Is Rising Damp a Myth, or Are We Asking The Wrong Question?
Updated: Jun 20
Rarely is such a difference of opinion faced among professionals than the question of whether ‘Rising Damp’ exists.
On one side is a whole industry of tradesmen that ‘fix’ the problem, but have been so active in doing so – often where not required – that they’ve provoked the other side, building surveyors, to rise up and denounce its actual existence.
The problem starts because there are very few actual cases of true rising damp to study, by far the majority of cases have alternate causes, water penetrating from elsewhere, high external ground levels or even salts in the plaster. Peel these other causes away and water rising in a wall by its own accord isn’t as common as you might think.
One of the main points of contention for professional building surveyors is the perceived misselling of damp proofing works, often injection treatment and re-plastering, inevitably costing thousands. If those selling these works purely consider the ‘cure’ without looking at the cause, then mistakes will happen. Unfortunately solving a damp issue holistically (looking at the whole building) isn’t in the interests of a damp treatment guy selling his services.
It's at this point then that you have to consider whether we are asking the right question. Should we be asking whether water rises in a wall, or more importantly, do the more recent innovations to prevent this - damp courses - fail? One of the very frequent diagnosis given by damp treatment firms for a perceived damp problem is that the ‘damp course has failed’. But do damp courses fail?
Damp courses became a required building component in 1875 with the introduction of The Public Health Act. Since then engineering bricks, slate, polyethylene and bituminous materials have been widely used very successfully to stop water at a low level and prevent issues above. These DPC’s when installed correctly at the correct height are totally effective and to our knowledge there is no known case of any of these materials ‘failing’ within the wall.
Not once in two decades as a contractor did I ever take down a brick wall and find that the slate DPC had crumbled to a useless powdery mess, or the bitumen had oozed completely out of the bed joint. That’s not to say that DPC’s buried in a wall with 25mm of mortar bridging the joint will be effective, installation is key, but that is also an issue often easily seen visibly. The fact of the matter is that the DPC’s don’t just fail as is commonly put forward and no one has yet come forward with evidence to the contrary.
So back to the question of rising damp, does it exist, is it just a myth created by the damp treatment industry? Personally, I sit somewhere in the middle of the argument & I believe the answers to the following questions shed some light.
Can water move within a wall? - Yes, the pathways that moisture can take in a masonry wall are well established, both as liquid and as a gas.
Can water ‘rise’ in a wall that doesn’t have a DPC? - Yes, damp issues on internal walls without external influences can testify to that, especially when you conduct a thorough moisture & salt profile and see the distribution of the salts at high level.
Will water rise past a properly fitted damp course though? - No, as long as the DPC is not being bridged (e.g by render or high ground levels) then there must be another source of moisture.
Is water rising from below the most common cause of ‘rising damp’? – No, condensation on uninsulated solid walls is by far the most common cause of damp issues that are often misdiagnosed as ‘rising damp’.
The point? Depending on what part of the country you live, the vast majority of housing will have been built post 1875 and should have fully functional DPC's and therefore be immune from true ‘rising damp’. In the vast majority of these cases, if there's a damp problem present then chances are it’s highly unlikely to be ‘rising damp’.
In our professional opinion, a homeowner with a damp issue would do well to investigate the source of the problem before they try to resolve it by chemical injection, damp proofing rods or internal render. Often this course of action can be more successful long term, be less disruptive and cost far less.
In reality, the broad basics for treating dampness is the same whether there is a DPC or not - ensure the base of the wall has good evaporation by lowering ground levels externally, provide good subfloor ventilation through use of air bricks, eliminate any penetrating damp sources such as leaking gutters & downpipes and importantly, control the environment within the house to avoid condensation. If these very basic measures are taken before we decide to inject or render a wall, then we could find we cure the problem outright, not just mask the symptoms.
So does rising damp exist? In this surveyors experience the answer would be yes, as a process, not as a cause of damp problems in itself. If you cure the real cause(s) the damp issue will inevitably be resolved.
If you need any advice over any damp issues that you may have then feel free to contact us.