Underground Construction


Multiple Workers
Multiple Shifts
Natural Areas
General Note
Construction & Siege

As DM 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.


                                                                                                                                                                                                              Type of Rock Being Mined
Race of Miner Working Very Soft Soft Hard
gnoll, [halfling], [human] 75' 50' 25'
[gnome], [kobold] 80' 60' 30'
[goblin], [orc] 85' 65' 30'
[dwarf], [hobgoblin] 90' 70' 35'
[ogre] 150' 100' 50'
[hill giant] 250' 150' 75'
[fire giant], [frost giant] 300' 200' 100'
[stone giant] 500' 350' 175'

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'
wide, and arched to a 16' (or so) peak, including scaffolding, where appropriate,
the maximum number of miners, by race, per 10' wide shaft is
shown below; increase the number for wider or narrower shafts
accordingly, although any miner larger than man-sized needs a 10' minimum width in which to work.
Race Max. Number Per 10' Wide Shaft
[dwarf], [gnome], [goblin], [halfling], [kobold] 16
[hobgoblin], [human], [orc] 12
gnoll 8
[ogre] 6
[giant], any type 4

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 PCs, you might wish to allow the
following chances for finding a natural cave area:
Type Of Rock Being Mined Chance for Natural Space
limestone (very soft) 1 in 10
other sedimentary rocks (soft) 1 in 50
lava (hard) 1 in 20
other igneous rocks (hard) 1 in 100

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 1 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.

Originally Posted by Patryn of Elvenshae


So, how "realistic" were those numbers from way back in the day? Is it something you made up to fit the kind of milieu you wanted, or did you first base the human mining rate off of research, and then modified accordingly? A combination of both?

Enquiring minds want to know!

Thanks in advance,


Well, although I do have ancestors that were Cornish miners, I didn't consult them when I did the table in the OAD&D DMG. Basically, it was a bit generous for hard-rock mining, about correct for softer sedimentary stone...I believe <nervous laugh>