We live in a brand new 3story house. In the master bedroom (which shares a wall with the master bath) I have been hearing a constant dripping sound (every 30 seconds) or so. There is no visible moisture on the walls, ceiling and it is not a knocking sound.. distinct drip. I've heard it for months...
Could we have a leak in the walls without visible water damage? The house is less than a year old.
The noise is not only driving me crazy but it is scaring me! Our builder warranty runs out in 3weeks.
I don't know what to do.

I can't imagine leaking for months and no sign of water. Could be a drip from a vent pipe here it makes a turn. Water condenses in the pipe and drips off a piece of pipe or possibly a glue blob. I offer this as a suggestion since there is possibly a vent pipe in the common wall.

Well, whatever the cause is - you should definitely alert your builder and have him fix it.
I don't know how expensive the house is, but I am sure you did not specif to have an annoying dripping sound in the walls when you contracted to have the house build according to certain specifications.
The builder will make all kinds of lousy "explanations" and tell you why he should not tend to it.
Bottom line is - he has to make the noise go away (at his cost) even if he has to tear down all the walls and reinstall the plumbing from scratch.

Hey RC

I'm afraid it is you that needs the reality check here as you have NO CLUE what you are talking about... ;)

Buildings, especially new buildings can expand/contract and settle over time, so there is no reason to have the builder fix anything or come up with any, "kinds of lousy explanations"!

Mark

Well, you are obviously the expert (at least per your handle) - however, you are not up to date.
There are NO excuses for a plumber to use old techniques that makes noise when temperatures shift.
There are plenty of ways to avoid this and any skilled plumber/builder would be aware of them and should use them in refurbished or newly built houses.
Having renovated seven houses, I actually do know what I am talking about and in two of the houses this was a problem - the builders fixed it after I explained to them how.
One issue was behind a wall, the other had to remove a ceiling, but nothing major, just a couple of weeks of extra work due to sloppy plumbers not insulating pipes, checking angles and using the latest materials.

This is just like an electrician stating he cannot fix the twisted light switches, because he already made the hole in the wall... change the wall then!

Hold the builders and worker responsible - always!

Seven whole houses huh? LOL! Hey, I hate to be the internet police, but I think your advice is off a bit here...

Reread the original post RC...you just made a mountain out of something that isn't there (seeing how this thread is from back in April). We get complaints like this all the time...simple expansion and contraction of the house settling. You are WAY OFF BASE with your answer and your over the top NEGATIVE explanation(s).

I will agree that at times things happen as you presented...no doubt, but here, it is not the case as you suggested is all, OK?