Sovereignty Module: Set the Stone
Complete Masonry, Stone Construction, and Lime Mortar Guide
The Philosophy of Stone
Stone is the most permanent building material available to humanity. Stone structures built by the Romans still stand after 2,000 years. Stone requires no maintenance, does not rot, does not burn, and gains character with age. Unlike timber (which requires large trees and decades of growth), stone is available almost everywhere and requires only knowledge and labor to transform into buildings, walls, bridges, and infrastructure that will outlast every other material. This campaign covers stone selection, cutting, laying, and the production of lime mortar.
Chapter 1: Stone Types and Selection
| Stone Type | Hardness | Workability | Strength | Best Use | Examples |
|---|---|---|---|---|---|
| Granite | Very hard | Difficult | Excellent (compressive) | Foundations, bridges, monuments | Pink, grey, black granite |
| Limestone | Medium | Good | Good | Walls, arches, carving | Portland stone, Indiana limestone |
| Sandstone | Soft-medium | Easy | Moderate | Walls, paving, carving | Brownstone, flagstone |
| Slate | Medium | Splits easily in one plane | Good (in compression) | Roofing, flooring, counters | Welsh slate, Vermont slate |
| Basalt | Very hard | Difficult | Excellent | Foundations, road paving | Dark grey/black volcanic |
| Marble | Medium | Good | Good | Decorative, flooring, carving | White, veined varieties |
| Fieldstone | Variable | Used as-found | Variable | Rubble walls, foundations | Any glacially deposited stone |
Selection Criteria:
| Criterion | Test | Good Result | Poor Result |
|---|---|---|---|
| Durability | Soak in water 48 hours, freeze, thaw, repeat 5x | No cracking or flaking | Spalling, crumbling |
| Absorption | Weigh dry, soak 24 hours, weigh wet | Less than 5% weight gain | More than 8% (will frost-damage) |
| Bedding planes | Examine for layers/grain | Visible, consistent layers | Random fractures (unpredictable splitting) |
| Ring test | Strike with hammer | Clear ringing tone | Dull thud (internal cracks or soft spots) |
| Hardness | Scratch with steel | Steel leaves no mark (hard) | Steel scratches easily (too soft for structural) |
Chapter 2: Quarrying and Shaping Stone
Splitting Stone (using natural bedding planes):
- Identify the grain/bedding direction (stone splits easiest along these planes)
- Drill or chisel a line of holes along the desired split line (4-6 inches apart)
- Insert feathers and wedges (two thin metal shims with a wedge between them) in each hole
- Tap each wedge in sequence (light, even taps across all wedges)
- Repeat the sequence until the stone splits along the line
Shaping Stone (dressing):
| Tool | Use | Finish Quality |
|---|---|---|
| Point chisel | Rough shaping, removing large bumps | Rough (pitched face) |
| Tooth chisel (claw) | Intermediate shaping | Medium (tooled face) |
| Flat chisel | Final smoothing | Smooth (dressed face) |
| Bush hammer | Texturing flat surfaces | Uniform rough texture |
| Mallet (wooden or iron) | Driving chisels | N/A (striking tool) |
| Pitching tool | Removing large waste along a line | Rough edge |
Finish Types:
| Finish | Method | Appearance | Use |
|---|---|---|---|
| Quarry face (natural) | As split from quarry | Rough, natural | Rubble walls, rustic |
| Pitched face | Edges trimmed with pitching tool | Rough face, clean edges | Ashlar walls (rustic) |
| Tooled | Dressed with tooth chisel | Parallel grooves | Formal walls |
| Smooth (rubbed) | Ground with abrasive stone | Flat, smooth | Fine architecture |
| Polished | Progressive grinding to mirror finish | Reflective | Monuments, counters |
Chapter 3: Lime Mortar
Why Lime (not Portland cement):
| Property | Lime Mortar | Portland Cement Mortar |
|---|---|---|
| Flexibility | Moves with building (self-healing micro-cracks) | Rigid (cracks transfer to stone) |
| Breathability | Allows moisture to pass through | Traps moisture (causes stone decay) |
| Strength | Weaker than stone (sacrificial) | Stronger than some stone (damages stone) |
| Repair | Easy to remove and repoint | Difficult, damages stone during removal |
| Lifespan | Centuries (if maintained) | 50-100 years |
| Production | Low-tech (limestone + fire) | High-tech (requires industrial kiln) |
Making Lime:
- Burning limestone (calcination): Heat limestone (calcium carbonate, Cite) to 900C+ in a kiln for 24-72 hours. This drives off CO2, producing quicklime (calcium oxide, CaO). The limestone must glow orange-red throughout.
- Slaking (hydrating): Add water to quicklime carefully (EXOTHERMIC, produces extreme heat and steam). The quicklime absorbs water and crumbles into a fine powder (hydrated lime, calcium hydroxide). Or add excess water to produce lime putty (preferred for mortar).
- Aging: Lime putty improves with age. Store submerged under water for minimum 3 months (traditionally 1-3 years). Older putty is more workable and produces better mortar.
Lime Mortar Recipe:
| Component | Ratio (by volume) | Purpose |
|---|---|---|
| Lime putty (or hydrated lime) | 1 part | Binder |
| Sharp sand (angular, well-graded) | 2.5-3 parts | Aggregate (provides bulk and strength) |
| Water | As needed for workability | Hydration |
Mix thoroughly. Mortar should be plastic (holds its shape when squeezed) but not runny. Use within 2-3 hours of mixing (or cover to prevent drying).
How Lime Mortar Sets:
Lime mortar does not "dry" like Portland cement. It carbonates: absorbs CO2 from the air, slowly converting back to calcium carbonate (limestone). This process takes weeks to months (thick walls may take years to fully carbonate internally). During this time, the mortar must be kept damp (mist regularly) and protected from frost.
Chapter 4: Wall Construction
Rubble Wall (simplest, using uncut fieldstone):
- Dig foundation trench below frost line (12-36 inches depending on climate)
- Fill with large stones and gravel (drainage foundation)
- Begin laying stones: largest at bottom, flat sides up
- Two faces (inner and outer) with rubble fill between (hearting)
- Bond stones (long stones that span the full wall width) every 3-4 square feet
- Fill gaps with smaller stones and mortar
- Keep courses roughly level (use string line)
- Batter (lean inward) slightly: 1 inch per foot of height for stability
Ashlar Wall (cut stone, formal):
- All stones cut to rectangular blocks with flat faces
- Laid in regular courses (rows) with thin mortar joints (3/8 inch)
- Stagger vertical joints (no joint should align with the one above or below)
- Bond pattern: every 5th-7th course should be "headers" (stones turned sideways, spanning wall width)
- Result: strongest, most formal stone wall
Wall Thickness Rules:
| Wall Height | Minimum Thickness | Notes |
|---|---|---|
| Up to 4 feet | 18 inches | Garden walls, retaining walls |
| 4-8 feet | 24 inches | Building walls (single story) |
| 8-12 feet | 30 inches (or tapered) | Two-story buildings |
| 12-20 feet | 36+ inches at base | Large buildings, fortifications |
Chapter 5: Arches and Lintels
The Arch (stone's greatest structural achievement):
An arch converts downward loads into outward thrust, allowing stone (which is strong in compression but weak in tension) to span openings. Every stone in an arch is in compression.
Arch Construction:
- Build a wooden form (centering) in the exact shape of the desired arch
- Support the centering on posts at the correct height
- Lay stones (voussoirs) from both sides simultaneously, working toward the center
- Each voussoir is wedge-shaped (wider at the top/outside)
- The final stone placed at the top center is the keystone
- Allow mortar to cure fully (2-4 weeks minimum)
- Remove centering carefully (the arch is now self-supporting)
Arch Types:
| Type | Shape | Span Capability | Difficulty |
|---|---|---|---|
| Semicircular (Roman) | Half circle | Up to 50+ feet | Moderate |
| Segmental | Less than half circle | Up to 30 feet | Moderate |
| Pointed (Gothic) | Two arcs meeting at a point | Up to 80+ feet | High |
| Flat (jack arch) | Nearly flat (very slight rise) | Up to 6 feet | High (requires precise cutting) |
Lintels (simplest spanning method):
A single stone spanning an opening. Limited by the tensile strength of stone (typically 4-6 feet maximum for most stone types). Must be at least 6 inches deep for every foot of span.
Chapter 6: Foundations
Foundation Principles:
| Principle | Rule | Why |
|---|---|---|
| Below frost line | Dig below maximum frost penetration depth | Frost heave lifts and cracks foundations |
| On undisturbed soil | Never build on fill or recently disturbed earth | Fill settles unevenly |
| Wider than wall | Foundation should be 1.5-2x wall width | Distributes load over larger area |
| Level | Top of foundation must be perfectly level | All errors compound upward |
| Drainage | Gravel bed below and beside foundation | Water is the enemy of all foundations |
Foundation Types:
| Type | Depth | Width | Best For |
|---|---|---|---|
| Strip foundation (continuous) | Below frost line | 2x wall width | Standard walls |
| Pad foundation (isolated piers) | Below frost line | 2-3 feet square | Post and beam buildings |
| Rubble trench | Below frost line | 18-24 inches | Well-drained soils, eco-building |
| Raft (floating slab) | 12-18 inches | Entire building footprint | Poor soils, lightweight buildings |
Chapter 7: Vaults and Domes
The Barrel Vault (simplest vault):
A continuous arch extended in length. Creates a tunnel-shaped ceiling. Requires continuous support along both sides (thick walls or buttresses).
The Groin Vault:
Two barrel vaults intersecting at right angles. Concentrates thrust at four corner points (allowing thinner walls between). The basis of Gothic cathedral construction.
The Dome:
An arch rotated 360 degrees. Creates a hemispherical ceiling. Thrust is distributed evenly around the circular base. Can span enormous distances (the Pantheon in Rome: 142 feet, built 125 AD, still standing).
Corbelling (false arch/dome):
Each course of stone projects slightly inward beyond the one below. Eventually the courses meet at the top. Not a true arch (each stone is cantilevered, not in pure compression) but simpler to build and requires no centering.
Chapter 8: Dry Stone Walling (no mortar)
Dry stone walls use no mortar. They rely entirely on gravity, friction, and the skill of the builder in selecting and placing stones.
Principles:
| Rule | Application |
|---|---|
| Two faces, hearting between | Wall is actually two walls leaning against each other with rubble fill |
| Cross every joint | No vertical joint should continue through two courses |
| Batter inward | Both faces lean inward (typically 1:6 ratio) |
| Through stones every 3 feet | Long stones spanning full width tie the two faces together |
| Large at bottom, small at top | Gravity and stability |
| Coping (cap stones) on top | Flat stones laid on edge protect the wall top from water |
Dry Stone Wall Lifespan: 100-200+ years with minimal maintenance (replacing fallen stones). Many dry stone walls in Britain are 300-500 years old.
Chapter 9: Stone Bridges
Arch Bridge (most durable):
- Build temporary wooden centering spanning the gap
- Construct abutments (massive stone supports at each end) on solid foundations
- Lay voussoirs from both abutments toward the center
- Set keystone
- Fill spandrels (space above arch, below road surface) with rubble and mortar
- Pave road surface
- Remove centering
Span Capabilities:
| Bridge Type | Maximum Practical Span | Example |
|---|---|---|
| Single arch (semicircular) | 100+ feet | Pont du Gard (Roman, 160 feet) |
| Multi-arch | Unlimited (multiple spans) | Most medieval bridges |
| Clapper bridge (flat stone slabs) | 6-8 feet per span | Dartmoor, prehistoric |
| Corbelled bridge | 15-20 feet | Ancient, simple |
Chapter 10: Maintenance and Repair
Repointing (replacing deteriorated mortar):
- Rake out old mortar to depth of 2x joint width (minimum 3/4 inch)
- Brush out dust and debris
- Dampen joint with water (prevents new mortar from drying too fast)
- Press new lime mortar firmly into joint with pointing trowel
- Finish flush or slightly recessed (never proud of stone face)
- Keep damp for 3-7 days (mist regularly)
- Protect from frost for 2 weeks minimum
Common Problems:
| Problem | Cause | Solution |
|---|---|---|
| Bulging wall | Foundation settlement, water behind wall | Rebuild section, improve drainage |
| Spalling stone | Trapped moisture freezing, cement mortar | Replace damaged stones, use lime mortar |
| Cracking | Settlement, thermal movement, overloading | Monitor; if progressive, address cause |
| Efflorescence (white deposits) | Salts migrating to surface | Dry brush off; improve drainage; will diminish over time |
| Plant growth in joints | Seeds in mortar, moisture | Remove plants, repoint, reduce moisture |
Reference Card
MASONRY ESSENTIALS:
- Stone is strongest in compression (pushing together), weakest in tension (pulling apart)
- Lime mortar, not cement (lime is flexible, breathable, repairable, and lasts centuries)
- Foundation below frost line on undisturbed soil (non-negotiable)
- Batter walls inward (1 inch per foot of height for rubble, less for ashlar)
- Bond stones (spanning full wall width) every 3-4 square feet
- Arches convert downward load to outward thrust (need buttresses or thick walls)
- Dry stone walls need no mortar but require skill in stone selection and placement
- Keep lime mortar damp during curing (mist for 7+ days, protect from frost)
This campaign provides the complete knowledge to build permanent stone structures using locally available materials. A community with masonry skills can build houses, walls, bridges, aqueducts, and fortifications that will stand for centuries without maintenance, using the most abundant and durable building material on Earth.