Should I do a PMF leak test?

[EKHudsonValley]

Hello!
First time poster and builder here. I'm about 90% through building a custom camper using the rigid insulation panel + Poor Man's Fiber Glass method, although I also have some light framing inside made of mostly 2x3's.

So, I recently learned that PMF is more water resistant than completely water proof, even with the exterior house paint coating (I did 4 coats, the first being diluted 50/50 with water, the second and third being 75% paint/ 25% water, and the last being full paint). This is because we had some torrential rains all day and the water pooled in the little indent caused by the windows pressing in snug against the PMF, which I had not caulked. Over the course of the day, the rain seeped in through the PMF. I see it was a noob mistake, in retrospect. I've caulked around the windows and made sure it was really smooth so there are no more idents and was able to dry it out well inside.

Should I now run a test? I was thinking of putting the sprinkler on to simulate rain and seeing if anything leaks. Has anyone tried that? Good idea? Bad idea? I don't have a garage, so it needs to be able to hold up to the elements (I did get a snug-fitting cover for it).

I found a gallon of unused Zinsser Watertite ultra I had laying around and was wondering if it would be good to apply that. Would love to hear from more seasoned builders!

 

[Pmullen503]

................This is because we had some torrential rains all day and the water pooled in the little indent caused by the windows pressing in snug against the PMF, which I had not caulked. Over the course of the day, the rain seeped in through the PMF. .........

Water may have entered between the window flange and the paint soaked canvas. (I'm assuming the windows were mounted onto painted canvas.)

But normal latex paint is not "waterproof" it is in fact a good house paint because it is permeable to water vapor. So you should not let water pool anywhere if you can avoid it.

More coats makes it less permeable. (And fills the weave more too.)

 

[Stovlar]

I wouldn't run the sprinkler over it to test it for leaking, I would blast it with water to be sure it's not leaking.

 

[EKHudsonValley]

Water may have entered between the window flange and the paint soaked canvas. (I'm assuming the windows were mounted onto painted canvas.)

But normal latex paint is not "waterproof" it is in fact a good house paint because it is permeable to water vapor. So you should not let water pool anywhere if you can avoid it.

More coats makes it less permeable. (And fills the weave more too.)

Yeah, I think this is what happened.