I've just discovered this wonderful website and hope someone here can help me. I stripped the wallpaper off in our living room a few weeks ago and discovered the 2 outside walls were damp. One of them has some dark mould quite low down, the rest just seemed damp as the wallpaper came off really easily.
I had a damp proof company round who took readings, said it was damp and recommended a dpc. I'm cynical so thought that they obviously would make that recommendation.
To be sure I had another company round who also said the same.
But while searching for info I found all the info about diagnosing the damp and I'm now wondering if a full dpc is necessary. There are big shrubs growing up the wall on both side of the outside of the house which I'll be removing. I can't really see any typical 'tide' marks of rising damp and I'm wondering if I could risk getting the room decorated with that polystyrene liner that insulates the wall, improving warmth and ventilation and removing the outside plants?
The house is 100 years old and has a slate dpc
Many thanks if you've made it this far and any advice gratefully received
Have you checked out the projects area: https://www.diydoctor.org.uk/projects.htm There are quite a few projects on damp (under D) that may be able to assist you, also the presenters of most of these projects Property Repair Systems are experts in this field.
You are totally right to be sceptical. Asking a 'specialist' company to offer an independent opinion means you will never get totaly independent advice. Their report probably starts something like " your request to survey and report on rising damp', thus concluding the problem before they have started. These companies ae all there to sell their DPC's.
In the first instance you have reported that the house has a slate DPC. DPC failure is extremely rare, although the so-called 'specialists' will have you beleve different. Your building has stood for 100 years without the need for a retrofit DPC and will probably last another 100 without the need too.
The second importnat comment you make is the presence of mould. Such mould cannot readily grow on dampness which is caused by ground rising moisture.
Your own investigations look to have drawn to the right conclusions. Without seeing hte problem or carrying out proper tests such as Hydrometer testing, salt analysis, calcium carbide testing etc, it sounds like the problem could be due to condensation.
The plants outside may also be causing a problem, also is the ground level high? it should ideally be lower than 150mm below the DPC level.
The background temperature of the walls needs to be raised and ventilation improved, this will help to reduce the affects of condensation but will not attend to the cause. In the kitchen and bathrooms, mechanical extraction should be provided.
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