I think I have a problem with a fairly new chimney

I am far from an expert, but it doesn't look like smoke is leaking to me. It looks like they didn't put enough mortar in at first and after the original stuff was partially dry they added more. Which would explain the different color. Is there any blackening of the wood directly above that point?

No steel liner? Although it does look like a patch I agree with you shouldn't assume anything. Before I went with the insert I had smoke coming out between the mortar of the brick above the lentil and from under the wooden mantle. The installer left a 1" or more gap between the front of the damper assembly and the brick. The mortar was blackened, dry and crumbly. Without a fix it would have gotten worse and worse.

Any way you can inspect it for a gap between the clay tiles? Could burn an intentionally smoky fire, maybe even some newspaper and go look at it. With the lights out and a flashlight you could probably see any smoke. If you have a IR thermo you could check for hot spots. Short of that get a pro.

A liner would definitely be a fix. I too would suspect that there is a gap of some sort on the inside of the chimney. If it truly is just that one area, and the inside of the chimney is fine, then just take a grout knife to it and get out all that old mortar and put in new.

A ss liner is safer all the way around regardless

Are you saying you can smell/see smoke coming out of that block joint?

If it the block is lined with clay tiles,,,then that would mean the tiles are leaking also, right?

Also, if you have decent draft, shouldn't the smoke be carried right up and out regardless?

I would be adding a SS liner to that chimney ASAP.

What is the inner dimension of the clay tiles?

Well if you just had it built call the mason who did it. The stove will probably be happier w/ a liner anyway but if there's a gap you want to know what the story is (i.e. how big and where).

honestly I would line it. Better safe then sorry. I would line it with SS even if it was 100% good just for the safety factor.

How much room do you have? enought to put a 6" liner?

Those block are fairly hefty. Chances are good your mason squashed the joint laying that block then wedged it back up into position leaving a mostly empty joint inside. You can see the cracking in the joint which is indicative of what I call a dead joint.
The large difference in color is strange. If he fixed it right away there shouldn't be that much difference. Almost looks like he used straight Portland cement but doing so doesn't make much sense.

This condensation you refer too. Let me guess. Your burning scrap lumber collected from the site.
I once had me a customer who shortly after I finished a little stack chimney on his house marched out into a swamp, found a large living beech tree laying on its side and chopped off a wheelbarrow full of limbs everyday and burnt them.
He blamed me, the mason because black water was pouring out of his clean out door and running across his basement floor. Kid you not there was eight inches of black water in the bottom of his chimney and overflowing out the door.

I'm thinking your condensation is from burning some wet wood that's creating watery creosote and it found a pocket in that dead empty joint and that is causing the strange discoloration and smell.

I'd recommend that joint be cut out deep with a largish diamond blade and repointed. Cut two opposite sides and point, cut the next two and point. Stucco/parge around the whole joint and call it done. And if your not doing the work watch it be done so some fly by nighter doesn't just score that dead joint and pack another touch on top.
There may be a hole between the flues. That's not uncommon. Shouldn't happen but it does. Some masons lay them dry to begin with, shouldn't but I've seen it done. Most chimneys with some good age on them have no mortar left in those flue joints anyway. It's not optimal but it's not also not the most dangerous thing in the world. The joints on the block work are really your main line of defense against fire.

If that's not good enough you'll have to line it.


As an aside, once it starts getting below twenty degrees in an unheated house and you start a rapid blaze in a chimney. You can split that thing wide open by the sudden heat differential. Go slow when everything is really cold.