CONSTRUCTION AND SIEGE

UNDERGROUND CONSTRUCTION

As Dungeon Master, you will be interested in the subject of dungeon building for two reasons. 

Most important is the work which will take place in various underground settings you devise for your players. Work will probably be in progress prior to their venturing into the labyrinth, during the course of their adventures therein, and even after they have moved on to some other project or task. 

Later, high level player characters will build their own strongholds, and they will desire some dungeon mazes thereunder.

Although the volume of material given herein is by no means that of a text on mining, it should be more than adequate for quick and easy handling of the task in your campaign.

Multiple Workers. For game purposes, assume that each extra miner will cause an appropriate additional volume of rock to be mined, providing that there is room in the shaft. Assuming that a typical shaft will be 10 ft. wide, and arched to a 16 ft. (or so) peak, including scaffolding, where appropriate, the maximum number of miners, by race, per 10 ft. wide shaft is shown below; increase the number for wider or narrower shafts accordingly, although any miner larger than man-sized needs a 10 ft. minimum width in which to work.

Multiple Shifts. There is no reason to limit work to one-third of the day. If there is need, construction can be carried on 24 hours per day, as long as there are enough fresh workers every 8 hours to do so. No worker may toil more than 8 hours per day.

Natural Area. Where natural passages and cave/cavern space exists, there can be no work, or minor work only to straighten, enlarge, or whatever. Computing the amount of rock necessary to be mined for such passages or spaces is no great matter. The existence of such natural areas is another matter altogether. You can always assume that the basically subterranean races of creatures discover such natural cave areas and select them purposely. For player characters, you might wish to allow the following chances for finding a natural cave area:

The size of such natural areas will typically be small to very large, and with many passages in the case of limestone only. Igneous rock areas will be short passages or small caves only. Lava area spaces will tend to be tubes, often fairly large and long. Other sedimentary areas will be smallish and not extensive.

General Note. As a rule, player characters will not be able to get races of creatures such as kobolds, hobgoblins, orcs, gnolls, ogres, and giants to perform mining labor. These creatures would far rather steal, rob, and kill for their income. Fear of enslavement will sometimes prove successful for a time, but guarding the unwilling miners, and the hard task of getting them to work at their optimum rate will be difficult problems for the taskmaster. 

Miners have tools, which make quite efficient weapons, so one comparable guard per 4 workers is about the minimum. Slave or unwilling labor is from 50% to 80% as efficient, depending on how many foremen are on hand to watch and drive the laborers. If 1:16, efficiency is 50%, if 1:12 it is 60%, 1:8 means 70%, and 1:4 brings efficiency to 80% normal. 

Thus, for every 4 unwilling miners there must be a guard and a supervisor. Of course, if ogres were doing the work, the guard and the task master would have to be equal to ogres in hit dice/power - 4th level fighters or ogres, or comparable, for example.

CONSTRUCTION TIME

Earth Excavation. The cost of the ditch 100 ft. in length, 10 ft. deep, and 20 ft. wide assumes that a crew of 3-4 men work for six weeks. If soil is heavy clay, time will be doubled.

Stone Constructions. Fortress-like stone constructions take about one week per 10 ft. cubic section. Adding 50% to the expenditure will double the rate of construction, but to triple the rate of construction, expenditure must be increased to 250% of the base cost - the maximum increase in construction rate. Normal stone buildings as shown on the cost list, require four months to construct, including interior work. All times assume building materials are on hand. Quarry work and transportation, if any, are additional cost and time factors. Architect costs are also additional.

Wood Constructions. Wooden buildings take approximately one-half the time it takes to construct similar buildings with stone. Wooden hoardings, for example, can be built at the rate of a 10 ft. section per day. 

There are so many variable factors involved that the times given for completion of any given construction must be vague. If you do not wish to spend undue amounts of time calculating, it is suggested that you use the following rough estimates for construction time:

Times assume that an architect has prepared plans in advance, and that normal costs are expended in construction. If additional monies are spent, time is reduced as noted for stone constructions. With respect to walling urban areas, citizens who willingly labor to speed construction will reduce time by 50%.

CONSTRUCTIONS

Arrow slit: Each arrow slit assumes a space behind it in which the bowman stands, ½ ft. w., 4 ft. l.

Arrow slit, crossletted: As the name implies, this is a straight slit with a cross slit for crossbows.

Barbican: The barbican is a solid stone outwork with two 30 ft. diameter by 30 ft. high round towers and a connecting building 20 ft. wide by 30 ft. long by 20 ft. high. It must be properly pierced and battlemented. The barbican can include a gate or can be a simple outwork.

Bartizan: This is a small tower built to provide flanking fire on curtain walls or as an additional firing platform.

Batter, plinth or splay: These terms describe a sloping support which strengthens wall or tower bases, hindering attack by machine or humans.

Battlement: These are the parapet (or sill), embrasures, and merlons set atop a wall to provide cover for bowmen. If the surface is not broad, a catwalk (q.v.) must also be constructed. A 14 ft. section of battlement will typically have two 4 ft. wide merlons and two embrasures 3 ft. wide.

Building, stone: This is a single course (1 ft. thick) of dressed or field stone with 120 ft. of outside walls 20 ft. high, with two wooden floors (second and attic), two flights of stairs, a peaked roof, and one wooden door. Cellar excavation, ground flooring, windows, interior walls, and additional doors are extra. The cost to increase wall thickness is 10% of initial cost per course of stone (1 ft. thickness). Thus, the building upgraded to 10 ft. thick walls (and appropriate outer dimensions) would cost 500 g.p. plus 90%, or a total of 950 gold pieces. The cost of a stone building can be used for  computing interior dungeon walls.

Building, wood: This is the same as stone building above, but walls are framed with planks, total thickness ½ ft.

Buttress, stone: This is a wall support generally used for reinforcing the outside surface of a curtain wall, tower, etc. To buttress a wall up to 20 ft. height, the equivalent of three buttress sections is needed.

Catwalk: This is a sturdy platform about 3 ft. wide which is built upon a wall or palisade to enable defenders to shoot or fight over the top of the construction.

Ditch: This is a trench excavated as an obstacle, with sloped, compacted, and sodded sides. If a rampart of earth is built immediately above one side of a ditch the cost of the rampart is only 20% of the amount shown. The cost of ditching can be used for computing the cost of excavating for cellars, basements, dungeons, etc.

Door, iron: An iron door is typically set into stone with three long hinges/supports. It consists of plates about one inch thick bolted to a frame about one-half that thickness. The cost of larger or smaller or thicker doors is 2 g.p./sq. ft. of one-half inch iron added to or subtracted from the basic door cost. It has an iron bar on one side.

Door, secret: This is a stone portal which operates by counter-poise or pivot, with a hidden mechanism to trigger operation. There is no reduction for smaller portals, and the cost for larger ones is 5 g.p. per square foot of increased size.

Door, trap: This is a stout wooden door about two inches thick set into a floor. It is raised by an iron ring which is constructed as part of the trap door. Each additional square foot of trap door costs 1 s.p.

Door, wooden: This is a sturdy door of hardwood (maple, ash, etc.) about three inches thick. A square foot of additional wood (or for less wood) in the door is 2 s.p. The door is barred on one side by a two-by-four.

Door, wooden, reinforced: This is a stout oaken door, four inches thick, bound with iron bands and secured by a 3 x 6 oaken bar. Each square foot of alteration is valued at 5 s.p.

Drawbridge: This is a bridge of six-inch thick hardwood planks bound with iron and attacked to great chains which pass through the wall of the stronghold. These chains are used to raise the drawbridge by means of a winch and capstan bars and held fast by pawl and ratchet. Each 1 square foot alteration is valued at 2 g.p.

Embrasure shutters: These wooden pieces mask an embrasure. They are constructed in two sections, independent of each other, which rest firmly against the merlons on either side but swing out from the bottom to allow archery.

Gatehouse, stone: A gatehouse is a building of stone with walls 5 ft. thick, two reinforced doors guarding a portal 10 ft. wide by 12 ft. high, a portcullis, and machicolated battlements atop the structure. It is 30 ft. high to the battlement; the battlement is 7 ft. high. The gatehouse has 140 ft. of outer walls. Two barbettes cover its gate side.

Hoardings, wooden: This is a very stout wooden catwalk projecting in front of a wall. It has embrasures, a peaked roof connecting it to the battlement, and holes in the flooring to enable defenders to hurl and discharge missiles at attackers at the wall foot.

Machicolation, stone: This is a stone projection which moves the battlement out over the outer face of the wall. It has spaces in the stone flooring which allow missiles to be discharged to the space at the wall foot.

Merlon: A stone section rising above the parapet to provide cover for defenders atop wall or tower is a merlon. The merlon can be pierced with a slit for additional missile power.

Moat: A water-filled ditch (properly packed and graveled in most cases) comprises a moat.

Murder hole: This is a slit, crossletted slit, or similar opening in a floor to command a passageway below. In combination with inner portcullis, inner wall slits, and pits, they make an entrance passage in a gatehouse or  similar structure very unhealthy for attackers.

Palisade: A wooden fence of logs about six inches thick sunk into the ground from 4 ft. to 6 ft. forms a palisade. A palisade is usually built atop a rampart and equipped with a catwalk in order to turn the upper portion into a parapet.

Parapet, stone: This is a low stone wall 3 ft. high and 3 ft. thick (or deep) to provide cover for defenders. It is crenelated by placement of merlons.

Pilaster: This is a pillar-like reinforcement about as thick at its base as at its top.

Pit: A pit is a hole covered by a wooden or metal lid. The lid is removed when attackers threaten the work in which it is in. A pit is typically walled and floored with finished stone.

Portcullis: This is a grille of reinforced wooden or iron bars which is raised and lowered by counter-weights and winch. For each square foot of alteration adjust the cost by 2 gold pieces.

Rampart, earth: A rampart is a layered, packed, and sodden earthen wall, usually topped by a palisade. (See also ditch.)

Stairs, stone: Solid stone for the first 10 ft. rise, the stone staircase must be buttressed if it rises beyond 10 ft.

Staircase, wooden: Typical stairs are built of sturdy hardwood. 

Tower, round: A stone cylinder, without doors, arrow slits, or battlements, a round tower has one stone floor, a flat stone roof, and spiral stone stairs to the roof. The walls of 20 ft. diameter towers are 5 ft. thick, those of a 30 ft. diameter tower are 6 ft. thick, and those of a 40’diameter tower are 7 ft. thick.

Tower, square: See tower, round above. A 10 ft. square tower has walls 3 ft. thick.

Tunnel, underground: A straight shaft generally used as an escape route, the underground tunnel is assumed to be dug through soft earth and floored, walled and roofed in rough stone. If it is dug through hard earth the cost will increase by 100%. If the tunnel is mined through solid rock, the cost will be 500% of the figure shown.

Wall, bastion: This is a curved wall section, typically hemispherical, built into a curtain wall to provide flanking fire. It has no battlement.

Wall, curtain: This is a straight wall section without battlements. If it is built above 20 ft. height it must be thickened or supported by buttresses, pilasters, etc.

Window, shuttered: A typical opening in a wall, it is covered by wooden shutters of one inch thickness.

Window, shuttered barred: This is a typical window protected by a single bar with spurs to either side to prevent entrance through its aperture. Bars on wider windows can be multiples of the type above or crossbar grilled.

Siege Engines and Devices of War

Occasionally the need to handle various siege equipment and artillery will arise. While the conduct of large scale battles is not a subject for this work, the 1:1 use of such machines can be dealt with easily herein.

Ballista: A war engine which fires a heavy, spear-like missile. The cost of missiles for a ballista is comparable to javelin cost (5.3.2).

Catapult: An engine operating by tension or torsion which hurls heavy missiles. Combustibles, rocks, dead animals, barrels of sewage, etc. can be used as ammunition.

Cauldron, suspended: A huge iron pot for boiling or flaming liquid. It is suspended in such a manner so as to allow it to be tipped easily in order to spill its contents on attackers.

Gallery, covered: A sometimes movable construction, typically a heavy timber frame, with green hides protecting the wood. It has a double roof, one peaked to shed missiles and liquids. It is used to provide cover for attackers operating against a wall. Width is 12’, height 12’, length 20’.

Hoist: A frame with fulcrum and lever, the lever equipped at one end with a basket which can hoist up to 4 attackers to a height of 30 ft. to assault a construction.

Mantlet, movable: A wooden wall, with wheels for movability, and a slit for archery. It is typically 6 ft. wide, 8 ft. long, and several inches thick. The mantlet is slanted backward at a slight angle.

Ram: A movable gallery equipped with a heavy log suspended from two roof beams by chains. The log is shod in iron and used to batter through defenses.

Ram catcher: A fork or hook of iron on a long pole. It is lowered by defenders to catch and hold a ram (or sow) at work on a wall. The defenders then raise the catcher to disable or break the ram.

Siege tower: A mobile wooden tower, typically a beam frame with slats and green hides to protect it from fire. It is 16 ft. square at the base, 40 ft. high, with a 10 ft. square parapet at the top. At 30 ft. height there is a drawbridge 10 ft. square. The lower portion is for locomotion. A ladder leads up the back or interior to drawbridge deck and the upper parapet, with two intermediate floors.

Sow: A pick/screw device, otherwise conforming to the ram, for use against stonework.

Trebuchet: A large siege engine which fires very heavy missile loads a great distance by means of lever and counterpoise.

WAR MACHINE FIRE TABLES

Use the tables below to determine “to hit” probabilities whenever siege engines/war machines fire:

* Damage possible only if victim is directly in front of the boom device (ram, pick, or screw).

Range is the distance from engine to target creature. The trajectory of ballista missiles is basically a flat one, while those from catapults and trebuchets have a high arch. 

Minimum range basically reflects arching trajectory. The range for rams and sows is only the maximum swing of the boom and indicates the proximity of the engine housing to target (normally a construction).

Damage variable is self-explanatory. 

Rate of fire can be achieved only with at least a minimum crew. If less than the minimum number of crewmen are available, then rate of fire drops to at best 50% of normal. The maximum number of crew enables a ballista to double its normal rate of fire. All other engines gain nothing (except less chance of dropping below minimum requirements for normal rate of fire) by having crew above minimum numbers shown.

Hit Determination

Artillerists must operate all missile engines in order to allow them a chance to hit. (You may, at your option, allow fighters to opt to learn various artillery engines in lieu of normal hand weapons.) 

The level of the crew chief determines the chance “to hit”, i.e. if a 0-level fighter, then the first column, if a 1st or 2nd level then the second level, etc. 

• All targets, regardless of actual Armor Class are considered as AC 0 for purposes of “to hit” determination, except for ballista targets which are always considered to be AC 10 if exposed to sight.

If a direct hit is scored, determine damage according to target size.

I. Direct Fire Machines: ballistae, mangonels, scorpions;

II. Indirect Fire Machines: catapults, onagers, trebuchets

Adjust the base number “to hit” by using the following tables of modifiers. Roll d20, and if the number equals or exceeds the adjusted base number, a hit has been scored.

If a catapult or trebuchet miss occurs, go to the Grenade-like Missiles section to find where the missile struck. Misses will always pass over, to the left, to the right, or fall short of the closest appropriate part of the target, even if this causes the missile to fall short or exceed the minimum or maximum range restrictions.

As noted in the Grenade-like Missiles section, missiles from small catapults are considered to be of 1 ft. diameter, those from trebuchets, 2 ft. 

Ballista missiles are akin to spears.

Field Of Fire. The arc of fire of missile engines is as follows:

Intervening objects will not be likely to interfere with the flight of arched missiles from catapults or trebuchets, unless they impose themselves near the engine or the target. Thus, a trebuchet could arch its missile over a 40 ft. high wall which was more than 6” distant from it and less than 6” from the target. As ballista missiles are on a flat trajectory, objects between the engine and the target will interrupt the flight path of these missiles.

Cover. Target creatures which can be seen only partially or which are totally unseen cannot be hit by catapult or trebuchet missiles in the normal manner. A target area must be named and the Grenade-like Missiles determination is then used to find where the missile actually hits. Ballista fire is not possible when target is unseen. If they are partially visible, use the Missile Fire Cover And Concealment Adjustments.

Siege Damage. The damage caused to constructions by the various engines, as well as that caused by various monsters and spells, is detailed under Siege Attack Values.

SIEGE ATTACK VALUES

*  Damage shown is per round of attack by this mode. 

** Damage shown is per level of the spell caster employing the spell, and assumes fire damage following; If the wooden target is protected by green hides, is wet, etc., reduce damage by 50%. 

† Damage inflicted only if sow is equipped with a screw device.

Soft stone includes fired brick, limestone, sandstone. 

Hard rock is granite and similar material.

[Campaign Rules.]

Using melee weapons against constructions is typically useless. However, some consideration is given based on the type of weapon and the material it is being used upon.

Wooden Barriers (e.g. wood doors). Against doors made primarily of wood (no iron plating), an axe-type of weapon will do 0.5 structural points of damage for every blow that does, at minimum, 10 hit points of damage. If damage done is less than this, no structural damage occurs (although cosmetic damage is done). Pole arms with axe-heads and battle axes receive a +4 bonus on this damage (A door's AC is 10; No base armor rating) and most doors will be treated as Large sized. Note that weapons must have the required space to operate effectively.  

Wooden Containers (e.g. wood chests). Against stout containers made primarily of wood (no iron plating), an axe-type of weapon will require the item to save vs. Crushing Blow for every blow that does, at minimum, 10 hit points of damage. If damage done is less than this, then a save vs. Normal Blow is made. Pole arms with axe-heads and battle axes receive a +4 bonus on this damage (A container's AC is 10; No base armor rating; Damage by the weapon is based on the size of the object). Reinforced wooden containers (like chests) will receive a bonus of +3 on saving throws vs. blows by melee weapons. Note that weapons must have the required space to operate effectively.  

Soft Stone Barriers (e.g. bricked walls). Against barriers made primarily of soft stone and not more than about a 1 foot in thickness, a pick-type of weapon will do 0.5 structural points of damage for every blow that does, at minimum, 10 hit points of damage. If damage done is less than this, no structural damage occurs (although cosmetic damage is done). Military picks receive a +4 bonus on this damage (A wall's AC is 10; No base armor rating) and most barriers will be treated as Large sized. Note that weapons must have the required space to operate effectively.

[...]

Additional Attack Forms

Mining assumes that a tunnel will be driven under a construction, shored up, filled with combustibles, and then fired so as to burn out supports. If successful, this will breach a 10 ft. wide section of curtain wall or cause 10 points of damage to other sorts of constructions.

Sapping assumes that workers, under protection of a gallery, for example, are able to dig away at earth or stone. This mode of attack is slow. To represent it, give it the damage done by a sow, but on a per turn, rather than per round, basis.

It is important that the reader understand that all values are representative only. The entire process of siege warfare would prove interminable in a campaign, so it has been speeded up here to force sallies and counter attacking or the fall of the fortress.

CONSTRUCTION DEFENSIVE VALUES