Rising Damp Explained, everything you thought you knew, a little bit more and a few of my opinions!

People consider water a slippery substance after all, a wet floor can be slippery right? Well, In fact it’s not, water is an incredibly sticky substance.

Water molecules are made up of two hydrogen atoms and one oxygen atom which are covalently bonded to form the molecule H20. Due to the share of electrons water molecules are also polar meaning one side has a partial positive charge (the hydrogen side) and the other is partially negatively charged (the oxygen side).

Hydrogen atoms that are positively charged are therefore attracted to surrounding negatively charged oxygen atoms of other water molecules causing molecules to group together.

Think of this like the attracting forces of magnets where opposing polar forces attract 'Opposites Attract'. This bond between surrounding water molecules is hydrogen bonding and its cohesive forces have a lot to do with how water behaves. Together with ‘adhesion’ these are the forces that make water incredibly sticky.??

Because of hydrogen bonding, water molecules have a tendency to group and resist separation, and molecules on the surface of a liquid are attracted inwards to form bonds with other molecules inside the water mass. This is also the same phenomenon which causes water to form into droplets and what creates tension on the surface of the water 'Surface Tension'.?

Think about whenever you spill water or observe rain. The spillage is always retained in a pool and raindrops are always and circular. This is all down to hydrogen bonding because the cohesive forces between molecules pull them together. Surface tension is also what provides the ability of some insects to skate upon the water without sinking.?

Hydrogen bonds are approximately 10x weaker than chemical bonds however, it is possible to break a hydrogen bond by adding energy. When energy is added molecules excite causing them to move rapidly to the extent where eventually they will break free from surrounding molecules, thus sticky water becomes a gas - 'Evaporation'.

So, what does all this science have to do with rising damp??

Well, in addition to water molecules being cohesive to one and other, water molecules are also adhesive meaning they're sticky. Hydrophilic materials have pores which are basically columns of empty space, void tubes if you like. Within some building materials, these pores are created by driving out moisture from the material during curing/firing. The water which once occupied the space leaves behind an empty pore, a 'Capillary'. The problem is sticky water molecules attract themselves to the sides of these capillaries and if this attraction is stronger than the forces of gravity, water will want to climb – 'Capillary Action'.

Capillary action is basically the movement of a liquid across the surface of a solid caused by the adhesive attraction of the liquid molecules to the solid. Water molecules migrate through capillary pores due to the forces of adhesion, cohesion, and surface tension.

This climbing phenomenon occurs due to the unique concave meniscus curve which is created inside the capillary pore. As the water molecules are more attracted to the side of the capillary by adhesion than they are themselves, molecules in contact with the sides want to climb upwards. Cohesive forces between other water molecules mean that when one water molecule shifts position, it is quickly replaced by another in the chain, dragging the rest up with them.

It is the meniscus curve effect that is responsible for capillary action 'Rising Damp' and the smaller the pore the more pronounced the meniscus.

Pores, however, are not all equal they vary in length, continuity, and size all of which are characteristics that determine the porosity of materials and dictate the height of rise. Small thin pores will have a steeper meniscus curve and thus will create more?suction than larger diameter pores. As such, the height of water rise in pores with a smaller diameter will always be greater.

What determines the eventual height of rise is dependent upon a number of factors such as:

?1: The availability of water in the ground

2: The size of the capillary pores

3: Continuity between capillaries

4: The rate of evaporation

5: The forces of gravity.

6: The effects of hygroscopic mineral contamination.

?When these forces eventually balance out they are said to be in equilibrium.

Unfortunately, most organic building materials are not clean and will contain some degree of mineral contamination, groundwater does too. Because water is a solvent these minerals dissolve in solution. As water molecules climb the capillaries they also carry these dissolved minerals from the ground and within the masonry itself. These minerals are then transported through the wall in solution and deposited at the height of rise leaving behind a band of mineral contamination a - 'Salt Band'. These salts can be efflorescent meaning they'll crystalize as moisture evaporates and are noticeably visible as a light white powdery crystal on the surface. Some, however, are hygroscopic meaning they are seldom visible but remain within the masonry where their hygroscopic properties absorb moisture from the air contributing to the overall level of dampness.

So, there you go ! Now you should understand a little more about the mechanism of ''Rising Damp' and the forces which allow this phenomenon to occur.?

So now let’s discuss the fence, yes, the fence!?

The topic of 'rising damp' has a habit of dividing building professionals. There are those on the left of the fence who refuse to acknowledge it exists, we call them flat earthers. Those who believe the earth is flat, there are in fact nine planets and who probably spend their weekends playing war-hammer games on the floor in their pyjamas. It's no laughing matter, they walk amongst us!

Then there are those who sit on the fence, they acknowledge rising damp exists but insist it’s extremely rare, as rare as rocking horse poop I've heard quoted. I’ve read quotes from surveyors who boast of completing thousands of surveys in their career and having only ever found rising damp in 5% of cases! Really, my thoughts on that to follow.

Then there are those on the right of the fence who acknowledge rising damp is a thing and react appropriately when factual evidence-based diagnosis concludes so. I’m on that side, it exists and I don’t believe it’s as rare as rocking horse poop!

Now, consider this, there are approximately 25 million homes in the UK most of which will be constructed using porous building materials and many were likely constructed prior to the introduction of damp proof courses. Even those built with damp proof courses may also develop problems due to failure, breaches, constructional defects, and workmanship errors. I conducted a study a few years back to evaluate my most commonly encountered damp problems and assessed these in relation to the building's method of construction and era of the build. The results were surprising as most problematic properties I encountered were actually built with DPC’s that failed to function properly for a variety of reasons.

For those interested, you can read the article here: https://www.dhirubhai.net/pulse/industry-perception-study-russell-rafton-/

So, with 25 million UK homes, what do you think the chances of 'rising damp' being extremely rare really are? Less than 5% of all damp reported issues?.....

The trouble is, I find when I drill down into the opinions of those who sit on the fence that their findings are based on limited diagnostic experience (if any) and a predetermined mindset to align with a belief or the beliefs of others around them, so as not to look stupid, its almost a cult. It’s not unusual to consider they rarely find a case of rising damp when you discover they have very little or no experience in finding it! The next time you come across someone like this, just ask them how many times they’ve actually undertaken intrusive investigation or how much experience they have in quantitative moisture analysis.

Furthermore, too much diagnosis is undertaken using electronic moisture meters. Now we all know the pitfalls of electronic moisture meters and really these devices are best used to determine if a material is dry rather than wet, but they do have their uses. Believe it or not, however, they are extremely accurate when determining moisture profiles in masonry when compared to other quantitative techniques such as gravimetric analysis. ?

A number of years back I put this to the test, so I speak from experience and compared the results from an electronic moisture meter against quantitative analysis. The results may surprise you.

You can read the article here: https://www.dhirubhai.net/pulse/truth-moisture-meters-protimeter-russell-rafton-/

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The problem is in hands of the inexperienced, electronic moisture meters are a risky tool that can result in misdiagnosis. I published an article a while back titled “The Great Damp Illusion” where a client had been visited by a “damp wally” who diagnosed 'rising damp' based on instrumental readings from an electronic moisture meter. When I was instructed to follow the “damp wally” and provide my own diagnosis which was conducted by sampling for moisture and salt, my findings discovered the walls were in fact completely dry. The problem was to salt contamination and surface efflorescence.

You can read the article here:

https://www.dhirubhai.net/pulse/great-damp-illusion-part-2-russell-rafton-/

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So, the reality is if you have little understanding or experience in material science, damp diagnosis, or sampling buildings for moisture then it is to be expected that you’ll likely never find evidence of 'Rising Damp'.

Rising damp, it's a thing believe me I've years of experience diagnosing it but the cure for sure won’t be found by listening to the rubbish peddled by manufacturers of chemical products and in worthless guarantees, that we can agree on!”

Finally, if you've made it this far, I hope you found this article useful.

Thanks for taking the time to read it and if you have any questions or queries please don't hesitate to get in touch.

Happy surveying

Russ

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If you would like to learn more about damp diagnosis or surveying you may?also find the following articles useful:

A scientific experiment to demonstrate the recovery of flood damaged materials

https://www.dhirubhai.net/pulse/scientific-experiment-demonstrate-recovery-water-damaged-rafton-/

Independent damp surveyor vs Contractor damp surveyor, which is best?

https://www.dhirubhai.net/pulse/independent-damp-surveyor-vs-contractor-russell-rafton-/

Five things you should know before you book a damp survey or repair

https://www.dhirubhai.net/pulse/five-things-you-should-know-before-book-damp-survey-repair-rafton-/

Russell Rafton - Dryfix Preservation Ltd Senior Surveyor

Dryfix Yorkshires Leading Damp & Timber Specialists

A 6 x Industry Award Winning Company with the Property Care Association.