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Blown cellulose in soffits now causing leak

Jason Shapiro | Posted in Energy Efficiency and Durability on

I had blown cellulose installed in my attic last week with sprayfoam sealing of the top plate and Styrofoam baffles placed between each rafter. I also had dense-packed cellulose installed in between each stud in the wall below. We have now had significant snow fall and freezing rain, and today I noticed a leak from the top of a window casing in the wall that was dense-packed. When I went up on a ladder to look at the gutter, I found a significant amount of frozen cellulose protruding from a gap between the slate roof tiles and the sheathing underneath. It appears that this cellulose was wicking water up into the soffit and/or wall, which was then leaking out through the window casing inside. The insulation contractor came back and used a propane torch to melt the frozen cellulose and pull it out where it was protruding, which will hopefully stop the capillary action that seems to be pulling water in from the gutter. However, the soffits appear to be filled with cellulose that is poking out through the vents, and which can be easily seen from the outside of the house. I am also able to reach up through and behind the gutter and under the sheathing and can feel a large amount of wet cellulose. The contractor is saying that there must have been a problem with the roof that allowed the cellulose to communicate to the exterior in this way. He is also saying that there is no need to remove the wet cellulose because it is treated with borate and will not mold. My questions are:

-Is there any reason to have the soffit and or wall opened up to remove the now drenched cellulose?

-Could this have happened if the soffit vents in the attic were not adequately blocked (they did block them with fiberglass)

-If the baffles were not properly installed, or

-If the top plate whas not adequately sealed with spray foam?

-Could this have been caused by a pre-existing roofing problem, and if so, was there any way to know this before the insulation installation?

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  1. GBA Editor
    Martin Holladay | | #1

    Styrofoam baffles are flimsy and are the wrong type of ventilation baffle to use in this application, especially for a home with slate roofing over skip sheathing. I'm guessing that the cellulose if finding its way through the cracks at the sides of the flimsy baffles and is filling the spaces between the skip sheathing and slates. In addition, some of the cellulose filled your soffits.

    This is a mess, and the cellulose installer is responsible for making it right. If he doesn't come back to fix the mess, it's time to go to small claims court.

  2. Daniel Ernst | | #2


    The foam baffles that your contractor installed are designed to allow ventilation from the soffit into the attic (and then out of your attic vents, which are likely gable vents on a slate roof). This ventilation air is supposed to keep moisture from accumulating in your attic area.

    Depending on the size of your rafters, there is usually a vertical space between the top plate and the roof sheathing. Some baffles are designed to cover this vertical space. Some do not. I'm attaching a picture from the Energy Star website that shows someone using fiberglass batts to block the area below the foam baffle. IMO, this is not a very well thought out solution, but it sounds like this is how your contractor did the job.

    A few comments on your situation:

    1) It sounds like the cellulose installer did not adequately investigate the building structure before blowing the cellulose.

    2) Without some additional information, it's hard to say how the cellulose made it into your soffit. It could have been placed there during either part of the installation---the wall OR attic blow. The fact that your contractor wasn't able to figure out how this happened isn't very encouraging. But it's a moot point now. You need to move forward.

    3) Although treated with borates, you don't want to have sopping wet cellulose insulation hanging out in your wall cavities or your soffit. It will not dry quickly enough, and could lead to more serious damage. It's likely that you will have to open up your wall cavities to remove the wet insulation. Some judicious probing and testing with a moisture meter would help determine if this is the right path, and the extent of the "leak."

    By installing the cellulose in your walls and attic, you have decreased the drying potential of the structure. So you definitely want to get the insulation out of your soffit / vents, even if it's not wet.

    To help figure out next steps, I'd like to suggest you take the following pictures and post them here:

    * Soffit, from below. Show the soffit vents if possible.

    * Attic area, from inside, looking toward the eves. Show the top plate.

    I'm curious why the cellulose is peeking out from underneath the first course of slates. It's possible that your roof was "skip sheathed" and that there are gaps between the boards. This was fairly common in older houses. It might help explain this fact, if the cellulose arrived through the attic blow.

    Also, please clarify some issues:

    How was the top plate sealed? From inside? Fom the attic side? Was this spray foam in a can, which is used to seal small openings---or closed cell foam sprayed from a tank?

  3. Daniel Ernst | | #3

    Here's the picture of foam baffle and fiberglass batt:

  4. David Meiland | | #4

    Is that a 16" baffle in a 24" space?

  5. GBA Editor
    Martin Holladay | | #5

    That's common (16" baffle in 24" bay). You see it all the time. Doesn't make it a good practice, of course.

  6. Shane Claflin | | #6

    Its hard tell what happened there exactly without actually making a closer inspection up in the attic. Either way, the contractor performed work that has caused damage to your walls and the brand new product that you just had him install. Keep an eye on your wall surface above the window and look for damage. Take pictures. If he doesn't cover his work, as he should, you need things in writing stating that cellulose is shot once it takes so much bulk moisture (i.e. water). the work was shoddy. Take lots of pics. FYI, so much water will wash out the borate and make the fire retardent ineffective.

  7. Daniel Ernst | | #7

    David - Yep, that's what I thought. Courtesy of Energy Star:

  8. David Meiland | | #8

    The baffles we use have a little flap that folds down and staples on top of the top plate, to keep insulation from going outside of the wall line.

    What kind of rookie insulation contractor would blow a bunch of cellulose up under a slate roof like that? Just when you think you've seen it all.....

  9. Aj Builder, Upstate NY Zone 6a | | #9

    Why do people insulate in the winter??????

    Tell the contractor and your insurance company and your lawyer about the project. Keep the ball rolling. Don't do work like this again in the winter. Spring, Fall great.

  10. Jason Shapiro | | #10

    A few more questions that just occured to me:

    -Because the cellulose protruded through between the shingles and sheathing, is it more likely to have come from the dense-packing of the wall since that was done with pressure than from the attic installation where it was just blown in loose?

    - How could the cellulose have gotten from the wall into the soffit unless there was some defect with the way the top plate was installed? If there was some defect in the top plate, was there any way to detect that prior to the installation?

    -The installer today was saying that the flashing on the roof where it meets the gutter did not extend far enough into the gutter and that could have allowed the cellulose to escape, and that there must have been a gap there before the installation because there isn't enough pressure from the dense packing to lift the shingles up. Does that sound accurate?

    Thanks again

  11. GBA Editor
    Martin Holladay | | #11

    When you are installing cellulose in an old house, you can't make ANY assumptions. It's ALWAYS possible that the cavity you are filling with cellulose communicates with an adjacent cavity.

  12. Jason Shapiro | | #12

    Thanks Martin, So what could have been done by the installer to prevent this?

  13. Jason Shapiro | | #13

    Thank you all for the excellent responses. The contractor is coming over tomorrow to discuss, and hopefully they will agree to make it right.

    In response to Daniel's post I have attached several photos of the soffit vents from the outside, 2 showing the cellulose poking through, and one showing the water dripping from the soffit and hitting the outside of the window. I have also included several shots from within the attic looking toward the eves. The top plates are all buried in cellulose so are not visible. They used closed cell foam from a tank on the inside of the attic to seal them. It does not look like skip sheathing, but tongue and grove with some small gaps in between.

    I hope this helps explain the situation a bit better. Any additional advice based on this? Anything that could help me work this out with the contractor would be much appreciated.

    Additionally, there was a gable vent on a higher part of the roof line that communicated with the section that was spray foamed, and they closed off that communication with foam so that the section they worked on no longer communicates with that gable vent. How important is is that this communication be reopened, or is there another form of venting that can be installed on a slate roof?

    Thank you again.

  14. GBA Editor
    Martin Holladay | | #14

    It may not have been preventable (although sometimes cellulose installers stop blowing when a cavity seems to require more insulation than expected, and sometimes cellulose installers have a helper keeping an eye out for examples of cellulose popping out where it doesn't belong).

    But whether or not it was preventable, the results are the insulation contractor's responsibility.

  15. Daniel Ernst | | #15


    In your third picture you can actually see the cellulose blocking the foam vent---the left side.

    That said, I think it's very likely that the majority of the cellulose under the slates (and in the soffit) came from the wall blow. There's just too much of it---and it appears to have been forced into place, from the dense pack operation.

    Are you even sure that the walls had top plates? Older houses were often balloon framed, didn't necessarily have continuous top plates.

    On a typical slate roof, flashing is not required at the eaves (or the gable end). The starter course of slates, installed back to back, creates the drip edge at the eaves. Don't let this insulation contractor tell you how to detail a slate roof. Here are a couple of links to show you what I mean:

    It's not clear to me why the cellulose exited below your starter course, unless the facia didn't form a tight joint with the roof sheathing. Keep looking, and you'll figure it out. In any case, the cellulose should have never made it that far, period.

    Your contractor needs to resolve ALL of the issues to your satisfaction.

  16. Charles Shade | | #16

    Any chance that something like this could be going on?
    Where the sheathing stopped at the bottom of the soffit for some reason.

  17. Robert Hronek | | #17


    I was thinking about something similar, some type of leak from the wall in the soffit allowing insualtion in to the sofit.

  18. Adam Zielinski | | #18

    I agree with Charles Shade above. I've seen this before where the outside soffit is lower than the inside interior ceiling. You can't be sure that the sheathing is intact and insulation won't get into the soffit.

    Sometimes if you are drilling and blowing from outside, you don't get full insulation coverage above the windows and doors unless drill and blow them from the inside, because you can't get above them from outside.

    I think the reason for the cellulose leaking out is from the wall insulation leaking into the soffit. While the vent baffles in the attic aren't very good, they are minimally adequate and with the fiberglass batt there, they are probably blocking all the attic insulation from getting into the soffit.

    The insulation is probably coming out of skip sheathing on the exterior wall inside the soffit. An easy miss for a contractor without a lot of experience. No good way to baffle that or avoid it either. You'd have to take apart the soffit and patch up the exterior wall and then rebuild the soffit.

  19. David Meiland | | #19

    The photo with the fiberglass batt is not the job in question.

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