Chimney Counterflashing Metal?

Old 10-28-05, 08:10 AM
Thread Starter
Join Date: Mar 2004
Location: Southern NJ
Posts: 128
Upvotes: 0
Received 0 Upvotes on 0 Posts
Chimney Counterflashing Metal?

Hi all,

I completed resheathing and shingling a roof except for one area, counterflashing the chimney. It seems like a very complicated part of the project. Does anyone have any recomendations? The book I have that taught me how to roof says to cut a piece of metal in the pattern of the bricks. Then bend each tab in and caulk it in the mortar line. This seems a lot easier said than done, especially since I have never been able to cut sheet metal in very straight lines. I rebuilt the brick on the chimney so I don't have old flashing to go by.

I bought a piece of sheet metal, zinc I believe, for the job but I'm not sure it its the right material. Aluminum sheet metal costs a fortune (except for the type in a roll, but that will probably be tough to keep from curving.)
Old 10-28-05, 07:13 PM
Visiting Guest
Posts: n/a
Any metal that comes in a roll would be too thin to use as counter flashing. You need some pretty thick metal to keep to the countour of the chimney. I've actually not yet installed counter flashing on a chimney although my father has done it several times. Remember to cut counterflashing for each individual shingles if possible. Each flashing up the sides should be at least 50% taller than the shingle and go about 5 inches on the roof out from the chimney. You will need a cutting saw with a masonary blade for the job. I bought a Dewalt side cut saw and a masonary blade at Home Depot a couple years ago for $100.

You should be able to find some pictures of chimneys done with counterflashing on the net for an illustration of how to do it properly. For the top and bottom section I'd go to the second motar line and make your cut. Make sure you have a good five inches of metal going over the top of the shingles on the bottom and it wouldn't hurt to have a foot of metal under the shingles on the top. It wouldn't hurt to pick up some roof tar and clear silicone either!

The two most common areas for homes to leak is around skylights and chimneys.
Old 11-07-05, 07:01 AM
Join Date: Jan 2004
Location: Park City, UT
Posts: 275
Upvotes: 0
Received 0 Upvotes on 0 Posts
I use regular step flashings and cut the tops to match the slope of the roof. Finish with a mechanically fastened "termination bar" along the tops of the step flashings and seal with sealant.

Thread Tools
Search this Thread
Ask a Question
Question Title:
Your question will be posted in: