Stateroom moisture

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This topic contains 3 replies, has 4 voices, and was last updated by Tom Easterbrook Tom Easterbrook 4 months ago.

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    The bottom of the mattress in our 37 ‘ Nordic Tug, Hull #1 is collecting moisture. We can find no leaks, and the bilge is not very damp.

    A dri-z-air moisture collector placed under the berth accumulates about 1/2” of water in about 10 days.

    The mattress is beginning to get mold stains.

    Any thoughts?

    Thanks, Jay

    Bill Robertson
    Bill Robertson

    Hi Jay,  I would suggest the first thing you do is make sure there’s no leaks.  If none then the next step would be to elevate your mattress to allow air to circulate underneath.  We use Hypervent under our mattress and have no issues thus far.  This creates about 3/4″ space under the mattress for air circulation.  I know some people that when they are not on the boat raise their mattress up a couple inches in 2x4s to help with air circulation.  You might also consider a powered dehumidifier.  I run one all winter.  It keeps the humidity in the boat around 40%.  Any less that that can cause the teak to dry out and crack.  I also leave my engine room hatch slightly open so the boat is able to breath through the engine room vents.  I run my block heater in the winter to add a little heat to the fresh air.  While you’re doing all this you need to kill the mold before it gets out of control.  After you treat the mold I’d think you could flip the mattress over so you can keep and eye on it.  Since I haven’t had a mold problem I don’t have a specific product to recommend for killing the mold.  You can check the label on the mattress for the manufactures info and contract them for help with products.  Hope this helps.

    Jonathan Seymour
    Jonathan Seymour

    Hi, Jay.  Same problem.  On our previous boats would always wipe dry under the mattress every morning.  For no good reason, we did not do this last year.

    Result was entirely predictable.  In spite of hypervent – a wet mattress, and rampant mould.

    Treated with “Mold Out” several times.  Then sprayed with “303 Fabric Guard.   Not necessarily a good idea.  Mattress refused to dry.  Was considering replacement.

    Left it all winter with a fan heater sucking ambient air in through the hawse pipe and blowing warm air over the mattress.  After several months it has finally dried off.

    Will now see how things develop.  Mold appears to be dead.  Stain remains.  Will wipe under daily.



    NornaJ 37/97


    Tom Easterbrook
    Tom Easterbrook

    Hi Jay,

    From my experiences over the  years (on 2 different boats) and some research I have done, there are two schools of thought (maybe more) on the prevention of mold over the winter storage season. One is to close up the boat (as best you can) and run a dehumidifier, fans, or small heaters (could be just an Oil pan heater – Wolverine, with the engine hatch left open). The other method is to ensure a steady stream of air movement through the boat (for example, intake air at the bow and exit at the stern). Both methods of course depend on there being no water leaking into the boat and dry bilges (as much as possible).

    I have had great results during winter storage using a dehumidifier in the galley (draining into the sink), leaving all floor hatches open, running a 200 watt Wolverine oil pan heater (engine), closing over the ER vents, using 2 DryZ air units in the master cabin, 1 DryZ air in the second cabin, and a small electric heater in the master and salon. All cabin and cabinette doors are also left open. I turn all mattresses monthly and use the Hypervent product under all mattresses. This results in indoor temperatures in the high 50’s to low 60’s and a humidity level around 40%.  I have so far, had no mold or moisture problems using this method. I did similar on my previous boat for 11 seasons, same result.

    If you use your boat in the winter, realize that breathing and cooking produce huge amounts of moisture (humidity) that must be dealt with. Usually this involves providing good ventilation and air flow, or running a dehumidifier. Get rid of the mold as soon as possible, dry everything out, seal up any leaks, and decide on the best method of prevention for your situation.

    I hope this helps,

    Tom Easterbrook

    Pilitak NT 37-068

    Nanaimo, BC

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