I am often asked by clients for an opinion on the ‘Dutch’ damp proofing system, which involves the insertion of ceramic tubes into external walls; and my answer is invariably the same: “I can believe young Peter's digit saved Holland from the deluge, but I simply cannot see how this system can work”.

The many houses I have visited that actually have it installed invariably reinforce this opinion.  I have never perceived it to make any difference to issues of dampness, except perhaps in a negative fashion. 

I remember quite vividly a 1960’s bungalow I visited in Shropshire a few years ago, where these devices had been installed on the northerly facing external wall of the bedroom. They had been added in an effort to reduce the effects of dampness at the base of that wall; a problem that had been diagnosed as ‘rising dampness’, even though there was a perfectly good dpc installed and no high ground levels or other problems that would jeopardise it.

In a beautifully straight line behind the bed position, and coinciding exactly with the position of the tubes in the external leaf of the cavity were a series of mould stains, which I concluded had occurred because the tubes were providing conduits for the cold northerly air, and had thus created cold spots on the internal face of the wall.

The original problem with this bedroom was that caused by condensation; but the salesman who persuaded the owner to buy his tubes had ignored this quite obvious fact. Let’s be kind and say he simply didn’t know.

In truth I have never felt the need to examine this system in depth: if people want to spend their money on it that’s their prerogative.  However, quite recently it was brought to my attention that an eminent and extremely well-respected colleague in the industry - one I would vouch for wholeheartedly - has taken an in-depth look at the subject and produced a report on it.  My understanding is that at this stage he doesn’t wish to publish but I have obtained permission to append it to my site.

My feelings are that under the most favourable of circumstances it improves very slightly on the natural phenomenon of evaporation; but its overall efficacy is simply not worth the money.

Have a read and decide for yourself.