Soil testing manual
Understand your soil for different types of earth construction
The challenge
Lack of on-site testing methods
Between 2008 and 2009, Smart Shelter Foundation tested a vast number of soil samples in Kaski District of Nepal, to determine if the mountain soils were suitable for making stabilized earth blocks.
In rural and remote areas, such as the mountains of Nepal, lab testing equipment is generally not available. This highlights the need for simple field tests to rapidly screen soil samples and determine which earth-building techniques can be used for specific soil types and how they can be improved or modified.
Soil composition - an example
Earth construction has many advantages and is currently experiencing a major revival. Ideally, the soil can be sourced directly from the building site to reduce transportation costs. When building with earth, whether using cob, adobe, rammed earth, or stabilized blocks, it's essential to understand the basics of soil composition and its suitability for the chosen technique.
For example, in India, we built a school with cement-stabilized earth blocks (CSEB), which requires a ratio of 65-75% coarse particles to 25-35% fine particles. The ideal composition for CSEB is:
15% gravel (coarse particles)
50% sand (coarse particles)
15% silt (fines)
20% clay (fines)
Our soil tests in India revealed that our samples contained around 50% gravel and sand. Therefore, for each unit of soil, we had to mix in one unit of sand or quarry dust to achieve a mix with the ideal 75% coarse particles — the average of 1x50% + 1x100%.
Our research
While many soil testing manuals are available online, Smart Shelter Foundation has distilled this information into a single manual that is easy to use, complete, and correct. Our manual focuses on low-tech, on-site testing using simple tools and tricks, without the need for sophisticated lab technology. These field tests can be used for initial conclusions, which can be further examined with lab technology if it is available nearby.
