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Old 03-17-2011, 06:51 PM   #1
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Flat roof noise when sun hits it


Last year we purchased a 2500 sfq single story house with a flat roof. While we were in escrow, I have noticed that the roof was making extremely loud popping noise throughout entire house which concerned me and I was able to get some credit from seller which helped me in re-roofing.

Upon removing old 2 layers of roof my roofer noticed that they sandwiched the room by putting 2 x 2" inch Rigid insulation on top of our original rood (which is 1" by) then they put some plywood on top and then the roofing material. Problem was that instead of using screws to attach plywood to the 1" by they used nails! And not even long once, so nail was only like 1/4 inch in the 1" by. So seeing this my roofer told me that this is a problem why roof was making noise and told me that we don't really need a plywood on top of 2 layers of rigid insulation and that he had done this before without plywood. So what he did is used long screws to attach insulation to the roof after removing plywood and them put the roofing material back.

After re-roofing everything seemed to be nice and quiet until last few months. I started hearing this noise again. Of course it is nothing compared to what is was before and is probably 90% less. However, some days when we have a big difference in temperatures during the day I hear popping noises again.

I did a lot of research and can't really find anyone with the same issue. I'm not sure what exactly could be making noise there?
I was thinking of applying this white reflective coating on top of our roof hoping that it will reduce the heat and will help the problem but I know that this is a 50/50 chance and I may still have this issue after I do that.

Any ideas are appreciated! I feel really desperate as we totally remodeled the house and put a new roof but this noise is really distracting us..

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Old 03-17-2011, 06:55 PM   #2
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Flat roof noise when sun hits it


I found this article online. I'm not sure this is really my problem:

http://ezinearticles.com/?Flat-Roof-...st?&id=4138556

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Old 03-18-2011, 07:21 AM   #3
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Flat roof noise when sun hits it


What kind of roofing material was used? Can you describe the roof system from the rafers up to the surface? I've heard roofs make noise when two different materials are used that inadvertantly bond together, such as old tar paper bonding insulation board to a roof deck. When one material expands, it creates a "POP" as it breaks the bond.
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Old 03-18-2011, 10:42 AM   #4
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Flat roof noise when sun hits it


My deck pops like crazy in the cold whether, it's the tempurature changes expanding and contracting the wood. It's normal, though how much would it cost to throw a gable on that house?
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Old 03-18-2011, 01:06 PM   #5
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Flat roof noise when sun hits it


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My deck pops like crazy in the cold whether, it's the tempurature changes expanding and contracting the wood. It's normal, though how much would it cost to throw a gable on that house?
I have no idea, but I'm assuming a lot. Plus our roof is brand new.... I would probably be more cost effective to just raise the roof and add some space for ventilation, but again I have to tare down the new roof...

I wonder how much those reflective white coatings can reduce the heat on this flat roof? Some reviews say that they reflect 80% of the heat and probably reduce the temps of this roof by 50% so if that happens then maybe it may solve my case. Who knows... I was hoping that there is someone on this board that faced with this situation before. I know most likely our house wouldn't have this issue somewhere down the hill, where temps don't changes as drastically or if we have some kind of shade tree around us.
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Old 03-18-2011, 02:59 PM   #6
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Flat roof noise when sun hits it


What I'm also not understand is what really makes noise. I suspect that it is not the actual wood and is a roofing material. Because I doubt that after 2 layers of 2" Rigid insulation our 1" by wood is getting that hot or that cold...
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Old 03-18-2011, 03:50 PM   #7
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Flat roof noise when sun hits it


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I have no idea, but I'm assuming a lot. Plus our roof is brand new.... I would probably be more cost effective to just raise the roof and add some space for ventilation, but again I have to tare down the new roof...

I wonder how much those reflective white coatings can reduce the heat on this flat roof? Some reviews say that they reflect 80% of the heat and probably reduce the temps of this roof by 50% so if that happens then maybe it may solve my case. Who knows... I was hoping that there is someone on this board that faced with this situation before. I know most likely our house wouldn't have this issue somewhere down the hill, where temps don't changes as drastically or if we have some kind of shade tree around us.

There was no ventalation space? That's a huge issue. You are baking and rotting that wood all at once.

roof trusses and sheeting can't be that bad price wise, the venting it would be easier.
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Old 03-18-2011, 06:13 PM   #8
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There was no ventalation space? That's a huge issue. You are baking and rotting that wood all at once.

roof trusses and sheeting can't be that bad price wise, the venting it would be easier.
We live in SoCal andI have never seen a house with a vented flat roof here for some reason. I have asked neighbors with similar construction and flat roof and none of them seem to have venting and also do not have this noise. The only difference is that they do not have 2 x 2" Rigid insulation. But I thought this should only only, no?
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Old 03-19-2011, 07:38 AM   #9
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Flat roof noise when sun hits it


It still goes back to roof type and how it was installed. Were slip sheets used under the insulation or was it bonded to the deck? Mechanically attached or chemically? Without knowing what and how, it's just a guess. Flat roofs are rarely vented since the insulation is part of the system and if properly designed there is no place for moisture to condense.
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Old 03-19-2011, 07:43 PM   #10
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It still goes back to roof type and how it was installed. Were slip sheets used under the insulation or was it bonded to the deck? Mechanically attached or chemically? Without knowing what and how, it's just a guess. Flat roofs are rarely vented since the insulation is part of the system and if properly designed there is no place for moisture to condense.
Insulation was laid directly onto 1" by, without slip sheets, and it was not glue, roofer used 2 1/2" screws with caps to hold it in place.

So not having slip sheets could be a problem? Can you please explain why? I'm not not understanding how our roof sheeting can heat up when it is seating behind almost R25 insulation? Should it actually make it better?

Also, maybe I should also mention what type of roof/ceiling construction we have. We have an open beam ceiling with HUGE beams (about 11" x 5") that are about 4ft apart. And roof sheeting (1" by) is laid right on top. So at some point I was thinking maybe issues is where roof sheeting is attached to our beams? Maybe I needed to re-screw them?
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Old 03-21-2011, 09:54 AM   #11
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Flat roof noise when sun hits it


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We live in SoCal andI have never seen a house with a vented flat roof here for some reason. I have asked neighbors with similar construction and flat roof and none of them seem to have venting and also do not have this noise. The only difference is that they do not have 2 x 2" Rigid insulation. But I thought this should only only, no?

They pink insulation foam board they used, should have been cut in strips and placed only under the 2x4 or 2x2 (what ever they used). This allows air to vent between the framing. Imagine a virtival lines running the length of your house. The insulation should have been in strips underneath those vertical lines. This allows channels of air to flow.

If your neighbors aren't general contractors they probably aren't the best source of information on how their roof was built.

But here is an unvented flat roof:
  • The thermal resistance (thickness) of the rigid insulation is climate dependent and moisture load dependent.
  • The colder the climate the higher the thermal resistance required for the rigid insulation.
  • The higher the interior moisture load the higher the thermal resistance required for the rigid insulation.
  • Membrane roofs and shingle roofs can experience night sky cooling that can depress roof deck temperatures significantly below ambient air temperatures. When membrane roofs and asphalt shingles are used it is typically necessary install rigid insulation above the roof deck or install air impermeable insulation below the roof deck.

Last edited by pjordan4477; 03-21-2011 at 10:04 AM.
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Old 03-21-2011, 09:28 PM   #12
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Flat roof noise when sun hits it


I clearly understand what you mean.. What would you suggest doing now? Unfortunately I can't tear apart a brand new roof and redo it all.

What I have noticed is that cold weather is not an issue... We could have several days of rain or just cold weather and as long as sun doesn't come out or even if it's hiding behind a small cloud we don't have the popping noise. So this is telling me maybe if I try to keep this roofing material cooler, then it might reduce the noise?
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Old 03-22-2011, 12:43 PM   #13
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Flat roof noise when sun hits it


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I clearly understand what you mean.. What would you suggest doing now? Unfortunately I can't tear apart a brand new roof and redo it all.

What I have noticed is that cold weather is not an issue... We could have several days of rain or just cold weather and as long as sun doesn't come out or even if it's hiding behind a small cloud we don't have the popping noise. So this is telling me maybe if I try to keep this roofing material cooler, then it might reduce the noise?
Well, there isn't much you can do if you're not willing to have it done (or re-done) correctly. I will tell you this, it won't last long in this condition so you'll get an opportunity to have it replaced. I hope it doesn't cause extra damage.
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Old 03-22-2011, 03:09 PM   #14
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Flat roof noise when sun hits it


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Well, there isn't much you can do if you're not willing to have it done (or re-done) correctly. I will tell you this, it won't last long in this condition so you'll get an opportunity to have it replaced. I hope it doesn't cause extra damage.
How are you assuming that it wont last long? I have talked to 10 different roofing companies in our area and all of them told me that flat roof ventilation is not needed here and that they all do install rigid insulation right on top of the 1" by all the time and that does not really cook the roof. Maybe I'm not explaining it properly here but we have a 1" by 6" and then 2 layers of 2" rigid insulation and then roofing material. On the inside of the house we have R19 fiberglass and then drywall (this was actually installed later), before 1" by 6" were exposed from inside.
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Old 03-29-2011, 03:24 PM   #15
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How are you assuming that it wont last long? I have talked to 10 different roofing companies in our area and all of them told me that flat roof ventilation is not needed here and that they all do install rigid insulation right on top of the 1" by all the time and that does not really cook the roof. Maybe I'm not explaining it properly here but we have a 1" by 6" and then 2 layers of 2" rigid insulation and then roofing material. On the inside of the house we have R19 fiberglass and then drywall (this was actually installed later), before 1" by 6" were exposed from inside.
If the wood is popping, then it's expanding from the heat...which leads me to believe it was not done correctly. If it's not done correctly, it won't last long.

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