Damp on gable end wall - condensation..? What solution

[chalkstorm]

Hi all Been a while since I've posted - only seem to come back these days for advice.. so please be gentle! I've got an old house - built in 1880 - and while decorating (he is downstairs as I type), we have found damp patches on a gable end wall

- at low level in the living room. It seems to match areas where furniture has been up close - although there is also some around a chimney breast - and some in the corner of the room (no furniture there). We've dug into the plaster with chisels and it doesn't seem damp inside - which is odd.

The room doesn't get much use - has had new double glazing and one of these plastic coating renders applied in the last 12 months. The decorator thinks it isn't rising damp (the concrete floors are dry - and the skirting is fine) - but I'm not sure.

I've got rentokil and

in this week to have a look.

Any thoughts...?

Thanks in advance

Simon

[Bob Mannix]

Thought #1: Rentokil are b***** expensive Thought #2: It's lack of ventilation and a cold wall. Move furniture out a bit and improve ventilation

[The Natural Philosopher]

Thats condensation for sure..

- although there is also some around a

Mmm. Must be condensation there also if the plaaster is drier below the surface.

Insulate the wall and leave the trickle vents open.

[John Rumm]

Given the age of the place, the walls will be solid and hence colder to the touch. The application of an impermeable coating on the outside will also prevent one of the ways that walls of this type get rid of moisture

- i.e. evaporation. The proximity of furniture etc will reduce air flow and convection on the inner wall surface. Installing DG will also remove any natural ventilation from draughts. These all add up to a classic scenario for condensation to form on the wall. Its also a vicious circle in that as the wall gets wetter it will also conduct heat better, and hence attract more condensation.

The danger is that given time the wall can get saturated and the you get the risk of wood rot on the back of skirtings, floors etc.

The immediate solutions are adequate heating and ventilation. You need to minimise water production in the area as well - so ventilating cooking or washing steam produced near it before it can be a problem. Not drying clothes over radiators etc.

Another thing to check in many cases (but I suspect does not apply in yours, since it sounds like you have solid floors), is that there is adequate airflow under the floor from air bricks etc. This allows the wall to shed more moisture.

A more lasting solution is to look at ways of insulating the wall so that you can more easily maintain the inner surface temperature above the dew point. Your options here are limited to dry lining inside, or possibly external solid wall insulation.

Chances are they will stick a timber "damp meter" on the wall and tell you its wet, then suggest all sorts of drastic and pointless remedies!

[chalkstorm]

Thanks all - think you've confirmed what the decorator said really...

I've run a dehumidifier in there for months - and it fills, I empty it... it fills... and so on.

It rarely gets heated - and rarely used. Better half always wanted the doors closed at night and when we are at work (fire/smoke etc) - but that'll change. Will also leave the windows on the vent position, locked of course.

I like the Shriver system - sounds like it will do the job (after some research) - and don't really want the upheaval of dry lining or insulating the walls - but I suppose this is the time to do it (just means the decorator has to stop what he is doing...) - unless there is an easy way of doing it... (I'm cr4p at DIY hence my pathetic questions on here!)

Thanks again

[Clot]

I wholy agree with these comments.

If the room is rarely used, presumably it also is not as warm as the rest of the ground floor? What is the proximity of the room to the kitchen?

I would be inclined to install a dehumidifier and use this from time to time during the winter months.

[Clot]

I posted before downloading this last post.

Seems like you are on the right track.

Good luck.

[Jim]

Is the chimney still in use? Sometimes people seal off fireplaces without providing a proper vent, meaning that damp will build up over a period of years in the chimney and leach into the surrounding brickwork.

It can take months and months to dry out even with the root cause fixed.

[Stuart Noble]

At this time of year I'd be looking outside for rain penetration rather than condensation. IIRC the OP has an acrylic coating on the exterior wall? Good stuff if it's applied well and properly bonded to the brickwork, worse than useless otherwise

[Rad]

Dear Simon You would be well advised to ask yourself some searching questions before spending money on either Rentokil or Schrijver First Schrijver

How long has that particular legal entity been in buisiness? Have any of the directors or staff any connections with Dutch companies offering a similar service with a similar product that went bust in the last 40 years not once but twice under different names? Is is possible to cure rising damp by only doing external walls? In this context what is the logic of not doing internal walls which are equally founded on soil just as are the external ones!? Is plastering recommended and if not what reason given that if there is hygroscopic material present that is the only sensible solution? Do you trust any company that offers a life time guarantee? or indeed natural products? or indeed states "Research shows.." with no references. Are they members of the PCA/BWPDA? Does the surveyor have the CSRT?

I could go on at length but by now you will either get the message or bury your head firmly in the sand and go your own way

Rentokil Expensive but will pass all the above questions.

What is the problem?

It is either hygroscopic salts in the chimney breast caused by burning coal over the last century or condensation or lateral penetration. You have elimnated the latter with exposing dry brick so it is one of the other two

Is there any black mould? If so that is condensation Is it by the furntiure? if so others have correctly told you what to do

I suggest you map the damp and spend your money on a damp meter not a survey and assess if it is coming and going with the weather - if so it is hygroscopic if not and black mould, it is damp

I will let you know what to do when it is identified! Chris

[NT]

oh dear

The simplest option is to use the dehumidifier more. Just alter its setting. Dehumidifiers have made many once troublesome damp problems easy to resolve. A conventional 'proper' repair would involve ventilating the room more, probably heating it more, and maybe insulating the wall. Dont assume its non-cavity, there are a fair number of cavity walls from the 1800s about, and CWI is very cost effective.

NT