Foundation Types

Part of Permanent Shelter

There is no single “best” foundation. The right choice depends on what materials you have, what soil you are building on, and how much labor you can invest. This guide covers the four most practical foundation types for building without modern tools or materials, with detailed instructions for each.

Comparison at a Glance

Foundation Type	Best For	Durability	Effort	Materials Needed
Stone pier	Uneven terrain, most climates	50-100+ years	Medium	Flat stones, gravel
Continuous stone	Heavy structures, cold climates	100+ years	High	Large quantity of stone, possible mortar
Post-in-ground	Forested areas, quick builds	5-15 years (untreated), 20-30 (charred)	Low	Straight timber, digging tools
Earthen pad	Dry climates, flat terrain	20-50 years	Medium	Clay-rich soil, gravel

Stone Pier Foundation

Individual stone columns placed at load-bearing points — corners, wall intersections, and at intervals along walls.

When to Use

• Uneven or sloping ground (piers can be different heights to create a level top)
• Limited stone supply (uses far less stone than continuous foundations)
• Structures with wooden sill beams

Build Instructions

Materials: Flat stones 30+ cm across, gravel, smaller wedge stones.

1. Lay out pier positions. Mark each corner and every 1.5-2 m (5-7 ft) along wall lines.

2. Dig holes 45-60 cm deep (18-24 in), wider at the bottom. In cold climates, dig below the frost line.

3. Add 15 cm (6 in) gravel base. Tamp firmly.

4. Place the footing stone — your widest, flattest stone. It should be at least twice the width of the wall above.

5. Stack stones upward, selecting each for maximum contact with the stone below. Use thin wedge stones to eliminate rocking. Each course should be slightly narrower than the one below.

6. Level all piers to the same height using a water level. Adjust by adding or removing stones.

7. Cap each pier with a wide, flat stone that overhangs the pier by 5-8 cm on all sides. This “drip cap” sheds water away from the pier.

The Drip Cap

A flat capstone wider than the pier prevents rainwater from running down between the stones. This single detail can double the life of a stone pier foundation.

Common Failures

• Piers leaning outward from wall pressure — use wider base stones
• Sill beam rotting on pier tops — add a bark moisture barrier between stone and wood

Continuous Stone Foundation

An unbroken wall of stone running the full perimeter of the building, rising from below ground level to above grade.

When to Use

• Heavy masonry or stone walls above
• Cold climates where a full perimeter frost barrier is needed
• Structures intended to last generations
• Basements or root cellars beneath the structure

Build Instructions

Materials: Large quantity of stone (roughly 1 cubic meter per running meter of wall), gravel, lime mortar if available.

1. Dig a trench the full perimeter, at least 60 cm wide (24 in) and deep enough to reach below the frost line. Make the trench bottom flat and level.

2. Lay a gravel drainage bed — 15-20 cm (6-8 in) of gravel, tamped flat.

3. Place the first course. Use your largest, flattest stones. They should span the full width of the trench. This is the footing course and bears the most weight.

4. Build upward course by course. Each stone should bridge the joint between two stones below (running bond pattern). This interlocking pattern prevents vertical cracks from propagating.

5. Fill the core. If your wall is wider than a single stone, fill the center with smaller stones packed tightly, not loose rubble. Loose fill creates weak points.

6. Build to 20-30 cm (8-12 in) above finished grade. This keeps wooden wall components well above splash-back from rain.

7. Backfill against the outside with gravel, not soil. This creates a drainage layer that pulls water away from the foundation wall.

The Running Bond is Not Optional

Stacking stones in columns (one directly above another) creates vertical weak lines. A single frost heave or lateral pressure will split the wall along these lines. Always overlap joints — each stone should cover the gap between two stones below.

Time Investment

A continuous stone foundation for a 4 x 6 meter shelter (13 x 20 ft) typically requires 2-3 weeks of work for two people, including stone gathering.

Post-in-Ground Foundation

Vertical timber posts set directly into holes in the ground, supporting the structure above.

When to Use

• Abundant straight timber available
• Limited stone supply
• Speed is critical (fastest foundation type)
• Elevated structures in wet or flood-prone areas

Build Instructions

Materials: Straight posts 15-25 cm diameter (6-10 in), gravel, charcoal or fire.

1. Select posts. Choose the most rot-resistant species available: cedar, locust, oak heartwood, or larch. Avoid pine and poplar — they rot within a few years.

2. Char the buried portion. Build a small fire and slowly char the bottom third of each post to a depth of 3-5 mm. This carbonized layer resists rot and insect damage. Do not burn through — you want blackened, hardened wood, not ash.

3. Dig post holes 60-90 cm deep (24-36 in), roughly twice the post diameter. Below the frost line in cold climates.

4. Add 10 cm (4 in) gravel at the bottom of each hole for drainage.

5. Set the post plumb (perfectly vertical). Check from two perpendicular directions.

6. Backfill in layers. Alternate 15 cm layers of gravel and tamped soil. Gravel drains water away from the post; tamped soil holds it firm.

7. Brace temporarily until the structure above locks the posts in position.

Post Treatment	Expected Life in Ground
Untreated softwood	3-5 years
Untreated hardwood	7-12 years
Charred softwood	10-15 years
Charred hardwood	20-30 years
Charred + gravel-packed	25-35 years

The Gravel Collar

Pack 10 cm of gravel around the post at ground level instead of soil. This is where rot is worst — the alternating wet/dry zone right at the surface. Gravel keeps this zone drained and extends post life significantly.

Replacement Plan

Post foundations are not permanent. Plan for eventual post replacement by designing your structure so that posts can be jacked up and swapped without dismantling walls. This means keeping posts accessible, not buried inside walls.

Earthen Pad Foundation

A thick platform of compacted earth (often rammed earth or packed clay) that the entire structure sits on.

When to Use

• Dry climates with minimal rainfall
• Flat terrain
• No stone or timber available for other foundation types
• Single-story lightweight structures

Build Instructions

Materials: Clay-rich subsoil, gravel, water, a tamping tool (heavy flat stone or log).

1. Excavate the building footprint to a depth of 30-45 cm (12-18 in). Make the excavation 30 cm wider than the building on all sides.

2. Lay a gravel base — 10-15 cm (4-6 in) of gravel across the entire excavation. This is your moisture barrier.

3. Prepare the earth mix. Ideal mix is roughly 70% clay-rich subsoil, 30% sand or fine gravel. Too much clay cracks when drying; too much sand crumbles. Test: a handful should hold its shape when squeezed but not feel sticky.

4. Place and compact in layers. Add the earth mix 10 cm at a time (4 in). Moisten each layer — damp, not wet. Tamp every square centimeter until the tamper bounces rather than sinks.

5. Build up to 15-20 cm (6-8 in) above surrounding grade. This elevation prevents surface water from flooding the pad.

6. Allow to cure. Let each layer dry partially before adding the next. The completed pad needs 1-2 weeks of dry weather to fully harden.

7. Apply a surface treatment. A thin layer of lime wash or animal fat mixed with ash creates a water-resistant surface skin.

Earthen Pads and Rain

An earthen pad foundation will erode in sustained wet weather if unprotected. You must have wide roof overhangs (at least 60 cm / 24 in) and maintain the surface treatment annually. In climates with more than 75 cm (30 in) of annual rainfall, choose a different foundation type.

Hybrid Approaches

In practice, you may combine types:

• Stone piers with earthen infill — Piers at load points, packed earth between them to block wind and pests from under the structure.
• Post foundation with stone footings — Set posts on flat stones rather than directly in soil. The stone prevents the post bottom from sitting in standing water.
• Continuous stone perimeter with earthen pad floor — Stone walls below grade for durability, compacted earth inside for a solid floor surface.

Key Takeaways

• Match your foundation to your materials and climate — do not force a design that your environment cannot support.
• Stone pier is the most versatile choice for beginners with access to stone.
• Continuous stone is the most durable but requires the most labor and material.
• Post-in-ground is the fastest to build but has the shortest lifespan — always char and gravel-pack your posts.
• Earthen pad works well in dry climates but fails in wet ones without aggressive water management.
• Hybrid foundations are not cheating — they are smart engineering that uses each material where it performs best.
• Drainage is universal — every foundation type needs gravel beneath it and water directed away from it.