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Spray foam problem

jimruss75 | Posted in Energy Efficiency and Durability on

Hi all,

I am having a problem with a closed-cell spray foam install from a few years ago.  I hired a contractor to spray foam the rafters.  This tightened the house and brought the attic storage space within the conditioned envelope of the house.  We are located in Rochester, NY.

The second floor has a knee wall of about 5′, then a sloped ceiling, and finally the attic.  In order to spray foam the sloped ceiling, the contractor temporarily removed the roof shingles and sheathing from that area (as opposed to removing the plaster on the inside).

Now, every winter I get this brown stuff dripping down the siding of my house.  It only happens when we have a thaw after a deep freeze.  The dripping never occurs during warm weather.  It does not happen everywhere.  The attached image show the worse area.  There are a couple of other areas that drip, but are not as bad.

We do not notice any water damage on the interior of the house.

I guess I need to get up there and start taking stuff apart to see what is going on, but has anyone see this condition before?  Any idea what may be causing this?

BTW, I am not asking the contractor to come back because we had a falling out with him.  He did a terrible job of patching the roof and we had to replace the entire roof that wasn’t that old.

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  1. Expert Member
    BILL WICHERS | | #1

    Your contractor installed the foam “backwards”. Spray foam needs to be applied to the underside of the sheathing in an invented assembly, which may be what you have here. If the contractor installed the spray foam from above, you have a gap above the foam with a condensing surface under the sheathing. My guess is moisture is making its way into that gap, freezing, then thawing and running out the soffit vents which is what you’re seeing.

    This is a bad thing. You probably have rotten sheathing which is where that brown coloring is coming from. I’d recommend having a roofer check that.

    You may be able to open the roof again and make sure there are unobstructed ventilation channels from the soffit vents to the ridge vent in every rafter bay. Chances are the spray foam contractor sealed some of them enough to cause these problems. If you’re able to convert this over to a properly vented roof assembly you’ll probably be ok, but you’re almost certainly going to need to replace a decent amount of the sheathing on your roof.


    1. jimruss75 | | #2

      Thank you for the reply, Bill. Just to clarify, the roof was converted to an unvented "hot roof." Which is to say there are no ventilation channels. In the attic area where the rafters bays were exposed, the contractor spray foamed directly to the underside of the sheathing.

      In the sloped ceiling part of the roof, the contractor convinced me that it would be better to spray foam from above by temporarily removing the shingles and sheathing rather then disrupting the interior finishes.

      I get what you are saying that the spray foam in this area is on the backside of the plaster rather than directly on the sheathing, and thus there is likely an air gap between the foam and the sheathing. If the interior air is leaking into this space somehow, then it will condense on the sheathing, freeze, and then thaw and drip out the soffit onto the siding.

      1. vap0rtranz | | #15

        >In the sloped ceiling part of the roof, the contractor convinced me that it would be better to spray foam from above by temporarily removing the shingles and sheathing rather then disrupting the interior finishes.

        Sounds odd.

        Our contractor who did the spray foam sprayed directly to the underside sheathing of the roof. We also have 5' knee wall on 2nd floor -- and lath and plaster at that. So for the sloped ceilings, all the contractor did was remove the sloped ceilings. The lath and plaster were a mess but they did a professional job of getting it out. Drywall ceiling would probably be even simpler.

        What kind of interior finishes would have made removing ceilings MORE difficult that opening up a roof?? Is it a wood panel / plank style ceiling instead of drywall / plaster?


        1. jimruss75 | | #16

          The finish is plaster on a gypsum board base (as opposed to lath), with curved transitions from the vertical wall and the horizontal ceiling. Removing the plaster would have disrupted three bedrooms, a playroom, and a bathroom. Plus the curved transitions would have been hard to recreate. At the time, it made sense to spray from above, but that itself ended up being very problematic.

    2. GBA Editor
      Brian Pontolilo | | #3

      Have you seen this situation before, Bill?

      1. Expert Member
        BILL WICHERS | | #4

        Not with spray foam, no, so it’s an educated guess on my part. I’ve seen similar situations when water can get inside a roof assembly slowly, then freeze, then run out when things thaw. It’s like an ice dam in reverse.

        I can’t think of anything else that would be causing what the OP is seeing. The best test I can think of that wouldn’t be hugely disruptive would be to lift or remove a shingle or two, use a hole saw on cut a smallish access hole, then either use a borescope or shine in a flashlight. If the top of the spray foam in the “backwards” area is wet, then we know what the problem is.


        1. GBA Editor
          Brian Pontolilo | | #7

          That makes sense and this is going to take some invasive investigation no matter what.

      2. Expert Member
        NICK KEENAN | | #27

        I saw staining very much like that once when the siding installer had put a nail into a drain pipe running down the wall and sewage was leaking. But it looks like it starts too high in this case.

        The point is, it could be almost anything.

  2. 730d | | #5

    Can you gain access to the little triangle attic and look up to see the path of the flow? I have seen very similar staining on sidewalls in Minnesota that had 1/2" black fiber sidewall sheathing.
    It looks like your soffit is stained though.

  3. DavidfromPNW | | #6

    It's probably generating condensation in the sloped area for the reasons Bill pointed out. Below the sloped roof where it is spray foamed to the underdeck, the water is building up (damned up) until it reaches the level of the roof decking seams and is leaching out the seams and running down the top of the de king and underneath the tar paper which explains the color.

    I'd further hypothesize this as it is clearly coming from behind the gutters and is not subject fo the drip edge, again leading me to believe the condensation is coming from under the shingles and on top of the roof deck leaking out of the seams on the sloped area where gaps remain from installing tot he drywall as opposed to the roof deck.

    Caveat: I am not a contractor and I could be wrong, but this looks total sketch to me.

  4. Expert Member
    Peter Engle | | #8

    No doubt about it. Interior moisture is finding a cold surface, condensing and freezing. When the weather warms up, it melts and runs out the soffits. The brown staining is probably "wood tea" which happens as wood rots and the water soaks up tannins and other wood solids. It is almost always a sign of structural decay.

    It's probably happening where the contractor sprayed the foam against the ceiling, leaving a gap between the foam and the roof sheathing, as Bill suggested above. It is also possible that it's happening at the eave/soffit area. Warm/moist air from inside the walls can come up through holes for cables, plumbing, etc. if they didn't foam all the way down and over the top plate. The foam dams this airflow from going up the roof, and it vent out the soffits instead, but the whole roof/eave/soffit area is cold because of the spray foam inboard of this area. So, the moisture freezes right in the top of the soffit area.

    You really need to find out where the condensation and ice are happening and how bad the damage is. Depending on how bad it is, you might be meeting with an attorney soon.

    1. DavidfromPNW | | #10

      Just doing my napkin forensics on the photo, I highly doubt it is this,

      " It is also possible that it's happening at the eave/soffit area. Warm/moist air from inside the walls can come up through holes for cables, plumbing, etc. if they didn't foam all the way down and over the top plate."

      From them pic, the pattern kinda suggests to me that it is coming down the the roof line, not the wall. If it were the wall, I think you'd see this either behind the siding altogether, or you'd see a a pattern where the horizontal seams were leaching instead of the clear dripping down on the outside from one piece of siding to the next as evident by the lack of brown stuff right below the the horizontal seams.

      Additionally, you'd have to be actively trying not to cover the top plate to leave it unfoamed. Just the overspray alone should do it. Given that the contractor went to such an effort (albeit wrong) to foam the slope, you'd think they wouldn't much that up. I am really curious to find out what happened here.

      edited: one other thought, if it were coming up the wall, with this volume, I'd expect to see ceiling drywall issues. OP, are you seeing anything inside?

  5. 730d | | #9

    One of the hardest things to do for me is keep an open mind and investigate and keep an open mind and investigate and keep an open mind and investigate. That being said it could be from something stupid like a bathroom fan or a disconnected heat duct or a humidifier run wild.

    No doubt about it. You are likely correct Peter. Where is the moisture coming from? Maybe the foam guy blocked an earlier ventilation route. Keep an open mind.

  6. jimruss75 | | #11

    Sorry for the delay in my follow up. We're dealing with Coronavirus issues here. Anyway, a few more points:
    > There are no signs of staining or water damage from the interior.
    > This is a balloon framed house built in the 1940's.
    > The brown dripping does not occur all around the house. It only occurs as shown in the image and a couple of other smaller locations. Wouldn't that indicate that this is not necessarily a "detail" problem, but rather an installation problem in a few spots?
    > For what it's worth, the vinyl siding in the image is on top of 1" EPS insulation, which is on top of the original cedar clapboards.

    Once the weather warms, I will start the process of disassembly (remove the gutter, soffits, some roof shingles, etc.) until I discover the problem.

    How difficult is it to temporarily remove asphalt shingles to be reinstalled later? I'd never be able to buy new shingles to match the existing.

    1. user-723121 | | #12


      Saving shingles can be done depending on the type and how stuck together they are. Shingles on the southern exposure are the first to show aging and can become an asphalt block due to the summer heat. If you are trying to save the shingles, start at the top, remove the nails and slide a flat bar under each row to shear the adhesion. The reused shingles may not seal down as well as they did originally. Another problem can be the roofing nails are over driven (hard to remove) because the typical roofer has no regulator on the air compressor.

    2. Expert Member
      BILL WICHERS | | #13

      You can sometimes use a large drywall knife to separate shingles that have become glued together. You need to use the drywall knife to slit between the shingles and gradually work them apart. What you need to avoid doing is bending or flexing the shingle too much or it will crack and fail.

      If you’re unable to salvage enough of the original shingles, you can sometimes interleave some new shingles with the old shingles you’re able to salvage. If you do this interleaving over a large enough area, it can be made to look like an intentional design pattern instead of an “I couldn’t find matching replacement shingles” kind of problem.


  7. JC72 | | #14

    What about convection currents inside the exterior wall?

    Could moisture travel up the inside of the exterior wall condense/freeze onto the sheathing and then thaw traveling down the underside of the sheathing following slope of the roof where it drips onto the soffit vents?

    1. Expert Member
      Peter Engle | | #17


      That's pretty much my expectation. The OP says this is a balloon-framed house, though there wasn't much true balloon framing still going on by the 1940's. Still, I'll take his word for it.

      With balloon framing and without proper fire blocking, there are wide open stud bays that can carry moisture from the basement to the roof. Holes in the top plate (if there is a top plate) can allow fountains of warm/wet air up into the soffit area. With some construction, there is a top plate, but no continuous sheathing, so air can short-cut the top plate and flow through the sheathing into the soffits. When the attic was open, this warm/moist air was diluted with outdoor air from the soffit vents and circulated in the unconditioned attic until finally going out the ridge or gable vents. Once the spray foam is installed, that's not happening anymore. The moisture is trapped in the soffits, it condenses then freezes on the underside of the sheathing, then melts when the weather warms up.

      The reason this only happens in certain places can be as simple as those being the only unblocked stud bays. Or, as Mike says above, it could be a bathroom fan venting into that soffit. We can't know for certain, but opening up the area for investigation should help.

      Sorry to hear about the coronavirus thing. We're all going to be dealing with this for a long time.

  8. Underwood_C_and_P | | #18

    I am an electrical contractor and have installed many home and bath fans. Although your eaves are rather short, the soffit is a continuous vent panel. Every energy consultant I worked with always cautioned against venting under the soffit surface as humid air will rise into the vented soffit panels. Are these spots located above high humidity areas. Just a thought.

    As far as the issue of removing the shingles, it is a tedious endeavor. I agree with the comments on that to this point. I would add that the tabs will be easier to lift away from the shingle below the warmer they are but be careful as the shingles will tear more easily when their hot.

    I have used a flat pry bar to slowly get under the shingle to start to lift the nails, then lift the nail from the surface with a curved "Wonder Bar" once you can get under the head. Start from the top of the area to open. Sometimes you can use a thin flat bar once you have exposed the nails.

    Upon reassembly, don't renail in the old holes if any damage has occurred. Use a good quality roofing caulk to seal old nail holes as you go to keep driven rain from getting in. I have used a dab of caulk to reset the tabs of the next shingle where the strip has been damaged.

    My advice is take it slow and you may be successful on a small area, but if the roof deck is questionable then you may have to tear that whole roof section off and I would hire a professional for that. Remember, wood rot begets wood rot. If any is left behind, more will grow.

  9. 730d | | #19

    I am only guessing. The foam probably blocked ventilation that previously mitigated a multitude of sins.

  10. yankees177 | | #20

    James did you ever figure this out. I had standard closed cell spray foam recently installed a month ago and I am seeing this in a few areas and I am getting nervous. Also in upstate ny and it's happening as you describe. But only in a few areas.

    On top of this I now have condensation on all of my windows that I never had before. Kind of regretting doing this.

    1. Expert Member
      BILL WICHERS | | #21

      The condensation on your windows is likely due to higher indoor humidity levels due to less air leakage from the better air sealing you get after putting in spray foam. If you're running a humidifier, STOP -- that's the cause! If you're not running a humidifier, then you probably need some ventilation from something like an HRV.

      The dribbling could be due from mositure accumulation in the roof/ceiling. If you have a humidifer running, it could be the cause of this dribbling too. If you aren't running a humidifier, then you'll probably need to do some investigative work as described earlier in this thread.

      Note that "good" indoor humidity levels are generally under 40%, and that number falls with decreasing outdoor air temperatures in most cases.


      1. yankees177 | | #22

        Thanks Bill. Yes I understand I'm getting more humidity because of the better sealing. My house is so leaky that I never thought this would be the case. I am not running a humidifier however I grow some veggies indoors hydroponically in my "basement" (it's a raised ranch) which put off a good amount of humidity down there. I have a dehumidifier going down there and it's keeping my basement in the 30-40 % relative humidity. My windows are all very old (newest ones are almost 20 yrs wile some of the old ones are really old).

        I'd really not like to add an HRV because that's added cost and that electricity usage will negate any cost savings due to the spray foam but I see no way around it.

        I also have boiler heat so I assume without ducts that means more $$.

        I never had to run my bathroom fans let alone get condensation. Now we run our bathroom fans as much as we can.

        It probably doesn't help that the outdoor temp is well below freezing right now.

        I don't have any hvac people I trust either which doesn't help.

        Spray foam people are coming out to do their walkthrough I'm going to tell them about the dripping because it has to be due to air leakage somewhere.

        I noticed that most of the condensation sits at the bottom of the windows where the hat from between then windows comes in. Do you think that new windows would help?

        1. Expert Member
          BILL WICHERS | | #30

          You can build an "enclosure" out of polyethylene sheet around your growing area. You want "walls" and a "ceiling" of this material, with a simple door (could just be an overlapping flap of poly). This will help to contain the mositure to that area, which is probably good for your plants but will also help to limit how much moisture gets out to the rest of your house. My mom had a system like this in my folks' old house until they moved (they now have a small greenhouse).

          You can use a small fan (like a computer muffin fan) to blow OUT from this enclosure to the outdoors using some dryer ducting and a dryer vent. The slight negative pressure will help to keep the moisture from leaking out of the enclosure into your home.

          I'd try this "plant room" before an HRV, you might find it's all you need.


    2. ThirtyWest | | #23

      Is that tar paper above your siding? Hard to tell from the picture, but it looks wet. I have an hrv and it's quite cheap to operate.

      1. yankees177 | | #24

        Not tar paper. it's actually where the attic meets the 3 season room. It's leaking from underneath there. I'm thinking the contractor didn't seal that area off enough and the warm air from the 3 season room (which doesn't have a ridge vent) is warming it up and creating condensation. Have a walkthrough with the spray foam contractor and will bring that up.

        I have an ac unit in the attic and a boiler in the basement. I am not looking forward to the cost of an HRV. Also doesn't this basically negate having the spray foam done?

        1. ThirtyWest | | #25

          I wouldnt say that it negates having the spray foam. It should help with moisture in the winter. I'd be surprised if my hrv cost more than twenty dollars a month to operate.

          Have you looked in your attic and done a visual inspection? Is the roof vented?

          1. yankees177 | | #26

            Also cost of install of HRV. I have a natural gas boiler that's old but so far works well. That vents out through the ceiling. I have bathroom vents that connect to ducts and that vents through the ceiling. I have another roof vent for waste line.

            Other than that the attic is sealed R21 on (mostly as I think those pictures bare areas not sealed correctly).

            Most of our cost is electric in winter since natural gas is cheap. I no longer run a space heater in my office which sucked a lot of energy. I was really hoping to gain a lot of electricity benefits in summer relying less on AC usage which kills me in the summer but now I am just worried over the humidity coming in the summer.

            I'm stressing out so bad right now.

  11. jimruss75 | | #28

    In my case, the contractor did not do a good job ensuring that the spray foam was continuous and sealed. He would do one area, then come back later to do an adjacent area. There were numerous gaps at the junction between the two areas. The result, obviously, was air leakage. The warm moist air from the house would leak through the spray foam and condense and freeze on the underside of the roof deck. Then when it warms up, that frost would thaw, take on the color of the plywood sheathing, and drip out the soffits.

    The solution was to seal up the gaps, which is a real pain. The gap areas are not conveniently accessible and are not easily visible. A gap can be a small pin hole. It doesn't take much for air leakage to occur.

    One more note: an HRV is nice to provide fresh air for a really tight envelope. Though they don't consume much energy, they are costly to install, especially for a retrofit. Regardless, I don't think an HRV is applicable to this thread. In both my and Terry's issue, air leakage is the problem and an HRV will not help with that.

    1. ThirtyWest | | #29

      James, Glad to hear that you got your problem resolved. Yes, I agree that A HRV will not fix the air leak issues. I would be concerned though about the condensation on all of the windows. seems as though that would only get worse when the air sealing is corrected. Thats why I thought an hrv would help. Best of luck to yankees177

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