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Loud Noises From Unvented Cathedral Ceiling

scofike | Posted in General Questions on

Hi all – hopefully someone can offer some help on a serious issue we have. I recently bought a large log home outside Blowing Rock, NC that from the first night we stayed in it has made really loud cracking/crunching noises coming from the roof. Enough so that the first night I almost got out of bed to see if a bear was on the roof…its that disturbing. Seller had told us night before closing that the roof (which was metal when we bought it…more on that in a second) would make some “popping” noises in early evening and late morning, and that several roofers over the years told him roof was fine, its just what metal roofs do as they expand and contract with temp changes. Well, it is not little popping noise, rather it sounds like someone on the roof, and it happens almost all day and night (about 4am-9am is about the only quiet time). So we bit the bullet and ripped off the metal, down to the decking, and had new shingled roof put on….same thing, if not worse! Thought I was going to lose my mind. And this time, I noticed it happens not only with temperature rise, but wind as well. When we get some 20+ mph gusts, you will hear it almost ripple thru the house…like the whole roof is one big sheet (its actually three separate pitches…two rather shallow, one that’s 10/12).

It is an unvented cathedral ceiling with exposed beams 48″ on center, and T&G (I think 6″). Then there is about 4-6″ rigid foam board, then OSB and then shingles. If it helps, on the first day, after the roofers ripped off the metal roof, and got it down to the OSB, they took a lunch break, and I heard the noise even then…so it made noise without any shingles or metal.

Is it possible the foam board and/or OSB are not screwed down well enough? The roofers said the OSB was secured with long screws, not nails. And when they walked over it, it felt solid.

I am at loss. I have talked to 4-5 roofers locally and none have any idea. We have to fix this, and I know it will mean a re-roof, but we cannot stay in it, nor rent it out when it makes such scary noises all the time. I am actually going there tomorrow with the roofer to “biopsy” the roof by taking off some shingles and removing one of the OSB panels to investigate.  Will see exactly what foamboard is there, how thick, if its glued in, etc. Meantime, ANY help appreciated!

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Replies

  1. onslow | | #1

    Scofike,

    I have metal roofing and they do indeed pop in the sun, but gently. Even in our stiff winds the uplift rumble is quite ignorable. At risk of being alarmist, have you had a structural engineer review the roof assembly? The fact that you heard the same noises during lunch break leads me to question the overall rigidity of the roof assembly. Even with out snow loads to worry about, 48" rafter spacing sounds raises my eyebrows.

    You describe 6" T&G planking on top of the exposed beams. This sounds like the roofing used on some homes I saw built back in the 70's, which also had very wide spacing on the main house framing. Not quite full on timber framing, but nearly so. If I remember correctly, the roof planking was actually three 1x6 boards glued together to make 2"+ T&G by offsetting the middle board. This made them much stronger and more stable than milled 2x stock. The foam layer and then plywood formed the base for shingles. In the time I spent in three of them with friends, I never heard noises or had them complain about wierdness in the wind.

    Your description of the roof planes remains unclear to me, but if you imagine looking down onto the roofs and then imagine twisting them like a jar top, it may help you think about how the noises could be generated. The OSB on top of the foam may be set dead tight and the edges are doing something to make noise, but I doubt that. The first layer of T&G could make noise if the edges are dragging and popping from wracking forces. Hopefully minimum of two screws per board width. Weakly fastened boards would not be a good answer to find. It is possible that uplift is causing the rafters to move about in the sockets along the wall. Again, not optimal. Might want to get up close on both sides of the wall where they sit and check out the joints for signs of movement.

    Worse case scenario is the roof is either twisting or lifting in a way that could lead to failure in strong enough winds. A potential cure could be bracing provided by iron rods going wall to wall or however a qualified engineer decides is best. If it is any consolation, many of the big timber homes around me have them as a matter of course because people demand big open floor plans. Not a choice that is always easy to engineer without bracing. I would recommend trying to find a structural engineer or architectural firm with expertise in log homes.

    Is it at all possible that you are mis-hearing the sound location? A very tall wall broken by a big fireplace might prove wiggley enough to make the logs rub and creak.

  2. scofike | | #2

    Roger, thanks for the reply. I had considered having a structural engineer out, but actually talked to one today and when describing the problem, he was skeptical it was anything but the roof (i.e. not settling/foundation issues). And the person who inspected the house pre-purchase came out and looked it over again and saw no issues. So, its likely the roof. As for that, the roofer came out and we lifted up some shingles and pulled a screw and what we found is that the roof is unvented and its a sandwich of 1.5" T&G, 3.5" foamboard, and 0.5" OSB, for a grand total of 5.5". The screw we pulled was 5.5". Which means that the foamboard+OSB are secured to the T&G only, since the screw is not long enough to hit rafter. Its odd, though, because the screws are still only every 48" to align with the rafter. If there was no fear of poking thru and being visible inside house, I would think you could put more screws wherever you wanted since they would only go into T&G. But thats just how ours is.

    The consensus from roofer and inspector (former GC) was needs ventilation, but if you add a ridge vent and soffit vents, there is no air path...its completely filled with foam. One of the guys tried to claim that the foam could still "breathe" and that some air might pass thru, but I am skeptical. Anyone know if thats true?

    Options at this point are: pull up shingles above rafters only and drive longer (7"-8") screws all they way thru into rafter and re-shingle, and/or add ridge and soffit vents, OR just bite the bullet and remove shingles and OSB, lift up OSB and add some 1/'2 or so spacers to create an airgap between foam and OSB (and of course use longer screws). The latter is going to be pricier of course.

  3. Expert Member
    AKOS TOTH | | #3

    This has come up before on the forum. My best guess at the time is the noise is from the difference in thermal expansion rate of the OSB deck and the rigid insulation. When the roof deck heats up the foam expands much more than the OSB causing the foam to rub and make noise.

    A 10' section of foam expands about 0.4" when the sun hits the roof, the OSB deck expands about 1/10 that amount. If the roof deck is not fastened down enough and the foam is allowed to move it will make noise.

    I doubt venting will do anything to fix this issue. Getting the roof deck fastened down better is probably a good start.

    If all sections of the roof make noise, a start would be to strip the shingles in a smaller area, screw down the OSB. It usually takes much more than 48" OC and make sure to use correct fasteners not just standard construction screws:

    https://www.hunterpanels.com/docman-categories/technical-documents-roof/fastening-pattern-guides/fastening-low-slope/1370-h-shield-nb-steep-slope-wood-framing-16-or-32-oc-concrete-steel/file

    If that fixes the noise in that area (I would wait a couple of months just to be sure), you can repeat for the rest of the roof.

  4. onslow | | #4

    scofike,

    I found this thread amongst earlier GBA postings.

    https://www.greenbuildingadvisor.com/question/thermal-expansion-of-exterior-rigid-foam

    It would seem that perhaps creeping foam rubbing on the T&G might be a possible explanation. I do note that you seem to indicate one layer only of foam not two, so two layers of foam rubbing and popping answer doesn't fit. You don't say what type of foam is used or whether it is faced with plastic film. Perhaps a film faced EPS or XPS would enhance the stick and pop characteristic.

    I would be very concerned about using any roofer that thinks air would flow through the foam or that a 1/2" gap would suffice for ventilation. I am equally concerned that whoever did the OSB layer only shot screws on a 48" pattern. I am surprised the sheets haven't humped up in a visible way under the shingles. The very inadequate screw pattern may be allowing the sheets to drag against each other and make noise. I am a bit doubtful though as OSB sheets in my experience don't make much noise when slid around against each other. Still the world is a wonderous place.

    Before investing lots of thought and effort into what to do next, it would be best to know a bit more about the current roof profile from inside to out. The advice you get will be more targeted.

    What is the T&G planking held down with? Screws? Nails? How long? How many per board?

    Is there roofing paper or synthetic membrane on top of T&G and under foam? Type?

    What was/is under the metal/asphalt shingles?

    What kind of foam, what type of facings?

    How is the OSB holding up in light of all the work?

    Could you show the roofs in photos so we can spot other things best considered now?

    I was going to suggest that simply screwing down the OSB properly with 5" screws and then adding 2x4 sleepers to carry a new layer of OSB for shingles or metal roofing. That would give you some level of venting, albeit with lots more long screws to do. However, if your air control through the layers is not done properly, you could be facing a slow moisture disaster.

    I looked up Blowing Rock and find it is in the Blue Ridge Parkway. Would I be correct in thinking the cabin is blessed with a lovely view from a ridge? If so, I will reiterate my suggestion that wind uplift on the roofs is something that needs to be checked. If your roofs make noise on cloudy windy days, then the foam rubbing may be the least of your problems.

    It is not clear how large the roof areas are nor their orientation to prevailing winds. The lifting force on roofs can be quite large. Remember 747s weigh more than 300 tons and fly up just fine. (not that you have 160mph winds) Wind uplift is why I suggested checking the contact points of the rather widely spaced rafters for signs of movement. It would only take an 1/8-1/4 to generate some impressive noise. Kinda like a bear on the roof perhaps.

    The wracking forces of the wind on the structure could be causing the 1 1/2" T&G to be rubbing much like the planking on old sailing vessels. Think of the creaking sound effects used for below deck drama in numerous swashbuckling movies. The planking on your roof maybe making similar sounds. The large ceiling plane will also amplify the sound like a cello or guitar backboard. Unfortunately, boats creak because they flex in the water between waves. If your roof is creaking because of flexing (not foam rubbing) then a structural engineer would be advisable.

    I have foam on all my roof planes and metal roofing on half of them. The metal ones make a soft intermittent "dwoop" sound as they heat up in the morning, but stop once warmed. The foam layers under the PVC membrane roofs do not make noise so far. Maybe I will hear something in the future. The fact that you say the only quiet time is 4-9am is rather a bit like the wind changes along the coast. Only problem is you are way inland. My local experience of wind patterns here at 8,000 ' is a bit different and seemingly random. Observe your wind.

    Have you checked with anyone else in the area with similar construction about creaky roofs? Maybe they will scratch their heads and say no, or tell you how they solved the problem.

    1. scofike | | #5

      Roger, Akos,,
      Wow! Thank you so much for the reply and tips! You seem more knowledgeable about this stuff than many of the roofing companies I have talked to...and I have talked to 5-7 at least so far, with another one today. I drafted up a profile of the roof stackup and uploaded here. It is to scale. The only unknown is type of fastener to secure T&G to rafters, and the length. I don't know how to find out without pulling off a section of roof. I do know that this entire stackup is only secured every 48"...even though the 5.5" screws would not penetrate all the way thru the T&G and be visible inside, they opted to still only put them along the rafter line.

      Some answers to your questions:
      * There is nothing between T&G and foam as far as we can tell (no roofing paper or anything)
      * There is an underlayment (thin paper-y stuff) between shingles and OSB
      * Foam type...I dont know. It is 3.5" thick so we suspect its single slab, not two 1.75" since that seems non-standard. Its a very pale yellow/green, with a dark gray facing...almost like thin felt. Have not seen a large exposed piece of it, only a few bits that came off during re-roof last week.
      * Roofers said OSB looked good last week during the re-roof. Only replace 1-2 boards. That said, I would not know what to look for myself, so I have to trust them. Replacing OSB would add quite a bit of cost with lumber materials skyrocketing.
      * Pics of roof attached.

      The problem occurs both when heating up and cooling down (e.g. this time of year, the sun hits it around 9am and it starts waking up Rufus, as we call him), AND when windy. So yes, you are right, wind is a factor, too, however, I can live with the fact that wind would make noise, as that is occasional and easily explainable to renters (we plan to rent this out frequently). Its the former that concerns me because it is almost every day, and just about all day long. Right now it is 10am, probably 45 deg, sunny day, and its already creaking and cracking. Will get worse as it gets hotter (will get to 56 deg today). My current theory is that like Akos said above, because there is zero airgap, and this stackup is all pressed together, that the OSB is expanding like a bellows, and pressing outward into the OSB and T&G, which would explain the wood cracking sounds we hear (the sounds are much more like someone walking on wood than they are foam rubbing, FWIW, hence why I think the noise is actually from the OSB and/or T&G being pressed on).

      About the best idea I have is to have them remove all shingles, lift the OSB and put spacers (you call them sleepers, i think?) in between foam and OSB to create air gap for airflow, AND to prevent the foam from being trapped between the two wood layers and therefore giving it "room to breathe". Then we add roof vents and soffit vents. Does this sound reasonable? How much airgap is needed to allow ventilation...1-2"? Like you said, would a 2x4 do the trick? Is it really the case that foam can expand as described?

      The above "fix" will be expensive, and essentially waste the new roof we just put on, but we HAVE to fix this. Place is beautiful, and ready to rent, but can't rent it till we fix. It's that disturbing of a sound, all day.

  5. Expert Member
    AKOS TOTH | | #6

    The foam sounds like polyiso. This is not as squeaky as XPS, so it won't make much noise.

    Since you are getting noise both from sun and wind, I doubt the issue is directly thermal expansion. It sounds like you have some movement in your structure which is causing the issues.

    I have 2x6 t&g as the floor for my office and despite many attempts and hours redoing it, I can't get it not to creak. I think that modern water based clear coats tend to stick, any motion between adjacent boards cause noise.

    There is a good chance that the noise is coming from the T&G in your case as well. You can check this by getting on a tall ladder and pushing up on the boards in the ceiling. If they make noise, you found the source.

  6. scofike | | #7

    Thanks again all for the replies and ideas...its the helping me retain my sanity! My current theory based on some of the comments above is that the polyiso is in fact expanding, and pressing outward against both the OSB and the T&G...sort of like inflating a bellows. And the majority of the noise is the sound of the pressure against the T&G. The sound is definitely louder inside the house than out, and it sounds exactly like someone walking on that T&G. So is it plausible that the polyiso is expanding like that and creating the forces on the T&G? I have been trying to find more resources online that allude to foam expansion and the rate of such, but not having much luck. So still a theory. As for wind, same thing applies I would believe...either its pushing the roof down, or causing to it to try to lift (like an airplane wing). Either way that vertical movement, even slight ones, could/would create the wood-on-wood creaking of that T&G.

    FWIW - double-checking this today, but pretty certain from pics I saw of the OSB before it was re-shingled that there are only about 16 of the 5.5" screws per 4x8 OSB panel, and they are only along the rafter lines (even though they do not actually bite into the rafters...see my drawing attachment). This is...not enough, right?

  7. Expert Member
    AKOS TOTH | | #8

    A thin layer of foam expands very little in along the thickness, the small amount of expansion there will not cause issues.

    If the noise is coming from the T&G, you need to deal with it the T&G. Very unlikely that fastening down the foam or adding a vent channel will do anything.

    You can try in a small area, say a bedroom in the loft, is to drill through the side of the rafters and fasten down the T&G with pocket screws. You can fill the holes with putty afterwards to cover. If this fixes the popping, you can repeat the process for the whole house. Not easy, but might be cheaper than pulling the whole roof off to access from the top.

    The amount of fasteners per sheet of OSB depend on your local wind loading conditions, an engineer can answer what is appropriate. 16 screws doesn't feel way off the mark, the issue might be spacing between rows.

  8. onslow | | #9

    Scofike,

    I second Akos on the foam not being subject to enough expansion to cause noise. I have the fiberglass faced (the gray slightly fuzzy facing) polyiso on different parts of my house including under a roof area that get full sun for half the day. It is a commonly used form for roofs commercially. The scraps I have don't make noise rubbing them together, so I am reasonably sure that even if they did rub on the T&G, it would likely be a very muted noise.

    I am a bit puzzled/concerned by the picture you took of the cathedral ceiling portion of the interior. I don't see any indication of metal plates holding the beam elements together or onto the main ridge beam. They may concealed, but the homes I remember from back east with very similar appearance (ie: big glulams and 2x6 T&G decking) showed bolt heads that passed through steel that resided in kerfs on the ends of the rafters. The steel was a T profile first bolted to the ridge by the top of the "T" with the leg of the "T" inserted into the rafter end kerf. I also only see one support post and that is quite close to the end wall. Are there others not in the picture or is the ridge beam span open until it gets to the other end wall?

    I am planning to use similar elements in a pending build and so far, based on what little I know about using them, I am expecting to see pretty large and obvious steel brackets and plates. A bit like 1/4" thick steel joist hangers. I will of course be using a local structural engineer to make all the determinations. I just think having the roof rafter elements perched on top of the ridge beam looks dubious. My former studio had 2x12 rafters on 16" centers with a similar pitch over a 22' wide room. The engineer insisted on collar ties for every pair at 1/4 of the height down from ridge board to wall top. I was doing drywall not 2x6 T&G, which may be significant than I can properly judge.

    I also see in one photo of the exterior overhang that the roof rafter is notched like a traditional rafter. I would still suggest taking a close look at the flat notch face resting in the pocket for signs of movement. Even though you say sun warming sets the noise into motion, I don't think the insulation is the direct cause. I am still in the "creaky boat planks rubbing" frame of mind. IF the roof elements are wiggling about, there might be signs of a small dirt ring or rub mark that reveals movement.

    As for advice on how to handle the roof insulation or add-on vented roof plane, I would suggest you search the Q&A for "How do I insulate a cathedral ceiling?" You will find much to digest on the subject and answers and details much more authoritative than I can offer. Your local conditions seem to be in your favor, as the lack of an air barrier between the T&G and foam is a big no-no for colder climates. Not disturbing the moisture drying profile you have will require advice from better sources than I. Sorry this noise problem is being such a puzzler.

    FWIW, my OSB nail base panels have 18 fasteners, the only apparent difference from yours is mid field screws.

  9. scofike | | #10

    Thanks all. Just to be clear, where I believe the sound to be coming from is the flexing of the T&G. It's not the sound of foam rubbing on foam, or foam rubbing on wood...that would not be nearly as dramatic as this. This is cracking...creaking. So the question is what is making it move when it heats up. Something is moving, and something is pressing on the T&G, like someone walking upstairs in an old house. And it happens within about 30 min of sun hitting it...so there is no way the T&G itself could be expanding that quickly (thermal energy would have to move down thru the shingles, OSB and foam and heat up the 1.5" thick T&G enough to make it move...no way that could happen). I have an audio recording of it, but I doubt it can be attached here. While I like the idea of fastening the T&G as a cheap fix, you are still only attaching them at the rafters which are 4' apart, leaving lots of space for movement in between. Plus, they are likely already screwed or nailed at every joist already.

    Unless I can find definitive proof that rigid foam does indeed expand even a little in the thickness direction, I may be at a loss.

    As for the rafters, these homes were sold as kits or systems (Alta log homes), so my guess is there is some sort of hidden bracing or straps up there. Talked to the owner of Alta yesterday and he said there should be collar ties...I guess those would go over top of the rafters? I would have to go to the loft and look, and I am 3 hrs away right now. Next time I go I will look. But the sounds are not localized to just the rafter area...they happen all over the entirety of the roof, in sections. First in the part of the house that catches the sun rising, then spreading across the house as day goes on. Sounds come from down near walls and up near peak...its just all over.

    Keep the ideas coming, i truly appreciate all the info!

  10. Deleted | | #11

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  11. Deleted | | #12

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  12. Nie | | #13

    Hi Scofield, I bought a property with cathedral roof last year, I have the same problem as you described, so far I haven't gotten any solutions, you and the other people like Roger and akos really give a lot of useful ideas, meanwhile I would like to remind you that adding vents may not solve this problem because mine has ridge and soffit vents but the noises are still there, I am not sure my ventilation is enough or not, I ever thought to increase the vent space to solve this noise problem. Sorry for my poor English, and waiting for your successful solution.

  13. scofike | | #14

    Hi Nie, thanks for the reply. Just an update to anyone that cares to know...I have talked in, in total, at least ten roofing companies, several insulation manufacturers, general contractors, and even tracked down the guy who built the home in 1998! He came out and witnessed first hand the noises we hear and he said it was "normal" for log homes. If that is normal, then I don't know how people would continue to want to buy and live in these homes, so I took that to mean he just didnt want to say it was done improperly. Because the most logical explanation I have heard came recently from a GC who said that the issue is improper fastener pattern (not spaced closely enough), improper fastening process (not screwed in enough) and lack of ventilation. I know the latter is debatable, but his suggestion was to reuse the existing 3.5" polyiso foamboard but lift it up and run 1-2" strips of foam from soffit to ridge and add soffit/ridge vents. Then of course screw everything down properly this time. it's likely this house will always make some kind of noise in sun and/or wind, but that might help mitigate. I would also consider putting on metal roof rather than shingles since a lighter color roof should reflect some of the sun's energy. But right now i am going to wait till fall since it is fully booked in June and July and into Aug. Will update this thread if I ever find out a fix. Still open to suggestions or ideas, too!

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