The thumping happens only when it rains. Its not the pipes expanding entirely different sound rain or shine, its not the flue(new one installed), the chimney is wood on the outside,the cap has been caulked a couple of times with no difference. It sounds like metal being hit by drops of water and it happens every 8-10 seconds steadily whenever it rains. You can only hear it in the master bedroom, not downstairs or the upstair bathroom. How can we locate it? without ripping up the entire wall?
2012-11-26T15:17:13Z
No we have had mice and we even had a rat! Its steady not a rumbling like rodents. No we dont' have any trees around for squirrels. Its a steady thumping I can almost cost the seconds inbetween its very hard to sleep with that going on we tried sound machines and a fan to drown it out but its very loud!
2012-11-26T15:19:28Z
I meant count I am ready to tear out that section of wall and search it!
?2012-11-26T15:25:53Z
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Get a new chase cover and storm collar... most likely that noise is rain coming in around the flue and dripping on to the fire stop (a metal plate surrounding the flue at each floor level... ask the chimney tech installing the chase cover to visually inspect the interior of the chase for wood rot... chase covers are custom made and expensive but have a lifetime warranty unless you find someone to install a galvanized one but that will leak again... we used to charge approximately $450 for each flue unless the chase is abnormally large... caulking wont help anything if there's corrosion ... I've seen chase covers completely eaten through with holes the size of basketballs
I think you'd be wasting time and money tearing out the wall to look for something that's probably inside the flue. The whole flue is probably standing freely like a big organ tube ready to vibrate and resonate every drip. Chances are that the water is either hitting a bend in the flue or the damper. It all comes down to preventing the water from getting in. Get up there with a garden hose that has a good nozzle (control) so you can make it rain and watch how the water is getting in. Then someone can listen for the noise as well to confirm it to be the cause. Perhaps there is bad flashing or a leaky boot and the water is dripping onto something else in the attic or down a chase wall... still a few possibilities, but it all comes down to water infiltration. You need a controlled experiment to identify the cause if it can't readily be seen (and you don't want to wait for the next rain storm and stand onto of a ladder in it...) Anyways, it should become obvious under those conditions (garden hose). If the leak was outside of the pipe then consider the potential for moisture damage/mold growth inside the home where it went. If the drip was inside the flue then it's probably of no concern.
From your description, it sounds like water is getting in through the cap. The cap should cover the wood completely and run down the wood at least 2 inches or have a flashing to do this which sits under the cap.
Hire a reputable Heating contractor check it and fix or replace the cap.
If the rain is a driving rain, water could be forced under the cap and dripping down inside the chimney.