Structural Moisture Content Calculator
Calculate the moisture content of structural materials (timber, concrete, masonry, soil) based on wet and dry mass measurements per ASTM D2216 / AS 1289.2.1.1.
Enter wet and dry mass values above to calculate moisture content.
Formula
Moisture Content (MC) is defined as the ratio of the mass of water to the oven-dry mass of the material, expressed as a percentage:
MC (%) = [ (Mwet − Mdry) / Mdry ] × 100
Where:
- Mwet = Mass of specimen in its natural/wet state (g)
- Mdry = Mass of specimen after oven-drying to constant mass (g) — typically at 105 ± 5 °C for soil/masonry, or 103 ± 2 °C for timber
- Mwet − Mdry = Mass of evaporable water (g)
Note: MC for timber is expressed on a dry-mass basis (as above). Some references use a wet-mass basis [MCwb = (Mwet − Mdry) / Mwet × 100], but the dry-mass basis is standard for structural engineering.
Assumptions & References
- Oven-dry mass is obtained by drying the specimen to constant mass (change < 0.1% over 1 h) at the appropriate temperature for the material.
- Timber drying temperature: 103 ± 2 °C (AS/NZS 1080.1, ASTM D4442).
- Soil/masonry drying temperature: 105 ± 5 °C (ASTM D2216, AS 1289.2.1.1).
- Timber structural dry service class: MC ≤ 19% (AS 1720.1, NDS). Above 19%, wet-service strength reduction factors apply.
- Fibre Saturation Point (FSP) for timber is approximately 25–30%; above FSP, mechanical properties are significantly reduced.
- Concrete acceptable MC typically ≤ 5% by mass for most applications; refer to project specification.
- Masonry acceptable MC typically ≤ 6% (AS 3700); higher values may indicate rising damp or water ingress.
- Soil MC limits are site- and application-specific; refer to geotechnical investigation report and compaction specifications.
- This calculator does not account for salt content, chemically bound water, or hygroscopic moisture — laboratory testing per relevant standards is required for compliance purposes.
- Standards: ASTM D2216, ASTM D4442, AS 1289.2.1.1, AS/NZS 1080.1, AS 1720.1, AS 3700, EN 13183-1.