Dampness is caused by many factors and it is oft quoted that Surveyors mis-diagnose the causes of dampness. Personally I do not believe this but what I am convinced is true is that a home owners tend to either ignore damp and mould, a strange and self-defeating stance, or become paranoid and seek to completely eliminate all traces of moisture (which is not always a wise thing to do).
Nothing could be worse than ignoring the problems because they usually get worse. Our second reaction is often to get a specialist Damp Proofing contractor involved. Although this can be correct and proper it is my experience such salespersons often sell a solution that is not needed, and which costs you a small fortune. That solution usually means chemicals will be injected into the house walls and in this eco-world this cannot always be correct.
It is all subject to scale and degree but the wisest course of action is usually to get your local Chartered Surveyor in to inspect and advise you. I can be accused of profiteering here but I reject I am biased. Dampness can be caused by so many differing factors that a true analysis is absolutely essential to ensure the solution is sustainable. Where does damp occur, why and does a repair need to be completed?
The best way of preventing damp is to design an adequate barrier and to install it effectively during construction of the building. Otherwise a retrofitted system must be considered and such systems are often disruptive and costly.
Also one must consider a further serious problem in the industry of damp diagnosis – often the cause of the dampness problem is mis-diagnosed and this can lead to much unnecessary expense or, even worse, duplicated costs over a period of years as a second solution is then tried.
Condensation is often the actual problem and this can be associated with a lifestyle problem rather than a building defect: indeed, it is my experience that the large majority of dampness that as been rectified by chemical injection systems (see below) are, in fact, a combination of inadequate insulation and a lifestyle issue revolving around your own actions and methods of living in that particular building.
On top of these issues is the danger that historically the observed dampness may have brought with it minerals from the ground. These can migrate up and into wall-base plaster in your lower rooms. This contaminated plaster usually needs to be removed (but not always) and the affected rooms then replastered at high cost and disruption. The dampness may have also started the process of joinery or floor decay that may not manifest until many months later and so it usually pays to expose and lift floorboards before any works are specified – hense my assertion that it usually pays to get an experienced Home Surveyor to check out the home before works are started.
The Dampness Diagnosis Industry is one that is driven by a Free Surveys by the Company competing for retrofit remedial work. Often conflicts of interest result in misdiagnosis and all for the sake of home buyers or owners saving a few pounds by not calling for paid opinion from a local, independent Chartered Surveyor.
So, what are the main types of remedial system if an actual rising damp issue has been correctly diagnosed? Here is a basic list —
Chemical retrofit injection systems: these place chemicals within a wall such that the micro-porous structure of the masonry cannot take in moisture and this solidity prevents capillary attraction and so damp cannot rise into your home. Small holes are drilled into wall bases (usually outside but an interior system can be designed in some cases) and a chemical solution is then systematically injected into masonry until saturation point is reached.
Electro-osmosis: if a small electrical current (equivalent to that used by a doorbell) is passed through a wall it affects the rate of potential capillary attraction that causes water to rise in a wall (like a tree sucking water out the ground). This system typically has a Control Unit (an adaptive power source), Anodes drilled and set into the outside wall-bases plus, finally, an Earth Rod. These are provided externally and are effective if the circuit(s) is not broken or the power supply interrupted.
Physical = the introduction of a new barrier such as bitumen felt, plastic (polypropylene, EPDM or re-cycled), dense (engineering grade) brick course & mortar, lead or natural slate. Any physical barrier will need to be linked to any flooring membrane and be at least 150mm above outside ground levels. The precise position of the barrier must also ensure that embedded, suspended floor joists ends are protected from damp and resultant decay.
Schrijver System: (a proprietary brand product used as an example to identify any such system – a specialist physical system) = this relies upon inserted special devices placed inside a wall (inserted from the outside by a drilling process) that create cold spots to which water is drawn. That moisture is then collected and drained away safely.
Palliative measures – in essence these work on the principal that the damp is not the problem; instead you tackle and neutralise the effects of dampness rather than prevent the source(s) of damp (provided no serious consequence results from such proposals) — 1. Create a new inner skin with damp-membrane and insulant but with a vented space between damp old and stud new inner walls. Possibly complete this work in tandem with outside land drainage works. 2. Changes in occupants’ lifestyle patterns. 3. Provide better insulation and/or improve heating and venting of the building environment (or simply improve the control of such factors).
Arguments exist for each type of theory of repair, or action to combat dampness and its effects (mould, decay, health problems….). Factors to decide the best solution for you may include:—
• The robustness of the correct diagnosis of damp. This factor cannot be overplayed in importance as the large majority of dampness cases are initially mis-diagnosed by Surveyors.
• Whether the degree of damp warrants any actions at all.
• How green you require your repair solution to be.
• The effectiveness and longevity of the various types of solution.
• The costs, direct and indirect, of your preferred repair solution.
• Whether guarantees are issued, and upon what terms (such as being Insurance backed?).
• Whether it is wise to repair damp at all – eg: Cob walled buildings must be damp to remain structurally safe: eg: flint walls cannot be injected: eg: usually slim wall forms of Period Buildings need to breath and this precludes most remedial work methods.
• The peripherals such as the degree of Repair Company expertise required, whether Building Control Approval is need, length of time needed to complete the repairs, what conditions are placed on each repair method, any adverse effect on saleability or mortgageability of each type of repair system, etc……
• Sometimes remedial works might effect an adjoining structure and so the cooperation (sometimes mandatory under the Party Wall Act) of the adjoining property owner is needed before anything can be done.
In seems that the Industry has lapsed into saying the solution is a chemical injection remedial treatment, now what is the problem? Until we can get a little more sophisticated we will continue to complete unnecessary works and/or use chemicals when often we shouldn’t.
The crux of the matter often revolves around two factors (1) whether wall plaster needs to be removed and replaced as this greatly increases costs and length of contract, plus (2) are you prepared to accept that the way you live within the dwelling has caused the damp and mould and you may have to make lifestyle changes: (the latter scenario is real and it is my experience occupiers often will not believe the problem is self-inflicted. This plays into the hands of the rogue specialist damp companies).
It really is quite simple – as every home and method of occupation are so variable no one-solution-fits-all exists and therefore you need good quality advice. So, will you take advice from an impartial Chartered Surveyor or rely upon Bob the Builder or a company salesperson from a Dampness Contractor? The choice is yours.