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Community and Q&A

Water-damaged ceiling — Tongue-and-groove ceiling installation

Steve Metsker | Posted in Energy Efficiency and Durability on

Hello. I have a 60’s mid Century modern home in Zone 5a and had a leaky skylight cause some water damage to my currently drywalled ceiling. Part of the drywall is damaged and the old skylight needs to be covered up as it was eliminated after multiple attempts to fix it. I would like to get the insulation right before replacing the ceiling with tongue and groove pine. It appears that all that is above the sheetrock are foil faced fiberglass batts. This room sits behind my garage and the ceiling is vented into the garage. The other end continues down the slope over my screened porch and there appears to be no venting in that soffit and no ridge venting either. There is a considerably large gap I can see between the roof and the current insulation through the venting in the garage. Obviously I would prefer to not have to remove the entire ceiling but the room is generally freezing cold in the winter so I would like to take steps to correct that. Thank You!

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  1. GBA Editor
    Martin Holladay | | #1

    Here is a link to an article that will explain all of the different ways to insulate the type of roof assembly you describe: How to Build an Insulated Cathedral Ceiling.

    Note that you can build an unvented roof assembly or a vented roof assembly. Either approach can work, as long as you get the details right.

    Also note that if you decide to install air-permeable insulation (for example, fiberglass batts, cellulose, or mineral wool) in your ceiling, you must have a good air barrier on the interior side of the insulation. Tongue-and-groove boards are not an air barrier, so this type of roof assembly usually needs a layer of airtight drywall, followed by tongue-and-groove boards on the interior side of the drywall.

  2. KeithH | | #2


    Depending on who is doing the labor, stapling and taping a membrane could be much easier and less vulnerable to future water damage than drywall. Check out Proclima IntelloPlus or Siga Majpell. You install these membranes on the bottom of the joists after batt insulation (or before blowing cellulose). They aren't inexpensive but the skill set to install them is pretty easy.

    Second, if you are doing the insulation install, look at Roxul ComfortBatts as a high performance alternative to fiberglass. Though it is time consuming, Roxul can be shaped more effectively to odd widths and such than fiberglass. Additionally, generally the friction between the batt and a 2x6 batt is adequate to stay in place until a membrane or drywall goes up (doesn't work with 2x4 batts). Of course, in most climates you'll need more than one R-23 2x6 batt, joist and attic space permitting. 2 R-23 batts fit nicely stacked in 2x12 joist bays if that's your joist sizing (typical for your vintage perhaps) to give R-46, which is still inadequate in most areas but maybe all you have room for. Personally, I think they also are good at sound absorption. One downside: it us very hard to run electrical wire through it after the fact (but easy enough to install around existing wire).

    Full disclosure: I am a DIYer not a pro.

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