damp meter readings

[opps]

I recently purchased a digital Draper damp meter from toolstation.

My previous analogue meter used a green, amber and red scale. The new meter just displays a percentage.

I appreciate that I am only measuring conductivity but what would be considered normal?

My client has a water stain on an exterior brick/plaster wall that was caused by a leaky roof. The roof has been repaired but I was hoping that the damp meter will tell me if the leak has been fixed or not. At the point of the stain I get a reading of 0.7%. Readings 1m to the left and right of the stain drop down to 0.5.

is 0.7 ok?

 

[^woody^]

0.7 of what? It's meaningless.

Leave the meter in the box, and if there is a stain after rain then the leak has not been fixed.

An area of previously damp plaster always gives elevated moisture readings.

 

[opps]

0.7%, sorry forgot to add the % sign.

thanks for the heads up about elevated moisture.

I used the meter because stains often bleed through matt emulsion. I don't want to use stain blocker only to discover that I am hiding a problem

Cheers

 

[^woody^]

0.7% (less that one percent) won't even be a realistic figure.

The point is, it's meaningless whatever it is.

Damp meters are calibrated for timber. They can be used on other materials, but then scale is wrong, so the user needs to know how to interpret the readings relative to the rest of the walls and ceiling. The meter can't just be placed on the wall and a reading taken as that had no context at all.

You are wasting your time trying to determine if that roof is still leaking by using a damp meter. If it's leaking, you'll see it.

If you just put the meter on that patch it will invariably show a higher reading than elsewhere on the wall. But that might be normal.

So unless you are experienced in making the interpretation, just looking at it is the best thing to do, and you won't go wrong.