Walk-in shower high moisture level in exterior wall

[JAXJOE]

I have high moisture levels of 55-78% in my exterior shower wall. This is no plumbing in this wall. The shower deck is recessed 4 inches from slab and built on concrete sub floor. I have checked the attic and there is no signs of leaks. The stucco siding has minimal to no cracks in the area. The whole side of the house has a dry reading on a thermo and probe type moisture meter, except when using a thermo meter that shows moisture in the area of the walk in shower. What can be the problem? Where ro I start trouble shooting to isolate where the moisture is coming from?

 

[Alastairreid]

probe metres are ineffectual on masonry substrates! which are primarily designed for testing the moisture content of wood.

if the exterior wall is uninsulated and cold the moisture from the shower will condensate more readily on it giving higher readings.

in the absence of any other sources of water ingress or seepage the most likely cause would be condensation. look at mechanical extraction and increase ventilation to the room.

 

[JAXJOE]

probe metres are ineffectual on masonry substrates! which are primarily designed for testing the moisture content of wood.

if the exterior wall is uninsulated and cold the moisture from the shower will condensate more readily on it giving higher readings.

in the absence of any other sources of water ingress or seepage the most likely cause would be condensation. look at mechanical extraction and increase ventilation to the room.

This is a pre-existing issue. The builder has opened up the wall about 1 year ago and the cocoon insulation was soaking wet in that area. The tile was properly grouted and sealed. There didn't appear to be leaks. I haven't used that shower now in two weeks and still have a wet wall. The thermo meter that shows cool and hot zones shows the wall being in warm range and cold in that one particular area.