can only be moved if attacked from the other side of the door, effected by psychology, killed or they choose to move away. A larger creature may block a single door but since it would not actually be in the doorway it can be attacked by more than one attacker, so Ogryn-sized creatures that are blocking a normal door can be attacked by two attackers.
        Other features such as narrow bridges, ladders or grapple hooks can also be blocked.

Breaking Down Doors and Walls
        Doors, Windows and Walls can be attacked with ranged or close combat attacks. Wounds inflicted on non-living targets are referred to as Damage Points.

        Objects such as doors, normal-sized windows and walls are hit automatically if shot at from a distance of less than 2”. If at a greater distance a door or window is a man-sized target (so no modifiers) and a wall section a large target (+1).
        Most doors have a Toughness of 6 and take between 1 (light wood) and 10 (bank vault) damage points to break them down.

        Damage for Doors
Light Wooden door
1
Toughened Glass/Plastic door
2
Light Steel door
3
Solid Timber door
4
Heavy Steel/Airlock door
5
Vault door
10


Building Composition and Damaging

CompositionToughness.
Solid Timber wall
8
Brick/Stone/Concrete
8
Plexi-glass
8
used in Plexi-shelters
Travel-Tube wall.
8
Light wood
6
including improvised barricades
Sheet steel
7
Corrugated iron
7
Most Flooring
7
Wood, sheet steel or synthetic
Light Flooring
6
Reeds or matting over wooden frame.
Wattle and Daub
6
Thatch
6

        Each hit that causes one point of damage creates a hole big enough for the passage of one human-sized creature per turn. Such an opening can be treated as an opening 1” wide. Large Size Two creatures require an opening made by at least two points of damage.
        To destroy a 6” section of wall a certain number of damage points must be inflicted.
        A Mud/Straw/light wooden or tin shack requires 3. A Plexi-shelter section takes 5. Most building wall sections take 7 while a stone castle wall would take 15.
        A linked double weapon might be allowed to inflict two points of damage on a hit. Creatures or weapons that do S+2D6 damage against vehicles do D6 points of damage when attacking walls or doors. In other words troops with Chainfists can go through bulkheads a lot quicker than those with Powerfists.

        Remember that when firing against buildings any damage creates an opening that can be treated as a door or window.

        If a wall section looses all its damage points it may be ruled to have collapsed, depending on the material it is made from. Any models within 1½” of the collapsing section take a hit equal in strength to the wall section's Toughness. Armour saves are permitted. The collapsed wall area is treated as very difficult ground, 6x3”.

        If you prefer to use Vehicle Attack Rules for Buildings the basic conversions of Toughness to Armour Value are:-

Toughness12345678910
Armour Value78910111213141516

        Optional:- If desired each 6” section of wall can be treated as six 1” parts. Each 1” part has one sixth of the damage points of a 6” section, rounding up. If a 1” section looses all its damage points it is treated as a 1” open door but debris makes it difficult terrain and 2” of move is needed to pass through it. If two or more adjacent 1” wall sections are destroyed there is a danger of collapse. Roll a D6 and if the number rolled is less than the number of breached sections the entire 6” wall section collapses (see above).

  
Firing Into Buildings.
        When firing at buildings one option is to simply fire at the building. This is resolved as normal with most buildings being considered to be large targets and therefore +1 to hit with Non-Area and Template weapons. Area weapons that deviate scatter their shots outside the building as will be described later.
         When firing a Non-Area weapon at the occupant of a building open doors or windows provide no obstruction to targeting -on the contrary they provide Line of Sight. Shooters can also fire in through the windows and doors and such openings are considered to be normal sized targets so have no modifier to hit. An enemy firing from an opening is however at –2 to hit for using hard cover. Targets further inside the building if visible are also usually –2 since it is assumed they are using interior walls and furniture for cover. When shooting in through an opening when using Building Section rules it is assumed all targets are in hard cover. If the occupants of the building are unaware they are about to be fired on this cover modifier can be waived at the GM's discretion.

        Shooting through a window, door or opening you are facing is fairly easy. If you are at an angle you effectively have a smaller target. If at an angle of 45° or less to the wall the opening is on all shots at or through the opening are subject to a -1 modifier. This applies to direct fire weapons, Grenades, Template weapons and to the Deviation role for Area Weapons.

        Grenades or rocks that are thrown to pass through windows or doorways more than 2” from the thrower must pass a roll against BS. If the door, window or opening is 1” size or smaller then this test is at -1. If the BS roll is not made the grenade will explode outside the building/in the same room as the thrower.

        Area weapons and grenades can be fired or thrown against the outside of a building. They can also be targeted against a point inside the building so long as the user has Line of Sight through a open window, door or any other normal-sized or large opening. Such shots follow the Area Weapon and Obstruction rules given in the SHOOTING pages.
        If the a Hit is rolled on the Hit/Scatter dice the marker is placed on this point. If the shot deviated it may not have passed through the opening. The deviation is worked out to determine the position the marker should be placed in. Position the marker as dictated by the deviation roll as though the cover was not present. Take a line from the centre of the marker back towards the shooter. If there are no obstructions or other features that would have intercepted the shot leave the marker where it is. If the shot would have hit an intermediate feature or model move the marker back along the line until it is at the feature nearest the shooter. The centre hole will be on the side of the cover nearest the shooter but the marker may still cover enemies behind the cover. These may be hit but have a chance of not being effected as described above in Area Weapons and Cover.

        The blast of an Area Weapon may be subject to the Confined Spaces rule. In a roofless or high- roofed building the targets may avoid being hit due to interior hard cover between them and the blast.

        A Grenade or Area weapon fired or thrown through a normal-sized window or door from a range of 2” or less is taken to automatically succeed in passing through the opening. If the shot from an Area Weapon deviates the scattered marker is positioned inside the building. Modify blast effects for confined spaces or hard cover as appropriate.

        Barrage fire or Indirect fire cannot be targeted on the interior of a building unless there is an opening in the roof. Such fire that does hit the building will affect the roof and uppermost floors of the building first.

Template Weapons
        If using a Template weapon the user has the options of either attacking the building or firing through any open windows or doors. If the template cannot be positioned over an open window, door or similar-sized opening the shot can only be made against the building. The template is placed as normal but the shooter can declare that he is firing at a storey one level above or below the one he is at.
        A shot against a building is treated as normal but models inside the building under the template cannot be hit unless they are within 1” of a open firing port or opening. Models near such openings are in Hard Cover. If the required roll against BS is exceeded by two or more they are hit automatically. If a partial hit is scored they are hit on a 4+. Many buildings will be large targets so are automatically hit if one less than the basic target score against BS is rolled. If less than this is rolled they are hit on a 4+.
        If the template can be positioned over one or more standard size or larger open doors, windows etc then targets inside the building can be attacked. Use the normal Gemini template rules for “outdoor” firing but be aware that some models under the template may benefit from still benefit from hard cover. If there is an unobstructed line between weapon and target it is not in cover while those with walls etc between them will be in hard cover so you need to exceed your target BS roll by 2 to hit them automatically. If the target score is not beaten by at least 2 each figure behind cover is only hit on a 4+. If any part of the template is in contact with the exterior of the wall the building itself may also be hit by the shot. Firing template weapons against very small openings such as firing ports will be covered in the next section.

Confined Spaces
        Using Grenades and Area or Template weapons inside typical buildings is subject to the Confined Spaces rules. A typical building in this context can be taken to mean one with a normal height (3” or less) intact ceiling. The Confined space rule also applies to corridors, tunnels and most caves. A Cathedral, Hanger or roofless ruins would not be treated as a Confined Space so would use the standard Area marker or Template rules.

        If fighting on a tabletop use the usual scatter rules for Area weapons to find where the shot/grenade lands. If it lands inside a confined space you don't need the usual Area markers; everyone within that room, friend or foe is automatically hit, the blast being considered to stop at the walls. Models within 1” of a doorway, window or other opening to a room an Area Weapon explodes in will be hit on a 4+. This rule assumes that the room is the size of a single building section or smaller. If the area of the detonation area is larger than 25 square inches or has a side of more than 6” treat the weapon as having an effect area of 3” radius from the point where the munition landed. If the shot landed within 1” of a solid wall then the effect radius is 4” in other directions. Cover from interior features such as furniture provides no protection in a confined space blast. The GM may rule that if the interior walls are of a thin material (such as plastiboard or thatch) then the effect area does not stop at the walls and has an effect area of up to 25square inches or 3” radius. If a thin wall was between the model and the blast centre reduce the chance of being hit to a 3+.
        Use the same rules for weapons that use a 5” diameter template, but also roll for damage against the walls the blast touches.
        Attacks with Template weapons in Confined spaces may splash back from walls so at the GM's discretion the shape of the effect area may be different. Both furniture and interior walls provide hard or soft cover and a chance of not being hit although protection from furniture may be negated by splash from nearby walls. Flamer shots can be bounced off nearby walls or ceilings for round the corner shots.


Building Section Rules.
        The other way to handle buildings is by charting the interior as a collection of sections. This is a more abstract method where models inside a structure or vehicle don't need to be represented by actual models on the tabletop. Building Section Rules are usually used when indoor combat is only a minor component of the battle and avoids the need to design a building interior and position every occupant. Vehicle interiors are often treated in the same way as building sections.

        Each floor of a building is considered to be made up of one or more sections. Most building stories will be one section. As a general rule a section can be taken to not exceed an area of 25 square inches so each floor with a greater area is divided into two or more sections. For example, a floorspace of 36 square inches would probably be treated as two 18 square inch sections. Sometimes the shape of the building will make it obvious that more than one section should be used. Two towers connected by a low building would obviously have three ground floor sections. A single building section will also not be either longer or wider than 6” so a corridor 2” wide and 12” long will be treated as two sections.

Movement through Building Sections.
        Movement under Building Section rules resembles movement on a chess board. Units move one section at a time rather than a specified number of inches.

        Each section can normally hold no more than twelve normal-sized models. This may be temporarily exceeded during a Close Combat round. Models can move from one section to an adjacent one providing their route is not obstructed in someway. They can move to a section separated from theirs by a wall if there is an open door or other opening. They can move to a higher or lower section if there is a staircase, ladder or ramp. Movement is one section per MOVEMENT phase regardless of what the models' movement allowance is. Faster creatures are considered to be slowed down by the cramped conditions.

        Building sections are assumed to be filled by furniture and interior walls which restricts movement and line of sight. If building sections represent a large open space such as a courtyard the GM may allow models with a move of 6 or more to move two sections per turn. This includes Assaulting Units that have a charge of 6 or more, allowing them to charge from two building sections away rather than into just the adjacent section. Shooting range may also be increased.

Shooting and Building Sections.
        Up to six models in a section may fire out of it, range being taken as being from the building edge. If enemies are visible in more than one direction this rule may be modified if the GM wishes so that up to four models may fire to any one quadrant. If a building was being attacked from all sides it is likely most of the occupants could find a firing position.
        Models firing out of a building section can be targeted at -2 (for hard cover) by shooters outside. Models inside a building section that are not shooting or looking out cannot be targeted by models outside unless the models outside are within 2” of a open door or window. If Building Section rules are being used then models inside the building section being fired at in through windows are -2 to hit to allow for the cover given by walls and furniture.
        Units in one building section firing upon those in another adjacent building section shoot at -2 to-hit. Normally shooting between building sections can only be between adjoining sections, it being assumed interior walls and furniture prevent more distant targets being hit or even seen.

        An Area or Template shot or grenade that lands in a building section automatically hits every occupant of that section if the section is ruled as being a Confined space. If the GM rules that the section has interior walls and furniture that would provide Hard Cover some or all of the occupants may have the chance of being hit reduced to a 3+ . If the Building Section is an open interior space such as a courtyard the GM may allow a 4+ chance of escaping a hit.

        To fire an Area weapon into building section from outside the shooter must be in range and have a clear line of sight though a window, door or opening. If using “Building Section” rules (rather than tabletop rules) the GM has the option of any miss or deviation being taken to have exploded harmlessly on the outside of the building. Work out scatter only if a unit outside the building could have been hit. It is assumed that a shot that enters an opening explodes in the building section immediately beyond

        When using a building section rules a grenade or Area attack from one section to another section still needs a to-hit roll to be made. If the shot fails the to-hit roll roll another D6. On a roll of 4 or less the weapon still hits the building section aimed for. On 5+ the grenade lands in the neighboring building section which may be thrower/shooter's. If there is a choice of more than one randomize with a dice roll.

        If the exterior of a building is hit by an Area or Ordinance weapon and using building section rules the GM must decide how many occupants are eligible targets using the position of the marker and how much of the structure it covers as a guide. It can be assumed that all firing positions towards an enemy are manned and the remaining occupants distributed evenly through the rest of the section.

Close Combat and Building Sections
        A unit can Assault a unit in another section providing there is access between the sections. A unit that has to move from one section to another via a ladder does not get any charge bonuses.
        If the architecture permits models may jump down from a higher level into Close Combat. They get a charge bonus for this but must take one Initiative test for every full 2” jumped down or take damage as described in the Climbing section. If they fail their Initiative rolls they take D3 S4 hits each if they were one section higher, D3 S8 if two sections higher and so on. The same penalties are used if models fall from a height.

        Enemies fighting in the same section are assumed to Melee. A unit can attack a unit in a connecting section. D6 members of the attacking unit fight D6 members of the attacked unit per turn (roll separately). The defending unit is treated as being in cover for the first round. A unit that routs is assumed to have been totally destroyed in large games. If the players prefer the routing unit is ejected from the building. Attackers that fail to destroy or rout the defenders do not enter the contested section, as described below. The winning side does not have to pursue unless they wish to.

        A unit in a building section can be charged by a unit outside and on the tabletop. The unit inside count as being in cover. Rather than use the door rules above assume that two attacking models may move through each doorway or window and that models are be fought “one to one”, one defender fighting each attacker. Alternately have D6 attackers fight D6 defenders. The former system is better for larger buildings while the latter is better for surprise attacks or smaller structures.
        If the Attacking side destroys the defenders or causes them to rout the Attacking unit occupies the building section. If the defenders rout all models in the section are assumed killed, or if preferred they are ejected and rout. The defenders will flee from the side of the building or section opposite to the Attackers. The winning Attackers may choose to occupy the building section rather than pursue and do not have to test not to pursue unless subject to conditions such as Frenzy.
        If the Defenders win the combat round, draw or lose the round but do not rout the Attackers fail to take the building. They are moved back 1” and are no longer considered to be engaged. The Defenders are not obliged to pursue and may not if they drew or lost the round. The Attackers do not have to Consolidate next turn and may attempt to storm the building again next turn if they wish.

        A unit in building section may charge out to attack an enemy outside the building. This combat then follows normal tabletop rules.


Bunkers.
      A military bunker is treated like an immobile enclosed vehicle with Armour of 13 or better. The general rule that only half the building's capacity of models within can fire does not apply to bunkers since they will be well provided with firing ports. One model can fire from each firing port or every inch of length of a firing slot.
        Troops inside will lock the bunker during a battle so if the bunker is intact only friendly models may enter it. This may not be the case for infiltration scenarios. Troops inside an intact bunker cannot be engaged in Close-combat although the bunker itself can be subjected to Close-combat attacks.

        Most bunkers will constitute a single Building Section. If the bunker is larger than this treat hits and damage to each section separately.

        Glancing and Penetrating hits are rolled against the Bunker hits table below modified from page 133 of 3rd Ed.

Glancing HitPenetrating Hit 
1 No Effect: A little dust falls from the ceiling but no real damage.
2*-3 Occupants Shaken: May not fire in their next turn but may move.
41-2*Occupants Stunned: May neither fire or move in their next turn.
53-4Structural Damage: Subsequent rolls on this table have a +1 modifier. This is cumulative so another Structural Damage result will give a +2 modifier and so on.
65-6Collapse: Bunker destroyed. Each occupant takes a wound on a 4+ roll but an armour save can be attempted against this. Survivors are placed up to 2” from the destroyed bunker.

        *If a bunker has any functioning built in weapons treat a roll of 2 on the table as a “Armament Destroyed” result.
        Any Structural Damage results also breech the bunker and create a 1” hole. Weapons can be fired through this opening and enemy models can enter by this route. The interior of the bunker is no longer considered to be air-tight.

Shooting at Firing Ports.
        Firing ports or slots are found on vehicles and bunkers. They may also be found on buildings that a unit has had time to prepare as a position. The latter type of building may still have normal sized windows that can be fired on so firing ports are not usually a concern unless trying to target a particular individual.

        Firing ports are usually only a couple of inches across so are very small targets and subject to the following rules if fired upon.

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