Our T & G roof has been making loud popping noises during expansion/contraction ever since we had to run the water lines over it. It happens in varied places. I've just found out that the wood spacer/chock blocks put between the roof and the water lines are cemented onto the roof. Could those unmoving blocks be causing the problem? We have 2" rigid insulation under the tar & gravel. What can be done to prevent this noise?
I'm not sure your water pipes would necessarily be the cause, for we've noticed similar sounds in our place. In our case, I *think* the sounds started to appear when we repainted the ceilings to cover water stains (from a rainstorm during a reroofing). My current suspici We'd also gotten the old roof ripped off and replaced with a foam roof a couple years ago, so in our case it also might be caused by the new roof or by extra movement when the roof's a couple tons lighter.
The noises you hear is the result of expasion or contraction of the tongue and groove (or also known in the building industry as T & G) roof planks. It is extremely unlikely that it is related to the plumbing that is above the roof membrane, and this condition is more common through the colder months, but will happen year-round (I remember hearing those noises throughout my childhood, and every time I had stayed home after then).
Don't be at all concerned, it is one of the quirky things about Eichlers in cooler climates.
There is another POSSIBLE explanation. Bluejays seem to have a big appetite for the insulation that is typically used to clad hot water pipes that go over the roof! Their pecking is extraordinarily loud!
FWIW, our roof used to do that when it had a tar and gravel surface. Hasn't happened since we switched to foam.
A tar and gravel roof soaks up a lot of heat, especially when it is thermally isolated from the wooden deck (tongue and groove) by insulation. There is nowhere for the heat to go, so it builds up and cooks the oils out of the tar. Everyone is right about the expansion an contraction.
If the sound is really new, please check and make sure that the pipes are not secured tightly to the blocks. The pipes themselves also change size with their own temperature changes. Since your blocks are stuck to the tar roof, it's possible to break one loose and damage your tar roof. The post about the foam roof not making noise is right on the money. When insulation is placed on the outside edge of the building envelope, the results are incredible. There is no material to soak up heat or cold and gradually radiate into the structure. The temperature of the beams and planks stays stable, eliminating the noisy movement.