Damp and Timber FAQs

How can I have rising damp on an internal wall?

The answer is simple. Any wall that is structural i.e. has a foundation is susceptible to rising damp.

How high does dampness rise?

There is no definitive answer to this question. It depends on many factors such as the thickness of the wall, the local water table, the internal temperatures, the type of material used to construct the wall etc. The common belief is that dampness will only rise up to 1m. This is not the case. We have commonly seen rising damp to greater heights. Most remedial contractors routinely specify removing the plaster to 1m high. The big risk is that the inspection has not been carried out with due care and the heights of the dampness not been recorded then the plaster is not taken of high enough. The client is left with what is known as ”salt bands”. Pockets of hygroscopic salts above the line of the new plaster. The bands will become increasingly wet when the humidity in the property rises and will never dry out. At Marsden Damp Services Ltd we see this problem virtually every day of the week on work carried out by other companies. The solution-Remove the affected plaster and apply a specialist render (by this stage the property has usually been decorated and it involves major disruption and cost).

Who do I trust to give the right advice?

The nationally recognised qualification for a remedial surveyor is the C.S.R.T –Certified Surveyor in Remedial Treatments. The exam is the benchmark in the industry. The vast majority of so called expert surveyors have no formal qualifications. To use an unqualified surveyor to look at your property to put it bluntly it is the equivalent of having a mechanic with no formal training or qualification M.O.T your car. The big difference is that your property is the biggest single investment you will ever make. It never ceases to amaze me that people take advice from someone with no professional qualifications when looking to purchase or maintain that very expensive investment.

What information does a moisture meter provide?

The electronic moisture meter used in the right hands can be a very useful tool. In the wrong hands it can be a very misleading tool. Basically all the meter tells us is that moisture is present in the area being tested. It does not tell us the cause of dampness. The cause can only be established using experience and a visual inspection. It should never be assumed that it is automatically rising damp. More often than not it is not rising damp but another source of moisture such as rainwater ingress, condensation, leaking plumbing, bridging wall plaster etc. The meter will only give accurate moisture percentages on timber and depending on the type of meter used concrete screeds. In conclusion the meter is a tool that is used to assist the surveyor in coming to an informed decision as to the cause of dampness.

I have never had a condensation problem before, so why now?

There are many reasons why condensation suddenly occurs. It is usually due to a change within the property either in the number of occupants or material changes such as double glazing being fitted etc. The problem is that we live in insulated boxes. Over recent years we have seen more use of double glazing, increased insulation within the property, UPVC doors, increased draught exclusion etc. At the same time we have seen the reduction of open fires. We shower more than we ever have in the past; most homes have a tumble dryer, washing machine. In a nutshell we have sealed our property and are producing huge amounts of moisture laden air within it = CONDENSATION. Believe it or not one of the most common causes of condensation is babies and teenagers. If you have a baby in the house the washing machine will never be of and in addition the steriliser will be getting plenty of use. Teenagers are notorious for having long (very long) showers. In a recent case (ive seen hundreds like it) a client contacted Marsden Damp Services Ltd to investigate a serious condensation problem. She had lived in the house for 8 years with no problem previously. I asked what had changed in the recent months. She said nothing. I asked if there were any new additions to the family. The answer was that her 18 year old son had returned home after a 5 year period living with his father. I asked how often he showered and for how long. The answer- twice a day and for anywhere between 30 and 45 minutes. Problem identified!!!!

Can condensation be controlled?

The simple answer yes. There are many ways of dealing with the problem ranging from de-humidifiers, to air bricks (used in the right areas and of the right type), heat recovery units, positive air systems, extractor fans but to name a few. It is essential that the problem be identified and the right method of control is provided. This can only be done after a thorough investigation by a competent surveyor. Many people write of condensation as a minor issue. It can often be far more damaging to your health and wallet than rising damp.

Can we install a damp proof course without removing the wall plaster?

The honest answer is no. There is a slight chance that the wall will dry out and the plaster will be ok. The odds are stacked against this happening. I have literally seen thousands on cases where the client has been advised that the plaster can be left intact. 12 months after the DPC has been installed the wall is still showing damp. The client goes back to the original installer and they are told that the walls need to be re plastered. By this time the house has been decorated, carpets laid, and furniture in place. Every client’s nightmare. The hard facts are that there is no way of getting past the removal of the wall plaster. When a wall is affected by rising dampness the ground water brings with it mineral salts. These salts are Hygroscopic (they absorb moisture from the atmosphere). Over a period of time they build up on the plaster surface and the wall plaster acts like a sponge absorbing water from moisture laden air. The wall plaster must be regarded as part of the DPC system. The specialist plaster and the DPC combine to provide an active barrier to control rising damp.  If there is no need to remove the plaster then I would suggest that the wall was not suffering from rising damp in the first place!!!! That is where the expert diagnoses is essential.