The buyers’ surveyor will probably come armed with a moisture meter. He will put it into the wall and may report that he has detected rising damp. When someone reads about rising damp, they assume the house is virtually fit for demolition. The buyers will be advised by the surveyor to get a specialist damp treatment company to do a survey.
The reason for this is that it takes the risk off the surveyor’s shoulders and put it onto someone else. The damp treatment company is, of course, naturally disposed to confirm the prediction that rivers of water are forcing their way up your unprotected walls, and they will offer to put it right at the cost of several thousand pounds.
With the prospect of your sale falling through, you will be under considerable pressure to agree to knock something off the price for the cost of the works and the inconvenience to the buyers of having plaster hacked off the walls of their living room up to waist height for up to six months.
But quite a lot of the time, the diagnosis of rising damp is absolutely wrong. In fact, one London borough decided to stop accepting rising damp as the cause of dampness in their many hundreds of buildings and instead to look for other causes, and they invariably solved the dampness problem by some simple building work or repairs.
If you think about it, moisture rising from the ground is unlikely to be a widespread problem. Damp proof courses have traditionally been made of bits of slate inserted between bricks a few inches above ground level. Let’s face it, if there really were underground geysers of water trying to force their way up walls, they would easily bypass some bits of slate with spaces in between. The reality is that there is obviously moisture in the ground, but it is kept at bay by relatively simple procedures such as those.
You may have problems from moisture rising from the ground if the earth or concrete outside the house is banked up over the damp proof course. For example, if you bank up a flower bed against the wall, or if you lay down a concrete parking area. But that is positively inviting trouble and it is very easily put right by moving the earth or cutting back the concrete from the surface of the house, after which the minimal barrier will work again.
So, getting back to the surveyor and his damp meter, there are a couple of questions you need to ask the surveyor. If he has detected moisture, has he checked what material it is in? The meter actually doesn’t measure dampness, it measures electrical resistance. This can be caused by water; but perfectly dry breeze-blocks can give the same reading.
A second question would be: Why has he concluded rising damp, rather than investigating condensation, bad pointing of the brickwork, or a leaking pipe?
It is true that damp proof treatment may produce a dry reading after it is done, seemingly proving the surveyor right. But damp treatment involves injecting chemicals into the wall which prevent moisture moving through it, and then re-plastering the surface of the interior with water resistant plaster. So, even if the real problem is a broken pipe inside the wall which is leaking slightly, that will just continue to do damage invisibly behind the scenes.
It is important to appreciate that there is nothing intrinsically wrong with a bit of dampness. Of course, the plaster of your internal walls needs to be dry to the touch. So, do outside walls most of the time. But dampness is always going to be present in a building’s structure, and it is a good thing. Buildings are meant to ‘breathe’. They get wet when it rains, and the rain evaporates.
Remove dampness altogether, as happened in some particularly dry hot summers in the 1980s, and you end up with an epidemic of cracked walls and subsidence problems. The crucial distinction is that you don’t want moisture in your living space. You can point out to your buyers that you have been living perfectly happily in the property without noticing or being disturbed by the so-called dampness, and that detecting it somewhere in the depths of a wall is unimportant.
What needs to be avoided is a constant source of moisture which overpowers the balance of rain and evaporation. For example, a broken pipe which means that water is constantly dripping down the face of the wall will ultimately lead to dampness penetrating into the house. But that can be put right by some simple building work. Before you put the property on the market you should look round the property and spot broken or leaking pipes or gutters. The giveaway signs are fairly obvious – marks of wetness, stains, or plant growth on the outside of the building, and damp smells inside.
Obviously, moisture running down internal walls or pooling on window sills is a problem. (You don’t need a surveyor to tell you that.) The major cause of dampness is condensation. There are a lot of potential causes of condensation, all of which can be dealt with by fairly minor building works or changes in living patterns.
Specific areas of internal dampness probably indicate a specific building problem such as a cracked pipe behind the wall, but that also only requires minor building works to locate and put right.
But since the usual solution to damp problems is simple building works or changes in how you use the property, you would be best advised to think about this before you put the property on the market and so avoid the problem altogether because there is no doubt that a cry of ‘damp’ will put a chill in the heart of any buyer.