Rising Damp & Penetrating Damp-Vs-Condensation Dampness - The Difference Revealed.
During the many years and many properties we have looked at which have damp issue of some sort or other, certain things begin to stand out and become repetitive, so much so that it lead us to look more closely into dampness in homes in general. Now, before you go straight to thinking that I’m about to start on the tack of “there’s no such thing as rising damp” I will say that true cases of rising damp are nowhere as prevalent as you might imagine. experience shows that there needs to be some pretty specific sets of circumstances in place for rising dampness to occur. most of the time these circumstances are not in place. Often we get called to a property and the scenario is like this - the customer tells us the house has rising dampness and it can be clearly observed on the interior walls of the house. I’d like to point you towards a very useful video taken recently in a Georgian property, the interior walls presented with crumbling plaster, flaking paintwork and often a ‘damp smell’. in actual fact the property was suffering with a lack of ventilation which had manifest in a way which would lead one to thinking there was a problem with water travelling up the wall from the ground. In this case it stands t reason that that wall would have to be wet right the way through it. If it wasn’t then it can only be that the moisture is alighting on the wall from within the building itself. Take a look at this quick video below.
A short video illustrating the difference between rising damp and condensation damp.
Think of it like this; a cold pint of beer in a busy pub will very quickly gather much condensation on the outside of it. The pint of beer is effectively a thermal mass. That means it is an object with thermal mass in a humid environment - water vapour is drawn to it so that it can condense back to water (the stable state of water). I one were to cover a side of the glass with masking tape, pour the drink, watch the condensation form and then pull of the tape, as one would expect the portion which was covered in tape would momentarily be dry and free from condensation. Exactly the same scenario has happened to the wall in the film above and also in hundreds of homes around the country.
To take another example, take a look at the photo below.
This is the floor of a home recently visited by Dovedale Dampcure Services Ltd. Again, this is easily misdiagnosed as some king of rising or penetrating dampness. Certainly in this case that diagnosis could not have been further from the truth. Careful inspection revealed that the airbrick which were intended to supply the ventilation that this subfloor required, were completely bunged up with spiders web, detritus and wind blown debris and vegetation. They were simply not up to the job of providing decent subfloor ventilation. Add into the mix high humidity levels inside the property as a whole, and the whole thing was a ticking time bomb. the floor boards are supported by floor joists. The floor joist ends are supported and embedded in the walls. The walls are cold masonry with high thermal mass. The subfloor is soil and earth which breathes letting out much water vapor. The airbricks are blocked and can’t provide the ventilation the subfloor needs so the vapor finds the surface of the cold walls to condense back to a liquid on. The softwood joists are in direct contact with the walls and then get wet - repeatedly. before we even notice it the rot has already set in and the fate of the floor is sealed.
Another visual ‘tell’ is the very formation of dampness on the walls itself. please look at the pgoto below of a window on a cold morning. the glass has condensation on it and it forms in a very particular manner. it is in the shape of a gentle crescent. in the case of condensation dampness this shape is copied onto the walls, especially on nib walls, and also in corners on external walls.
These are some of the clues that we find in diagnosing exactly what kind of dampness we are dealing with when we arrive at a customers property.
