Not the answer you were hopeing for but your builder leaves a lot to be desired. Finding leaks in new construction isn't rocket science for professionals so this should have been nipped in the bud first time around. IMO,if this type brick is prone to leaking,he should have told you BEFORE they were used on your home. Some will say it's one or more subs fault but that's not so. It's 100% builder's responsibility to choose compitent subs and stand behind their work. If you are detemined to figure this out yourself and oversee remediation,learn all the proper names of building components. Stack is that part which carry's flue gases,usually metal. If it is indeed a leaking metal stack you should get your money back. Pre-fab chimney stacks come with printed instructions. Anyone attempting to build their own should have been taught how before experimenting on other people's property. Not intending to unload,just making the point that there isn't a right and a wrong way,there is one right and more than 3 dozen wrong ways when it comes to roof sealing. If you find someone on the net to cure your problem,hire them next time because they are 10 fold smarter doing it sight unseen.

Here's useful information. Document all this so you have recourse even after warranty expires. Leaks have a nasty habit of hanging around for years and eventually requiring major reconstruction to replace rotted materials. Don't let these guys put bandaids on this until they can skip town. You may need a lawyer and good roofer instead of internet friends.

Hmmmm. Okay. I'm not sure how you interpreted from my post that I was seeking "internet friends", but thanks for your reply nonetheless. Actually, I was hoping to hear from people that may have experienced something similar and could tell me if what I've heard from our builder sounded reasonable or terribly off base. Maybe the Home Repair forum is only for professionals to come talk about the repairs they've done. My mistake.

No mistake, I think klem is just saying that it may take more than what you can get here. In any case:

I'm an amateur but it seems to me that even antique brick on a vertical wall or chimney should not be so porous as to be able to transmit enough water to cause dripping. One problem we have is that we can't see anything and don't know where the leak or the drip are occurring.

It is very possible for leaks in roofing, flashing etc. to be missed. I had a small roof leak that we just could not figure out. Turned out to be a plastic roof peak vent that had a small crack when it was installed. When it rained hard enough, water could get through and drip into the attic. I fixed it myself with a dab of clear caulk. It was missed by at least one roofing guy though - the flashing and everything looked OK.

The top of a brick chimney is horizontal so water can sit up there and run into any cracks in the brick or mortar, so watch for that.

I wish I had more for you but just make sure they are looking very closely at things.

It's the flashing. You want mechanical flashing, not roof goo either.

Thanks so much for your replies. I truly appreciate them.

Not discounting the idea, but just in case it matters, we do have mechanical flashing.

cvazcu,I didn't want to say your builder is an outright idiot. After all he might be having health or stress problems temporarly throwing off his judgment and will soon recover to make everything fine. However I believe I went more than far enough to answer your question, "If what I've heard from our builder sounded reasonable or terribly off base?" It's a mute point now anyhow,Joseph has now told you what's wrong. My hat is off to you Joseph. I have watched roofer wander around a roof hours in finding a leak and you found this one without even knowing what color the house is and scant technical information. I digress to discussion of terrapin jousting and mumblety peg.

my house had a leak when we'd have a heavy downpour. i'd go on the roof to look, nothing. into the attic and around nearby vent pipes, nothing. it was only when i could be in the attic during a storm that i could follow the trail of water. it blew in under the cap, ran 4ft from the peak of the house, down 6ft of rafter to a vent pipe attached to the rafter, through the plaster ceiling and on to the washer. drove me nuts for months. my point is you might have to get these guys looking in unlikely places or use a thermal image scope to trace the leak. a good tradesman should have one or at least borrow one.

Thanks again. I

The last comment was especially helpful. We have foam insulation on the roof, so we can't exactly tell where the water is coming from; we've only been able to tell that it drips through near the chimney and have trusted that what they've told us about the bricks being the issue is correct. So, a thermal image scope could likely pinpoint the origin of the leak (possibly assuming it is somewhere other than the chimney) without having to remove the foam insulation?

I appreciate the advice. Obviously I will be asking these questions of professionals in my area, but it is helpful to me to know what kinds of questions I should be asking.

The thermal scope was made for people with your problem. It's the latest and greatest gadget, most owners look for a reason to use it. If water is near the surface it'll show up even if it's coming from brick. Good luck

what kind of foam insulation?

I'd get an independent inspection & really
have the flashing at the chimney checked out.

waterproofing brick is a band aid.
and come on...every 5 years you have to re-do it?
builder is just waiting out his warranty.

thermal scan will show water intrusion, but if insulation
is closed cell you won't get the results you'd
expect. you'll see the wet area, but closed cell
doesn't let moisture exit.

get an inspection other than the builder of his buds.

best of luck