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Moisture underneath main queen mattress

Discussion in 'Mid-Size Boats' started by Helli M, Sep 3, 2017. Add this thread to a FAQ

  1. Helli M

    Helli M

    Joined Sep 3, 2017
    3 posts, 0 likes
    Catalina 320
    CA Victoria BC Victoria BC
    Hi. Re 2003 Catalina 320, we get a fair amount of dampness underneath our queen mattress after sleeping overnight. Board above water tank damp too and will attract mould if we don't air it out each morning. Does anyone have the same problem? I have mattress cover as well as bottom sheet on top of mattress. Any solutions ? Thanks :)

  2. Benny17441


    Joined May 24, 2004
    5,141 posts, 247 likes
    CC 30
    US South Florida
    It is hard to say as there are many variables but it seems there could be a condensation problem at the partitions that separate the interior of the hull and the interior of the cabin. While there is usually some water trapped in the hull stringers below the sole of the cabin an excessive accumulation could lead to increases in moisture throughout the boat extending to the stern and bow of the boat. Do you have rain leaks? Do you wash the deck frequently or take frequent showers inside the boat? It is a verified fact that using a propane heater or stove aboard induces humidity into the air. A person's breathing warms the air and adds humidity when exhaling which is significant over a period of hours. Ventilation usually reduces the problem if air flow can be directed to the problem area. It is hard to get proper ventilation when the air outside is cold and you are trying to warm the cabin to a comfortable temperature. This differences in temperature promote condensation. What can be done? Dry the boat by running a dehumidifier when at the dock, fix any leaks for either rain or plumbing, minimize the use of hot water in the cabin and create an air cross flow. Use fans to maintain air circulation (remember air does not flow around bends on its own). Basically think about all the ways humidity may be induced inside the boat and try to minimize their effect. Use fans and cross ventilation to promote air flow and try to maintain as little a temperature differential between boat compartments.

  3. jssailem


    Joined Oct 22, 2014
    2,897 posts, 544 likes
    CAL 35 Cruiser
    US Salem, Moored Port Everett WA
    Look at the "HyperVent Mattress Pad"
    I had a similar issue. This resolved it on my boat.

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