How do i check id damp wall is dry

baby-mechanic · 14 August 2008 at 9:47AM

Hi folks

We live in an Edwardian house, built with lovely thick walls.

Some of the exterior walls had rising damp, so we got it looked at, and were advised to get an injected DPC. Did this, and asked the company involved how long the wall would take to dry out. They said 2-3 years if we just left it to it's own devices, but a few months if we used a de-humidifier.

We've run a de-humidifier for a few months now, and would like to know how to check how the wall is drying out without getting someone in who'll probably charge for the privilage.

Thanks in advance for all thoughts and suggestions.

Powerful_Pierre · 14 August 2008 at 10:34AM

Running a dehumidifier has very little affect upon the drying rate of a wall. It removes air bourne water vapour only - it does not suck moisture out of the wall. Granted it increases the ability of the atmosphere in the room to absorb more water vapour but this is temperature dependant and the surface to volume ratios involved in a thick wall means this is virtually insignificant. Why are you waiting? If your wall has had rising damp it will be contaminated with hygroscopic salts which means even when the wall is 'dry' a certain amount of moisture will always be present due to the hygroscopic action of the salt contamination. It is for this reason that correctly formulated re-plastering should be applied on to walls treated for rising damp. If you have not re-plastered then nothing will change no matter how long you wait. Have the walls been re-plastered? If not were you advised thast they should be? The suggestion of a few months is massively optomistic and I would be concerned about the company's level of understanding.

Powerful_Pierre · 14 August 2008 at 11:50AM

The above meter will not tell you how much moisture is in a wall. It is just a very simple resistance meter, possibly calibrated for use on wood. It is just an aid to diagnosis but it does not provide quantitive figures nor does it differentiate between hygroscopic and capillary moisture content.

Edit: Previous post has been removed

How do i check id damp wall is dry

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