Ceiling near chimney problem

[BarryJ]

My chimney goes up thru the middle of my ranch house. I have been having flaking and a yellow stain on the ceiling, right where it joins the chimney. I thought it was the warm air going thru a air leak and causing condensation with the cold air of the chimney. It was better in the summer, but it is starting to get cold again, and is starting to flake again. Last spring I went up in the attic and sealed the metal flashing against the chimney, but the problem comes back.
Now up in the chimney, The rafters go around the chimney, but has a 1-11/2 inch space around the chimney, ..some (half around) has the metal flashing against the chimney, that I sealed. But, the other section, just goes all the way to the cellar.
Since the rafters (wood) does not go all the way around, I think the air is still mixing and causing condensation.
Can I box in the chimney with 2x4s or 2x6s and throw insulation inside, and then seal that up?? Or will that cause more problems.
I am getting frustrated.
I will try to post pics.
Thanks, Barry

View attachment inside ceiling.jpg

View attachment chimney sealed.jpg

View attachment Chimney sealed 2.jpg

 

[oldognewtrick]

You have thre possible scenarios going on. You have aleak from the crown of the chimney where the flue exits or you have a flashing issue around the base of the chimney either step flashing or counter flashing improperly installed or you have water leaching through the mortar joints of the brick. Caulking from the inside should never be done. You are not preventing water intrusion, you are trapping water. Insulating the chimney is a waste of money and time. Make sure you have a proper vent system to get rid of moisture and address the water issue from the source. That will be outside.

 

[havasu]

Yeah, I'd like to see pics of the flashing on the roof. I'm guessing that is where your problem originates.

 

[BarryJ]

There must have been a miss understanding somewhere, where I talk about sealing the chimney, it was on the chimney inside the attic, where it meets the floor, not on the roof, it was with "fireblock". The problem did not get worse during the summer when it was raining out, so a leak was not even on my radar. It got worse when the temp dropped outside and inside the attic. There was unfaced insulation wrapped around the chimney in the attic, which I since took off, to see id it got better. It seems to be getting worse.
Could it be a leak, ,probably, but becasue it happens only in winter, I figured warm air from ceiling mixing with cold air in attic equaling condensation of some sort. I will take a picture of the outside of chimney. If I need chimney work, would I call a mason or chimney cleaner?
Thanks
Barry

 

[oldognewtrick]

If it's a condensation issue, you should see moisture collecting on the bottom of the roof sheeting. I've never encountered condensation solely on the chimney. If you see white chalking on the brick, that is effervescence and it's the result of water leaching through and leaving salt deposits.