Damp on plywood under mattresses

Submitted: Tuesday, Jul 19, 2011 at 22:56
ThreadID: 87664 Views:10039 Replies:14 FollowUps:4
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I'd appreciate your advice here!

We drive a Coromal camper - the sort that winds up and then the beds pull out at each end. Has mostly canvas walls.

We get damp under the mattresses which I assume is due to lack of air circulating.

We've been propping the mattresses up high and letting the damp dry out. Unfortunately it never gets completely dry before we want to either go to sleep or pack the van up. Also the plywood is starting to discolour.

I've been searching thru archives of forums about this, and see that some people suggested putting a cotton blanket or outdoor carpet under the mattresses. Others suggested drilling holes in the plywood to allow for circulation.

We aren't keen on the cotton blanket or carpet as it would still let the damp in, just has something else absorbing the damp instead of the mattress.

The holes idea sounds good, but how do we drill them to work and still maintain the structural integrity of the ply???


do we need to look at painting something on the plywood (which is currently unsealed)?


can you offer any other ideas?

Thank you :)
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Reply By: didiaust - Wednesday, Jul 20, 2011 at 05:46

Wednesday, Jul 20, 2011 at 05:46
We drilled holes in the ply of our van bed and it worked . Hubby put 1" diameter holes all over the base - it is supported by a frame. We have 2 beds in the van and the only one we had problems with was the bed with the foam matruss. The bed with the innerspring was fine.

In our camper we have placed those large rubber tile mats( that have holes in them) under the foam matruss. Waiting for next trip in the camper to see if they work

AnswerID: 460377

Reply By: Member - Mark (Tamworth NSW) - Wednesday, Jul 20, 2011 at 07:31

Wednesday, Jul 20, 2011 at 07:31
Our previous CT had a foam mattress on a steel base, same problems with moisture, needed to be completely aired every 2nd day.
Problem went away when we ordered a "CT custom made" inner spring one from one of the manufacturers you see in the back of the CT Magazines. The mattress has air holes in the side.

We then bought a 2004 Kimberly Kamper with a foam mattress, but has holes about 50mm and problem still occurs, but to a far less extent. Needs to be aired every few to several days in humid environments

Suggestion is the holes in the plywood, or buy an inner spring mattress specifically for CT
AnswerID: 460379

Reply By: Member - res.q.guy (Vic.) - Wednesday, Jul 20, 2011 at 07:53

Wednesday, Jul 20, 2011 at 07:53
We had the same problem many many years ago with a Jayco camper.
We glued a builders insulating product on to the ply wood under the mattress.
Don't know it's name, but it came in 8' x 4' sheets, I think, and was made up of a 1/2" sheet of polystyrene with a silver foil lining on one side.
It was a little difficult to transport and handle, so I remember either cutting it in half or to size, at the hardwae shop to get it home.
It seemed to work for us.
AnswerID: 460380

Reply By: OLD PETE - Wednesday, Jul 20, 2011 at 08:25

Wednesday, Jul 20, 2011 at 08:25
Hi Lizzyb,
We had exactly the same issue as you, it is due to lack of air circulation, & the moisture not being able to evaporate away. Don't go drilling any holes, what we did was purchase a sheet of timber lattice from Bunnings, cut it to size, bung it under your mattress, & that will allow air under mattress to dry it out. Once we put the lattice under our mattress, we never had issues again.
AnswerID: 460382

Reply By: Member - Rob D (NSW) - Wednesday, Jul 20, 2011 at 08:47

Wednesday, Jul 20, 2011 at 08:47
EMP is a product designed to allow under mattress air circulation. We have it in our camper trailer and it seems to work well.
See the following link


Hope this helps.
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AnswerID: 460383

Follow Up By: TerraFirma - Wednesday, Jul 20, 2011 at 11:34

Wednesday, Jul 20, 2011 at 11:34
Looks interesting, not cheap though.!
FollowupID: 734074

Follow Up By: spudseamus - Wednesday, Jul 20, 2011 at 19:00

Wednesday, Jul 20, 2011 at 19:00
works great BUT is so expensive
FollowupID: 734109

Reply By: Bluefin48 - Wednesday, Jul 20, 2011 at 09:13

Wednesday, Jul 20, 2011 at 09:13
Hi Lizzyb74,
There is a product for preventing moisture under your mattress, we used it for years and never had a problem with moisture,another post gave the web site to it.
AnswerID: 460386

Reply By: Sawtybt - Wednesday, Jul 20, 2011 at 10:02

Wednesday, Jul 20, 2011 at 10:02
We also have the under mattress air circulation as mentioned by Rob D. Have been using it for 6 years in two different vans wihout any problems.
AnswerID: 460390

Reply By: lizzyb74 - Wednesday, Jul 20, 2011 at 11:15

Wednesday, Jul 20, 2011 at 11:15
Thank you for all of these fantastic replies - this is such a good forum!

We're going to try the cheap option first - lattice, and if that doesn't work for us we'll try one of these others.

Thanks again! :)
AnswerID: 460395

Follow Up By: member - mazcan - Wednesday, Jul 20, 2011 at 12:37

Wednesday, Jul 20, 2011 at 12:37
hi lizzyb
foam is synthetic and there-fore is a producer of humidy from our bodies heat creating moisture
i hadn't seen a foam mattress didn't
have dampness problem i have owned 3 caravans until i got camper trailer as mattress that comes from sweden and has aspecaial cover on it and is the only
one that has had no osture problem
i would go for the tried and proven remedy above as going the cheaper lattice could be doulbe the expense in the long run and the lattice eands wont be very kind to the bed clothes or your finger if you poke your hands into the cut ends of the lattice
FollowupID: 734081

Follow Up By: Member - Oldbaz. NSW. - Wednesday, Jul 20, 2011 at 13:47

Wednesday, Jul 20, 2011 at 13:47
We have doubled shade cloth under the mattress..cheap & it works....oldbaz.
FollowupID: 734091

Reply By: Roughasguts - Wednesday, Jul 20, 2011 at 15:12

Wednesday, Jul 20, 2011 at 15:12
Yep got this problem me self! So been thinking about it for a long while and wan't the cheapest lightest way out.

So I'm going to get some more of those black foam ground mats from Kmart and cut them in to 3 inch long strips and super glue them to get a strip as long as the bed, then use shorter strips to weave make it just like latice! but cheaper lighter and better on the matress and fingers. It should let the air flow better than just the mat alone.

AnswerID: 460414

Reply By: splits - Wednesday, Jul 20, 2011 at 20:19

Wednesday, Jul 20, 2011 at 20:19
My wife and I had this problem in a caravan many years ago. After being without a van or camper for about twenty years, we built a home made slide on and needed a mattress. We went to a company that made rubber cushions etc under contract for furniture manufacturers and asked their advice on the type of mattress we should buy and the moisture problem. We were told the moisture is caused by the type of foam. They claimed they could make us a mattress utilising two different density foams that would not get moisture under it.

We selected the rubber, they sliced it off huge blocks and glued it together. We have been using it in two different campers for nine years without any trace of moisture. It has been everywhere from the tropics to snow on bare plywood bases exactly the same as the old caravan. There are no holes or any other kind of ventilation or absorbent materials under it.

AnswerID: 460445

Reply By: rumpig - Wednesday, Jul 20, 2011 at 20:46

Wednesday, Jul 20, 2011 at 20:46
our Kimberley Kamper has a 12V heater under the bed for drying out the matress.... http://www.kimberleykampers.com/index.php?item=heaterandbedaccessories
AnswerID: 460450

Reply By: Member - Roger B (VIC) - Wednesday, Jul 20, 2011 at 22:11

Wednesday, Jul 20, 2011 at 22:11
G'day Liz. We had a Jayco Dove a few years ago, and it had 3 sheets of ply about 1 meter x 30cm under each matress . Not attached, just scattered. At first I wondered what they were for, but eventually found out. Never had condensation problems. The lattice should be ideal, and cheap. Good luck. Cheers.

Roger B....
AnswerID: 460467

Reply By: Member -Pinko (NSW) - Thursday, Jul 21, 2011 at 09:30

Thursday, Jul 21, 2011 at 09:30
Hello Lizzy
We have an Ultimate camper and it has a product called EMP mattress underlay and it prevents the problems you are experiencing. Used in fibreglass boats etc.
Just Google EMP mattress underlay.
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AnswerID: 460481

Reply By: lizzyb74 - Friday, Jul 22, 2011 at 21:36

Friday, Jul 22, 2011 at 21:36
Thank you!!
AnswerID: 460656

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