Building Pathology: Conducting Damp Surveys

If your only tool is a hammer, every problem will look like a nail. This is very true when it comes to dampness inspections as the right tools and the right amount of knowledge and understanding is key to allowing maintenance staff to successfully determine the cause of dampness issues within properties. In this blog I will be putting across my view that staff within housing associations and local authorities, with the right training and equipment, can successfully complete good quality initial dampness inspections.

Dampness in buildings is one of the most common call outs from tenants that require a maintenance inspection. It can have a variety of negative effects on occupants and the building itself, some of the effects on the building can include:

  • Mould development
  • Decorative staining
  • Increased likelihood of fungal or insect attack to timber
  • Damage or disintegration to masonry walling
  • Loss of insulation quality
  • Physical damage (expansion or contraction movement)
  • Transportation of salts
  • Corrosion of fixings or supports

Maintenance professionals in social housing are the first port of contact when a tenant discovers dampness issues within their property. With the right tools at your disposal and a good understanding of building failures, most cases will be able to be resolved without the use of expensive specialists.

Ventilation specialists, building surveyors and dampness specialists can provide assistance for complex cases but in my view for the majority of cases the inspection can be completed by the social landlord / local authority maintenance staff.

There are various bits of kit out there that can assist maintenance staff in investigating dampness such as borendosopes, thermographic cameras, calcium carbide meters, data loggers and floor hygrometers. These items all serve their respective purposes but in most cases a moisture meter will be the most frequently used piece of kit.

The Protimeter MMS2

There are many dampness meters on the market with the Protimeter being one of the best for moisture analysis.  The MMS2 is an well rounded meter which employs a full range of building moisture diagnostics. It features the standard pin moisture measurement but also boasts many other impressive features such as:

  • Non-invasive moisture measurement
  • Hygrometer
  • Non-contact IR thermometer
  • Datalogging
  • Other attachments like deep wall probes and hammer pin instrument

These features will allow you to embark on a process of elimination in search for the likely causation for the dampness problem. For more information on the MMS2 please check out my full product review here.


How do they work?

Electrical resistance meters work by using the two pinned probes to measure the electrical current resistance. Wood has a high electrical resistance when dry but decreases when wet, so this allows the meter to detect this difference and display a moisture reading.

The non-invasive moisture measurement works by sending a specific radio frequency through the material being observed. Moisture is determined by measuring the change in the radio signal.

The IR thermometer works by determining the temperature via the infrared radiation emitted. The IR thermometer will have a detector called a thermopile which converts IR to heat, the heat is converted into electricity which is measured and the value is displayed on the device. You can learn more about IR in my blog post ‘Understanding Thermography‘.

Knowing the limitations of the equipment you use is important as well. Electrical moisture meters are calibrated for wood so it will give you a wood moisture equivalent reading (WME) for other building materials. This means in masonry you should use electrical moisture meters as ‘dry meters’ or an indicator of potential damp rather than a definitive reading. False high readings can be obtained from:

  • Carbonaceous material
  • Buried electrical cables
  • Foil backed wall paper
  • Salts

The reason why the wood moisture equivalent is needed is because different building materials can hold different amounts of moisture due to their density and porosity.  What is considered damp is generally as follows:

  • Timber 20 – 22%
  • Plaster above 1%
  • Mortar above 1%
  • Brick above 1%
  • solid floor above 80% RH

Why do the exact percentages of moisture in timber matter? Well sustaining moisture below 18% in timber will control the presence of the wood boring insects like the deathwatch beetle, low moisture content in timber can kill off larvae. The likes of dry rot needs a minimum moisture content of 18-20% in timbers to thrive and optimum growth occurs at 30-40%. So this means knowing this makes knowing the percentage of moisture quite important.

High levels of moisture in skirting and wall found during damp survey

Data loggers

Data loggers can be used on a long term basis for property monitoring or shorter term for condensation assessments. They allow you to gain a better understanding of the heating, ventilation and relative humidity in the property and allow you to give specific tenant advice based on the actual data procured. They are my secondary go-to piece of kit if the evidence is leaning towards condensation as being the source of the moisture problem.

Using data loggers in a property for around three weeks will allow you to build a picture of the internal conditions within the property. Air above 70% relative humidity is considered damp because that is the point in which mould growth can occur, so this is the threshold you are looking out for when analysing the data.

data logger results

I have used filesthrutheair USB data loggers for this purpose and I will be reviewing Protimeters BLE meters soon. It will be very interesting to see how these two loggers stack up against each other.

Cost Effective Solution

Training staff in house and procuring the right kit like the Protimeter MMS2 will have many benefits and will save your organisation in expensive dampness inspections or implementing unnecessary repairs. I would personally endorse the Scottish Lime Centre Trusts ‘Damp in Buildings Seminar’ presented by the one and only Mike Parrett as an excellent place to start if looking for good training. There is nothing in their calendar for this course but I am sure they will run it again next year as it was a very popular course.

Another good free resource is the likes of youtube videos, Bryan Hindle the managing director of Brick-Tie Preservation has an excellent video on the use of various damp instruments. He has also uploaded a number of other videos on various surveying topics, so I would encourage you to check that out.

I am a huge proponent of CPD and training and with maintenance staff’s existing extensive knowledge of their stock along with good dampness training they are more than equipped to carry out a great initial survey.

Investing in quality equipment will also increase the likelihood of a first time resolution which will foster more confidence from tenants and increase overall tenant satisfaction. Maintenance officers and property officers can effectively carry out dampness surveys if given the right training, equipment and support.

Assistance from specialists is sometimes necessary and knowing your own personal limitations is important but an over reliance on third party surveyors who may have an incentive to sell you a product is not the best way forward.

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