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Rising damp and the defective DPC assumption

January 27, 2012

Damp party wall claimed by a remedial contractor as rising damp

I was recently involved in a damp investigation, where prior to my arrival a remedial contractor had inspected the property and reported that the party wall was suffering from rising damp. The homeowner was suspicious and invited me in to take a look.

To cut a long story short the actual cause of the damp wall was a pipe leak below the timber ground floor and not rising damp at all. (Rising damp being moisture rising up a porous wall, containing nitrate and chloride salts and which originates from the ground).

Anyway, the reason for troubling you with this tale is because what happened next is important and therefore you need to be forewarned. See also the piece I wrote on rising damp in 2011, entitled 2 awkward rising damp questions.

When I confirmed to the homeowner that the cause of the damp wall was a leaking pipe, the homeowner contacted the remedial contractor who diagnosed the rising damp and complained.

The remedial contractor stated that their rising damp diagnosis was based on an assumption that the damp wall was caused by a defective damp proof course (DPC) and not from any other building defect.

To conclude, it would seem that rising damp is being diagnosed by some remedial contractors as a default position in an attempt to secure the lucrative damp proofing work. However, the diagnoses may not actual be a definitive diagnosis at all, but a speculative diagnosis based on an assumption. This “defective DPC assumption” has to be used because the contractor didn’t thoroughly investigate the dampness defect and obviously had no intention in doing so!

  1. Melanie permalink


    I have found your articles on damp very informative. We have recently had a diagnosis of rising damp on an exterior wall. I am dubious as to whether the damp is really rising damp by the strict definition (i.e. water moving from the ground by capiliary action) as my husband and I believe we have identified the source of the moisture and dealt with it (prior to the surveyors visit). However, it is quite obvious even to an untrained eye that our existing (very old) DPC is defective. We have had a specialist damp surveyor in who have quoted for remedial works including a new DPC and plaster with a water and salt resistant additive included. In this case would you recommend replacing the DPC or as we have dealt with the source of moisture (expanding foam filler that had filled an air brick that was at ground level, next to a path that angled towards the house, the foam was soaking wet, has since been removed and we are putting in a drainage channel that feeds into the storm drain alongside the house) can this work wait?

    Any advice would be appreciated.

    • The reason why the damp surveyors recommended a new DPC is to merely give you what all home owners want, a dry unblemished wall at a price. However, I am interested in ensuring the source of the dampness has been identified and removed first. I would wait until you are sure that the wall is starting to dry out…which it will if you have removed the source of dampness. You home was not designed and built to be damp so something has changed which has now made it damp.

      Rising damp is a bit of a wheeze because moisture does rise up a porous brick wall. However, I’m not at all interested in the damp pathway (the wall) I’m interesting in establishing where the dampness is coming from (the damp source). Its usually Gutters, Gulleys or high Ground levels. The 3 Gs.

      It sounds like you have been reading lots of my blogs!! Well done. Giving you the information to self-diagnose dampness is my mission in life.


  2. Melanie permalink

    Thanks for your comments. The wall is definitely drying out. We discovered the problem about two weeks before Christmas when our toddler pulled the bookcase down. At that point the wall was so wet water droplets were left on your hand after touching the wall. Our main concern is what to do next. Our toddler has a mould allergy and the mould spores have been making her ill (diagnosed around the same time we found the damp) so we want to make the house safe for her, but allergy proofing our home has led to a lot of unexpected costs so we want to differentiate between ‘need to do’ and ‘nice to do’. I saw a documentary a few years ago that talked about the myth of rising damp, that coupled with the fact the wall was fine 2 years ago when we moved in made me suspicious. I only found your blog this afternoon, but it reiterated a number of things I’d been thinking already.

    • I started publishing the posts about dampness because of the unbelievable amount of nonsense and miss-information being talked amount dampness. To solve a dampness defect you have to trace the symptom back to the source. The fact that some people give the dampness a direct (e.g rising) is not very interesting to me. The dampness must be coming from somewhere so it seems logical to me to track it back to the source. Once the source has been established you can then start developing a strategy to eliminate it forever!!

      It isn’t always possible to prevent it but improvements are always possible. Condensation is sometimes very difficult to resolve because of the size and type of the property.

      I hope this helps.

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