ND/Fortification Math

This is some thinking on the design and costs of Fortifications, Roads and Bridges, and other fixed objects.

### Garrison Space

It takes 30-50 sqft of space to house 2 infantry soldiers

minimum is a 2' wide, 6' long bunk with 2' of space to the next cot and 2' of walk space at the foot of the cot. Bunks are stacked 2 high.
reasonable is a 2.5', 6' bunk with 2' of space to the next cot and ~3' of walk space at the foot of the cot.
maximum is is a 2.5', 6' bunk with 2' of space to the next cot and ~5' of walk space at the foot of the cot. Some of this space might be repurposed for other things (eating spaces, armories, etc).
Cavalry stables require 12'x16' (a 12'x12' stall and 4' for walk space in front of it, 200 sqft) per horse and cannot have more than 1 level.

In all cases, add the width of the walls to the length of the walls to account for corners. (ie, a square tower with 10' walls requires 4 walls, 35' by 36', and has a footprint of 45' by 45'.)

## Typical Construction

### Simple Stronghold

45' Square Tower with 10' walls: 3300 tons, $4.53M
Frestanding small stable with brick stronghold walls: 1825 tons, $0.25M
130' square perimeter walls, 12' tall: 3500 tons, $1.56M
Houses 120 + 20 horses, $6.34M

### Basic Castle

6 long barracks, brick stronghold walls, 1 long wall against a curtain wall: 250 tons each, $1.5M
4 Large stables, brick stronghold walls, 1 long wall against a curtain wall: 750 tons each, $3M
7 45' square towers with 10' walls (one at each corner, one in the middle of each long wall, one is a gatehouse): 3300 tons each, $31.71M
2 curtain walls, 150', and 2 curtain walls, 600', all 30' tall: 4000 and 16000 tons, $40M
Houses 1200 + 200 horses, $76.21M

### Military Road

Per mile.

Hole: 1' deep ditch, 14' wide, 5280' long: $7.5K
Bed: 10" of packed earth, 14' wide, 5280' long: $630K
Gravel: 1" of rubble, 14' wide, 5280' long: $285K
Curbs: 2x 4" by 4" of packed earth, 5280' long: $12K
Total is $940K per mile.

### Imperial Highway

Per Mile

Hole: 3' deep ditch, 25' wide, 5280' long: $40K
Base: 1.5' of packed earth, 25' wide, 5280' long: $2M
Bed: 1' of rubble, 25' wide, 5280' long: $6M
Surface: 6" of brick, 25' wide, 5280' long: $3M
Curbs: 2x 4" by 4" of brick, 5280' long: $50K
Total is $11.1M per mile.

### Short Bridge

600' long, spans 400', 12 arches, rises 30'.

4 20' deep by 20' square holes: $1.6K each, 6.4K total.
8 30' deep by 20' square holes, underwater: $8K each, $64K total.
4 pylons, 20' square and 35' tall: $950K and 4500 tons (1660 HP) each, $3.8M total.
8 pylons, 20' square and 100' tall, half underwater: $8.1M and 13000 tons (2350 HP) each, $65M total.
18 half-arches (triangles), roughly 20' wide, 10' tall, and 20' long, concrete: $240K each, $4.3M total
Road surface: 6" of brick, 20' wide, 620' long: $3M
Total is $81.5M.

### Long Bridge

900' long, spans 700', 24 arches, rises 50'.

4 20' deep by 20' square holes: $1.6K each, 6.4K total.
8 30' deep by 20' square holes, underwater: $8K each, $64K total.
12 40' deep by 20' square holes, underwater: $12K each, $144K total.
4 pylons, 20' square and 35' tall: $950K and 4500 tons (1660 HP) each, $3.8M total.
8 pylons, 20' square and 100' tall, half underwater: $8.1M and 13000 tons (2350 HP) each, $65M total.
12 pylons, 20' square and 125' tall, half underwater: $10M and 16000 tons (2550 HP) each, $120M total.
42 half-arches (triangles), roughly 20' wide, 8' tall, and 15' long, concrete: $144K each, $6M total
Road surface: 6" of brick, 20' wide, 930' long: $4.5M
Total is $200M

## Magic

Control Earth can be used to help build a castle.

Time to lift is the amount of time it takes to move a max weight of stone 10 yds vertically and 10 yards horizontally (representing moving from a random outcrapping to the top of a wall).

These build times depend on the castle being built on a stone quarry or equivalent, with stone being supernaturally pulled from the ground and moved immediately into the walls. Assuming the spellcaster's wages of $60K/month, a Good quality spellcasting unit reduces the cost of a simple castle by 95%.

If a castle is built on defensible position without an excellent source of rocks underneath it, spellcasters can speed quarrying without approaching these speeds. A unit of Good quality or better spellcasters devoted to building a castle quadruples the effectiveness of any money spent on building the castle that month, exclusive of the cost of the spellcaster.

*Example*: A modern fortress has a minimum build time of 12 months and costs $100M. Normally, a builder would spend $8.5M/month for 12 months to build a fortress. For $2.06M/month, the same fortress can be built in 12 months for total of $26M.
## Rules

Build times are based on spending $1M a month.

Extra capacity increases cost by 50% for each increase of base capacity (ie, a Modern Fortress that houses 3600 costs $200M). Reduced capacity costs 70% of normal for half capacity, 50% of normal for quarter capacity.

Increasing DB increases costs by 50% per DB increase. Calculate this after calculating the cost for increased or reduced capacity.

Fortifications are usually purchased on a month to month basis. Each man-month of labor costs $0.5K. A modern citadel with a completion date of 7 years costs $2.15M per month for 84 months or $10M for 18 months.