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Wet insulation in ceiling…possible moisture from mudding?

1stHouseBuild | Posted in General Discussion on February 21, 2020 10:59pm

Working on the new house that I’m having built (I’m trying to do as much work as I can along with the contractor and crew). We have cathedral ceilings. From inside out: sheetrock, fiberglass bats, styrofoam vent baffles, sheathing, synthetic roofing felt, standing steam roofing. 

The past two weeks or so the entire interior was sheetrocked, mudded, and painted. 

I’m now installing puck lights in the ceiling. I did half the house no problem, but now working on the other half and I’ve ran into soaking wet insulation. I reached up into the holes I made for the lights and the entire underside of the baffles is wet and dripping into the insulation. 

Now, one theory is that water is sneaking in due to the fact that we didn’t get the ridge vent on yet. That said, that seems like an odd way for water to get in, as while some water could get under the standing seam, it’s have to find its way down the roofing felt and…into a staple hole? And then through the sheathing? And then onto the underside of the baffle? 

So that seems like an odd route for water to get in. 

As such, is it a valid theory that all this moisture is simply all moisture that got pushed out of the mud? They had huge heaters running for about two weeks to help dry out all the mud and I wonder if a lot of it (naturally) went up into the ceiling, hit the cool baffles (it’s been cold out), condensed and as we haven’t fully opened up the felt at the ridge yet, it just hasn’t had an easy way to vent all that moisture out yet. 

Is that a valid theory? 

Obviously, next step is to get that ridge vented and the cap on. We’ll leave the lights out to monitor things for a few weeks. Just wondering if that would be a common culprit for excess moisture in a ceiling right after mudding the house.

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  1. andy_engel | Feb 22, 2020 06:38am | #1

    It sounds likely that moisture from the paint and the mud is the source, but that doesn't describe the entire situation. How is that moisture-laden air getting into rafter bays? I suspect some serious air leaks.

    Also, what climate zone are you in? How thick is your insulation?

  2. oldhand | Feb 22, 2020 07:11pm | #2

    If your insulation is "soaking wet" I can't imagine it all came from the dry wall mud. Any chance those huge heaters you mention are propane fired? There are several suspects here but propane burning releases a lot of water.

  3. DanH | Feb 22, 2020 07:26pm | #3

    This is almost certainly condensation coming from moist air that is somehow getting up through the ceiling from inside the house.

  4. danbrassaw | Feb 22, 2020 11:08pm | #4

    Newly constructed buildings produce a shocking amount of moisture, as do propane heaters. Regardless of that, can light penetrations in a cathedral ceiling are going to make that kind of condensation a long term problem. They're difficult to air seal well, and nearly impossible from the living space side.

  5. jlyda | Feb 23, 2020 02:36am | #5

    Most likely the moisture is from mud and paint. It’s a crazy amount of moisture that will never be duplicated again. Condensation is at its worst in cold temps as well. I hardly notice moisture when building in warm weather, but in winter it’s very noticeable. We typically keep temp as low as possible for drywall/paint to cure to minimize the condensation issue. The more extreme temp from inside to outside, the more condensation. If you get a warmer day open the windows and run a few fans, that helps get a lot of moisture out. If temps are cold, but not extreme may consider cracking a few windows regularly and running a few fans.

  6. 1stHouseBuild | Feb 24, 2020 12:01pm | #6

    Thanks, all. One other bit of info to add to what I think makes sense to the theory that this is all interior moisture from mudding/painting...we never cut open the housewrap at the ridge (which we'll do this week). So my thinking is that all that moisture got up in the ceiling, but without the ridge vent fully opened, it didn't have anywhere to go. Hoping that once the ridge vent is open most of the moisture will find its way out.

    As for the lights...these do have gaskets and seem to have really strong spring clips that appear to give a pretty solid seal. That said, would it make sense to just remove the gasket and caulk these things?

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