What is Gravimetric Testing and why should I have it?
Gravimetric testing for damp is a method used to measure how much moisture is actually inside a building material (like plaster, brick, concrete, or timber) by weighing a sample before and after drying it.
It’s considered one of the most accurate ways to assess damp because it measures the real moisture content rather than relying on surface electrical readings.
How it works
- A small sample of material is taken from the wall, floor, or other affected area.
- The sample is weighed immediately (“wet weight”).
- It is then dried in a laboratory oven until all moisture has evaporated.
- The dry sample is weighed again (“dry weight”).
- The difference between the two weights shows how much water was present.
The moisture content is usually expressed as a percentage:
Why it’s used
Gravimetric testing helps distinguish between:
- genuine damp problems,
- condensation,
- residual construction moisture,
- salts contamination,
- or false positives from electronic damp meters.
It is commonly used in:
- building surveys,
- damp investigations,
- insurance disputes,
- heritage buildings,
- and legal/expert witness reports.
Advantages
- Very accurate
- Measures actual moisture content
- Less affected by salts than electronic meters
- Useful for confirming rising damp claims
In the UK, gravimetric testing is often referenced in investigations relating to “rising damp”
because many surveyors consider handheld conductivity meters alone insufficient evidence.
