Rammed Earth Wall Calculator
Estimate compacted soil, lime or cement stabilizer mass, and worker-days for a rammed-earth wall from length, height, thickness, and stabilizer percentage.
How this works
Wall volume is computed first; loose subsoil bulks ~30% so we order more raw soil than the finished wall volume:
wallVol = L × H × t
compactedSoilVol = wallVol × 1.30
soilMass = compactedSoilVol × 1800 kg/m³
stabilizerKg = soilMass × stabilizerPct / 100
labourDays = wallVol / 0.8The 0.8 m³ per worker per day rate assumes a small crew with a rented pneumatic or electric compactor. Hand tamping is roughly a third as fast.
Worked example
A perimeter wall 30 m × 2.7 m × 0.40 m with 8% cement stabilization:
- Wall volume = 30 × 2.7 × 0.40 = 32.4 m³
- Loose soil = 32.4 × 1.30 ≈ 42.12 m³
- Soil mass = 42.12 × 1,800 ≈ 75,816 kg
- Stabilizer (8%) ≈ 6,065 kg
- Labour-days = 32.4 / 0.8 ≈ 40.5 days (single worker, with a compactor)
Sources
- CRATerre rammed-earth practice (compaction factor, density, stabilizer percentages)
FAQ
What is rammed earth and how does it differ from cob or adobe?
Rammed earth is a damp mix of subsoil compressed in temporary formwork until it sets to a dense, stone-like mass. Unlike cob (hand-shaped) or adobe (cast and dried first), rammed earth is built up in 100 to 200 mm thick lifts, each tamped or vibrated to maximum density before the next lift goes on. The walls have crisp, vertical surfaces and visible horizontal lift lines.
Why multiply the wall volume by 1.30 for subsoil?
Loose subsoil bulks 25 to 35 percent above its compacted volume. The calculator uses a 30 percent factor — 1.30 × wall volume — so that the order quantity for loose soil delivered to site matches the finished compacted wall volume after ramming. Tighter or sandier soils may need a different factor; weigh a known sample if you want a precise figure.
How much stabilizer should I add?
Plain rammed earth needs 0% stabilizer if the soil has 5 to 25 percent clay and the wall is protected by good roof overhangs. Cement-stabilized rammed earth (CSRE) typically uses 5 to 10 percent cement by mass to make the wall water-resistant and faster-curing. Lime stabilization is gentler and uses 6 to 10 percent. The default of 8 percent is a sensible middle ground.
Why is soil density assumed to be 1800 kg/m³?
1800 kg/m³ is a typical figure for compacted earth — slightly less dense than concrete (~2400) but well above loose subsoil (~1400). Real density varies with mineralogy and compaction effort. If you have a Proctor test result for your soil, plug that in; otherwise 1800 is a defensible national-level estimate.
Why does the labour estimate use 0.8 m³ per worker per day?
0.8 m³ per worker per day is a reasonable productivity figure for a small crew using a rented pneumatic or electric compactor. Hand tamping with timber rammers is far slower (around 0.3 m³ per worker per day). Larger formwork systems and motorised compactors raise productivity to 1.5 to 2.0 m³ per worker per day. Adjust based on the equipment available locally.
Is rammed earth safe in seismic areas?
Plain rammed earth is brittle and performs poorly in earthquakes. Stabilized rammed earth with internal vertical reinforcement (steel rebar at corners and openings, plus a continuous ring beam) can be used in moderate seismic zones, but always have the design reviewed by a structural engineer. In high-seismic zones (parts of Nepal, Kashmir, north-east India), prefer reinforced cement-stabilized rammed earth or a different system entirely.