# Flat roof noise when sun hits it



## mtrx (Mar 9, 2010)

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

http://ezinearticles.com/?Flat-Roof-Insulation---Is-it-Really-Worth-the-Cost?&id=4138556


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## Maintenance 6 (Feb 26, 2008)

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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## pjordan4477 (Mar 15, 2011)

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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## mtrx (Mar 9, 2010)

pjordan4477 said:


> 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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## mtrx (Mar 9, 2010)

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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## pjordan4477 (Mar 15, 2011)

mtrx said:


> 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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## mtrx (Mar 9, 2010)

pjordan4477 said:


> 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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## Maintenance 6 (Feb 26, 2008)

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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## mtrx (Mar 9, 2010)

Maintenance 6 said:


> 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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## pjordan4477 (Mar 15, 2011)

mtrx said:


> 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.


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## mtrx (Mar 9, 2010)

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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## pjordan4477 (Mar 15, 2011)

mtrx said:


> 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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## mtrx (Mar 9, 2010)

pjordan4477 said:


> 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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## pjordan4477 (Mar 15, 2011)

mtrx said:


> 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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## mtrx (Mar 9, 2010)

pjordan4477 said:


> 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.


I was thinking that I was more of a nails popping noise. Where obviously nails will get warmer faster and will expand faster and will make popping noise. Is that possible? Because noise that I hear is not the wood to wood noise, it's more of a noise that you hear when trying to remove nail from the wood.


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## SteelToes (Oct 5, 2010)

How thick is the plywood that's over the joists?


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## mtrx (Mar 9, 2010)

SteelToes said:


> How thick is the plywood that's over the joists?


There is no plywood over the joists. Joins themselves are pretty thick. They are 1" x 6".

So here is how I have it (from top to bottom):

roofing material
black roofing material
5" screws with caps holding insulation
2" rigid insulation
another 2" rigid insulation
1" x 6" roof sheeting


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## SteelToes (Oct 5, 2010)

1x6? or 1x6 TG?
That's not enough meat.
That should of been 3/4" TG plywood.
What you have down its most likely pine 1x6.
Pine splits when nailed or screwed down and that's what you hearing.


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## SteelToes (Oct 5, 2010)

And by the way those screws with the caps are the worst thing.
Don't you be walking to much on that roof because once you step down on the roof you are compressing insulation and driving those nail heads straight thru the membrane.

I've replaced a fairly new roof on a fast food restaurant just because of that , workers kept going up on the roof to empty up the grease bucket from the kitchen exhaust walking on the pretty much same setup what you have.


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## mtrx (Mar 9, 2010)

Here are actual pictures on 1" x 6" from the bottom and the beams. Second picture was taken when the old roof was taken apart. It had pretty much the same setup but had extra plywood with short nails and the 2"x4" that you see was installed only around the overhand in order to save on insulation, but my roofer insisted to remove it and add insulation in order to have a propel level.


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## dog3 (Jun 15, 2011)

*Roof rigid insulation noise*

Did you ever find a solution. I live in Southern California and have a flat roof. The noise started 3 years after the rigid insulation was installed. it is very loud. i am at my wits end. nobody seems to know what is the problem. My roof structure is the same as yours. I never had problems before the insulation was installed. It occurs when the temperature changes, which is 2 times a day.


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## Nf2100 (Sep 19, 2019)

Hi - I’m having the same issue. Mine is in SoCal as well 1960s flat roof - post and beam - no attic or cavity. The ceiling is tongue and groove wood. Please let me know! I don’t trust roofers to approach this correctly. Thank you!


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## carpdad (Oct 11, 2010)

Looks like the OP was guessing but no resolution was posted.
Popping noise is usually the wood movement. The original 1x6 boards were probably hitting each other because the nails had become loose from the frame. All nails eventually become loose.
The original roofer who removed the top ply layer was guessing but I think wrong, but helped with the problem by removing the forces adding to the movements.
Foam insulation does not stop the heat transfer so the heat reaching the lumber would have been slower but happened none the less.
You can solve your problem if you are reroofing by exposing the underlayments and renailing them new although screws would last longer. Foam insulation shouldn't be making noises.


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