DIY Doctor

damp problem over the chemical damp coure membrane

Postby aness » Mon Aug 31, 2009 5:26 pm

can anyone help?
i have had 3 reputable companies to assess and quote for 2 remedial damp works within my property - they all have a different take on the problem and vary in their solutions ( and price 600-1000£ ex vat.) not surprisingly i am very sceptic and reluctant to do anything!

i have lived in the 2 bedded terraced victorian house for about 6 years.
last winter a large damp patch appeared in the front room above the radiator- there is a damp proof course in place.

i have been told that a) the damp course has been compromised and the plaster needs to be ripped off and another damp course injection carried out. equally i have been told that the damp proof course in in tact and the most likely cause is that the damp has been trapped above the chemical damp course membrane and is simply "coming out" ,recommending that the plaster is hacked off and then replastered.

another damp patch (large) appeared over the kitchen wall unit cupboards- there is an extrnal w.c , the roof joins below the damp level -
i have been advised we dont know why this is happening to it must be penetrating but we dont know where!

does anyone have any sugestions
Rank: Labourer
Progress to next rank:
Posts: 2
Joined: Mon Aug 31, 2009 5:08 pm


Simply Build It

Postby finch » Thu Sep 17, 2009 4:08 pm

OK, number one - chemical damp proof course is worse than useless as it will only disguise the damp, not cure it. It is a bit of a scam.

If the damp is appearing above the radiator it is unlikely that your damp proof course has been compromised as the damp is too high up. Is your radiator under a window? Is water getting in around that?

A common cause of damp above a metre or so is broken guttering - the water is getting down inside your rendering and making its way through.

It's no good getting someone to replace the plaster until you've got to the root cause of the problem. But if I were you I'd start looking upwards for the problem, not downwards!
Rank: Labourer
Progress to next rank:
Posts: 1
Joined: Thu Sep 17, 2009 4:03 pm

Postby aness » Sat Sep 19, 2009 3:33 pm

thanks for that - i am glad it was not just me being paranoid!

i am holding fire on any "remedial" works as i completely agree that
the cause of the problem must be identified reliably before money is thrown
at it!

no the rad is to the right of the window
i will check the pointing - the property isnt rendered-
as you indicate penetrating damp appear more likely given the height that this damp patch (measuring approx 2'x2') lies

i am going for a fourth opinion next friday !
Rank: Labourer
Progress to next rank:
Posts: 2
Joined: Mon Aug 31, 2009 5:08 pm

Postby Perry525 » Tue Sep 22, 2009 1:04 pm

August was pretty damp, it rained here 19 days in August. The last 15 of September have been dry.
There is every likelihood that your problem is down to wind driven rain.
Does the wall in question face the prevailing wind?
If its exposed, the rain could be hitting the wall with the force of a bullet and the wind may be blowing the rain through the mortar.
That is why cavity walls are required these days.
The solution may be as simple as a visit to your local box store and the purchase of some silicone paint to cause the wall to shed the rain rather than it soaking in.
Rank: Site Agent
Progress to next rank:
Posts: 734
Joined: Fri Jul 06, 2007 7:35 pm

Display posts from previous
Sort by
Order by

  • DIY How to Project Guides
  • DIY how to tutorial projects and guides - Did you know we have a DIY Projects section? Well, if no, then we certainly do! Within this area of our site have literally hundreds of how-to guides and tutorials that cover a huge range of home improvement tasks. Each page also comes with pictures and a video to make completing those jobs even easier!

  • Related Topics