Wet bunk mattresses

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Phil Hyde

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We have discovered that the lower mattresses in our rear bunks are wet.  Immediately we thought "water leak", but we're stumped as to where it is coming from.  We are currently in Portland, OR, and it's been rainy since mid-Oct. 

Over the weekend we completely stripped one of the beds, but no water accumulated.  There was no visible water on any of the walls.  We switched mattresses, and now they are both wet again.

Given the persistent humid climate, is it plausible that these mattresses are sopping up enough moisture from the air to get wet?  Other contributing factors are the cool temps (40's at night) and the storage areas below the bunks are not insulated.

Thanks for any suggestions!
 
Condensation can produce prodigious amounts of water but it should be visible on the surrounding surfaces. A mattress can "wick" moisture from a source, but usually won't pull enough from air to be more than slightly damp feeling.

Try laying some newspaper in place of the mattresses and see if that picks up any water. Newsprint also picks up water well from most any source. If possible, get clean newspaper rather than printed - the ink runs easily when wet.
 
Thanks, Gary.  I think some experimentation is definitely in order.

I forgot to add that it's the bottom of the mattresses that are wet. 
 
Phil, this time of year the humidity in the Portland area is very high, almost 100%. With the cooler temps out side and the warmer temps inside and no insulation the bottom board will sweat just like a single pain windows. With the mattress lying on the wood it is soaking up the moisture instead of allowing it to evaporate. The only thing that might help would be to either heat the storage area or insulate it from the bunk area. Just some thoughts.
 
I think warsaw may be on the right track.  I would add that whatever you add below must have a vapor barrier first and then the insulation.
 
Can someone clarify where the moisture barrier should be?

Also, what if I installed vents under the beds so that the storage area is closer to room temp?

I haven't fully thought out the best solution.  It seems as though the bed construction is integral to the storage compartment.  Looking "up" from the hole outside, I see perpendicular pieces of wood that the horizontal sheet of wood (bed) lays on.  I was thinking this space could be closed in and insulated, but I don't know how much difference a 1-1/2" cavity would make.
 
Phil Hyde said:
Can someone clarify where the moisture barrier should be?

Also, what if I installed vents under the beds so that the storage area is closer to room temp?


I haven't fully thought out the best solution.  It seems as though the bed construction is integral to the storage compartment.  Looking "up" from the hole outside, I see perpendicular pieces of wood that the horizontal sheet of wood (bed) lays on.  I was thinking this space could be closed in and insulated, but I don't know how much difference a 1-1/2" cavity would make.

A layer of 1-1/2" rigid foam may be a very good option??
 
Hey Phil,
What was the outcome of your moisture problem?  Assuming you got it under control or found the culprit?

BTW, it's even colder and dryer than the last post here in MI!  ;)
 
Pretty sure this is condensation related, as it didn't get worse or better as the rains have varied.  At the moment, we're just tolerating it and running the dehumidifier in the bunk room more.
 
With any luck at all, you will find the problem before next years camping season and you will be good to go.  Unless your one of those year around travelers.  In which case, hope you find the problem and get it done.

Either way, best of luck.
 
If not moisture, then it could still be an external leak.

The best test method to find a leak is to us a garden hose on the outside, while a second person is inside.
Spray water on the side of the coach, starting at the bottom and slowly raising the spray up.

If there is a leak it will usually show up pretty quick.
 
Installed some insulation under the beds yesterday.  After a little bit of trial and error (initially thought using spray insulation would be easier, but it didn't stick), ended up just using regular R-13 wall batting with Owens Corning R-30 XPS sheathing.  The XPS was remarkably easy to cut (score and break).  The hardest part was contorting my body into the storage bays to install the screws.

Hope it works!
 

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