What Is An Acceptable Damp Reading?
The short answer to this would be ‘up to 18-20 %MC’
If you are concerned about those handheld electronic moisture meters, here are a few points to consider before you ask the acceptable %MC values:
Based on the idea that moisture would increase the conductance of plaster, these devices only try to estimate the moisture on a surface. The problem is – improved conductance can be a result of many other factors.
These devices just are not equipped to even approximate the level of damp inside the walls or plaster. And the moisture on the surface can accumulate there for many a few reasons. The reason why it takes an expert to understand the true meaning of those numbers.
Their job is more to point us towards the damping source. So we can find the root cause of your issues and recommend the best solution available out there.
There is no common criteria or resistance that they use to estimate the moisture within the surface. It’s usual for differently manufactured devices to give different values.
The long answer would be that here isn’t such thing as an acceptable damp reading. Electronic damp meters are only best for finding the root of the cause of the damp.
However, as above, if you still want a number – 18-20 %MC moisture is usually considered normal for brickwork.