How much does damp proofing cost?

It’s easy to jump to the worst possible conclusion when spotting, say, tell-tale bubbles and/or peeling wallpaper, or perhaps a dank and ugly patch of mould: that your property is as damp as a ducks’ nest, that the situation is catastrophic and that remedying the problem will come at the expense of that trip of a lifetime you’ve been hankering after.

The good news, though, is that it’s rare indeed that damp is as bad as it initially seems. Of course, the wallpaper will have to be stripped and the wall most likely re-plastered. But in most cases, the masonry itself will be retrievable. It simply needs to dry out.

Three main factors are responsible for damp: condensation, rainwater and rising damp, and it’s the latter phenomenon that we’re concerned with here.

So what is it? Rising damp is the common term used for the upward movement of groundwater in the lower sections of walls by a process called capillary action. It’s characterised by a “tide mark” on affected walls, caused by salts contained in the groundwater.

When the water evaporates, the salts crystallise and can cause plaster to deteriorate. And with water continually wending its way up, the situation will perpetuate. (A side-effect of rising damp, incidentally, is that a damp wall will lose more heat.)

So how to tackle the problem? It’s most likely the case that the property already has damp proofing older houses use, for example, a layer of slate between the brickwork, while well-built modern houses include damp proofing in the form of a synthetic damp-proof course (DPC), about 15 cm above ground level, to act as a barrier through which water – in theory – cannot pass.

However, the damp-proof course can be broken or incomplete, allowing moisture to find a way in – or rather up: ‘bridging’ as it is known.

Poor drainage can also be a factor, so it’s certainly worth checking for standing water in crawlspaces and/or the basement. Another factor, meanwhile, might be any raising of the ground level next to an external wall. If air bricks are now blocked, or ground level stands above the original damp-proof course, then moisture can find a way up.

It stands to reason that the more damp-proof course there is, the less chance there is of rising damp developing. But just a few millimetres of ‘bridging’ is sufficient to cause it.

And how is rising damp treated? That depends on its severity and each case is unique. Examples of the treatments Danford Brewer & Ives offer are:

  • Removing the surrounding soil or bridging material to be a minimum of 150mm below the existing damp-proof course
  • Injecting a chemical damp-proof course
  • Replacing any damp or rotten flooring
  • Removing and replacing any plaster work, skirting boards, radiators etc. if necessary

One important thing to stress, though, is the competence and experience of the person(s) investigating the problem: misdiagnosis can happen – and since the wrong form of treatment could then be prescribed, the overall cost will eventually be higher.

An example: we mentioned earlier how salts form causing plaster and wallpaper to peel. This might be a feature of rising damp but other phenomena (such as heat from a fire) can also cause salts in masonry to crystallise – resulting, perhaps, in damp-proof course work that is completely unnecessary.

And the cost? A good rough guide is £60 per linear metre +vat. Therefore, an average-sized living room of 4 metres by 4 metres would cost around £270 + vat per wall. But, as mentioned, each case is unique. What we can say with a measure of confidence, though, is that most jobs will take us a couple of days.

If you have any queries – whether it’s about damp proofing or any of the other building services Danford Brewer & Ives offers, such as timber treatment, basement conversions, extensions or building maintenance – then please contact us. As ever, we’d be delighted to hear from you.