Do We Have a Leak to the Floor or Not?

[emelaich]

Using a General moisture meter--pinless type--we're getting about 25 - 29% moisture reading in a small area about 8" across just inside the L side of the door on our 2017 25' FC FB. Elsewhere, it's between 0 and 8% give or take.

It's damp here with no recent rain. Took out the threshold so we could examine under the vinyl flooring and there's no tactile difference between the 'wet' area and the dry just a few inches away. Confounding the issue is that it's dry next to the wall but going about 3" in, we run into those bigger numbers, yet groping around under the vinyl there's no difference in the way the wood subfloor feels.

Moving outside, just inside the void where the steps live when folded up, there's a finger or two access to the Mylar faced insulation. Wondering if I should just drill out a half dozen rivets and remove the black painted aluminum sheet, slit the Mylar and see what's up from the underside?

The percentage seems to go up and down with the varying humidity outside and yet, just that one area's affected.

We've done a couple of leak tests and added some caulk around the upper and lower belts in that area but nothing on top's blowing bubbles and there's no evidence of anywhere water could get in. The other side which would mirror the suspect area tests at 0% so I'm guessing that maybe the flooring's just absorbing some of the outside moisture without actually being wet.

Considering getting to that area above the Mylar and hosing it down with Thompson's. Any ideas/suggestions? Had the vinyl propped open with a fan blowing on the subfloor in that area for several days with little or no difference.

Thanks!

[skyguyscott]

Normally, the first thing I would do in troubleshooting is to look at the instrumentation itself and how it is being used to confirm 1) it is working correctly, 2) it is being used correctly, and 3) the environment in which it is working is not interfering with or fooling the detectors.

Sometimes the instruments or tests we perform can give false readings, and so we always have to first ask, is there really a problem, and if so, is it with the equipment or with the actual test subject?

Without knowing exactly how your moisture detector works, I would see if another detector, preferably one that works differently, also senses the moisture, or if there is something that could be throwing it off, like, i dunno, a water line, a refrigerator defroster, an aluminum reflection...?

The point being, that before I start taking apart the trailer, I would try to understand why the detector is acting the way it is first. Could be right, or it could be wrong.

[Al and Missy]

Get an inexpensive pin-type meter and use that to double-check your measurements. Amazon has one with a remote probe that is handy. The pinless types could be RF or ultrasound or ???. RF and ultrasound could be affected by many things, potentially including a void in the plywood.

Al