Expert: Bart Ogden - 10/11/2006

Question
Bart, I can't find this problem discussed anywhere. If you can provide some insight, thanks.

I have a double-wall metal chimney inside a hollow stucco 2 story box... typical, generic, tract-housing construction.  

One day I cut a hole in the back wall of my upstairs closet hoping to find a hidden attic space. Instead, I had cut into the back of the hollow chimney stucco shaft.  

Here is the problem. It happened to be raining, and I was surprised to see water running down the outside of the round metal chimney. After removing some metal fire-blocking, I could see all the way to the bottom; below and to the side of the actual firebox.  It was/is plywood and it was all wet. I can't tell if it is rotted or not.

I had a roofer come out and he put more sealant on top.

That was two years ago. It still leaks when it rains. I am having the house painted now and have scaffolding installed.

Today I climbed to the top of the scaffolding (35 feet!) and the chimney top looks good. A seamless metal rectangle slopes to the outside edges and folds over the stucco.

The round stack in the center is fused to the metal rectangle and then it has a metal flashing ring about 2 inches above the metal rectangle. The ring's top edge is caulked all the way around the stack with no cracks or separations.

Then the stack has a band of spark-arrestor screen and then a cap on top.

Through the screen, I can see the center stainless steel core of the double-walled metal chimney. I can't see it, but I presume the stack is screwed right onto the outer galvanized metal layer. (Or, is there a gap between the outer wall and the stack?)

Could rain be blowing in through the screen and then hitting the top edge of the outer wall?

HERE IS THE QUESTION: I wonder if there should be another ring of flashing or sealant on the inside of the screen against the outer wall of the chimney so that any rain that hits the outer wall will shed onto the metal rectangle.  

I couldn't see up under the 2 inch rise before the metal flashing ring. But it would make sense that the rain should be shedding onto that.

I hate the thought of taking the whole assembly off of the chimney 35 feet up. Are there any online diagrams or schematics of what the installation should look like?

Thanks for any help.

Jim

Answer
Hi Jim,

You need to take the top assembly off and put water on the chimney so you can see if it's coming through the sides.

If it's not there, it's in the top.

There should be a chase cap with a 2" collar (soldered in place)topped by a storm collar and a cap with an integral rain bonnet to keep the rain out of any inner air spaces between the liners.

Thanks for using AllExperts.Com and good luck with your project.

Sincerely,
A. Bart Ogden, President
Home Safe Hearth & Chimney
Wichita, KS
Voice: 316-265-9828
Fax: 316-265-9890
www.homesafeks.com