Expert: Mark Sundberg - 8/5/2009

Question
Hi,

I am hoping you can help me.  We moved into our one-story home about 3 years ago.  This home was built in 1999.  

We noticed that this home makes noises throughout the day.  It's not a constant noise, but it happens at any time of the day.  It sounds like it's coming from above the ceiling.  The sound can be described as someone using a nail gun.  It's a quick popping sound and then we'll hear it again later on.  

Can you please shed some light as to what this sound could be?

Thank you so much for your help with this!!


Answer
Hi Leilah,

Sounds like the roof is heating up and there is shifting between the sheathing and the framing. This can happen in areas with high temperature swings between night and day where the roof sheathing hasn't been fully adhered to the framing. During the night, the roof sheathing cools off, so does the roof framing. With the morning comes the sun and the roof starts heating up. The framing will do so eventually, but it follows the sheathing by a while, often a couple of hours and a few degrees. Come the evening, the whole thing goes into a cooling cycle and then starts all over again. The roof sheathing goes through a greater range of temperatures but is more stable, due to the layers going different directions and/or the epoxy matrix the wood fibers are embedded in so it expands/contracts less per degree, but there are more degrees. The framing is likely to be some sort of dimension lumber, perhaps in a truss configuration, and it expands/contracts in one direction, lengthwise, which is often more than the roof sheathing but it goes through a lesser range of temperatures.

So, on one hand, you have the roof sheathing trying to get bigger and smaller in both directions while the framing is doing so only in one direction. Without an effective glue bone, the nails slip and when they do, they make a popping noise such as you describe. It could be just one rogue nail that's not quite properly seated or it could be a bunch of them. Hard to say without being there.

Unfortunately, there's not a lot you can do that's not rather expensive. What needs to be done is the roofing taken off, the sheathing removed and then reinstalled with effective adhesives and then the roofing reinstalled. That would be very expensive. If it's a single nail, it may be you could remove just a small portion of the roofing and add two or more nails on either side of the offending nail and maybe even remove it.