Fact: this is incorrect.
The steady-height of rising damp depends on several parameters, one of them being the thickness of the wall fabric.
Facts and Figures
I recently came across a scientific publication in this regard, that analyzed rising damp in detail, providing some of the scientific formulas for the calculation of some of its most important parameters.
The figures were calculated for the UK, taking into account the average yearly evaporation rate for the UK, and the figures were striking. Here is an example for a 500 mm thick wall:
- The steady-state height: of rising damp: 1.12 metre
- Quantity of water stored per linear metre of wall section: 111 litres
- Water flow-through: 1.1 litres / linear metre / day. Or 408 litres / year / linear metre.
- Water travel time (residence time): 100 days to travel through the wall
I have re-created the formulas and calculations given by the research paper in an Excel file and calculated the above parameters for various wall thicknesses between 0.2 to 3.0 metres, covering:
- Normal residential buildings (0.2 to 0.5 m wall thickness)
- Listed buildings and churches (0.6 to 1.5 m wall thickness)
- Large conservation projects (2.0 to 3.0 m wall thickness)
Just for fun. please see the summary chart below:
As you can see from the above calculations, the thicker the wall the higher rising damp rises. This is normal, as a thick walls have much larger volume than thinner wall, so they can hold a lot more water than thinner walls. For residential buildings with thinner walls the average rise height of rising damp is indeed around 1m, however it can rise significantly higher for thicker walls.
Here are the numbers:
- 0.2 m wall thickness: 0.71 m rise
- 0.5 m: 1.12 m rise
- 1.0 m: 1.58 m rise
- 2.0 m: 2.24 m rise
- 3.0 m: 2.74 m rise
These calculations do not take into effect the hygroscopic (water absorbing) effect of ground salts, with which the rise height can increase even more.
A more in-depth discussion about this and other parameters of rising damp can be found here.
Several metre high rising damp occurrences are also mentioned in several scientific research papers - these usually can be found in thick wall monuments and churches.
Here are some examples:
Franzoni E.: Rising damp removal from historical masonries: A still open challenge - Construction and Building Materials 54:123-136, University of Bologna, 2014
Hoff, W.D.: Rising damp: Capillary rise dynamics in walls. Proceedings of the Royal Society. A Math. Phy. 463, 1871-1884, Aug 2007