Oops. I believe I have done my step flashing wrong. :-(

OK guys, please don’t laugh. I’m in the middle of re-shingling my house. Granted, I’m not an expert at this. But I’m researching every thing and trying to do it all properly. I’m doing the roof in sections. So far, my job has included ripping off two layers of shingles, replacing rotten roof decking, applying new felt and shingles along with step flashing and apron flashing.

When I did my step flashing up the sides of our dormer, I was careful to layer the step flashing with the shingles and also to make sure that I had at least 2" of overlap on the flashing. However, I think there is one crucial requirement that I missed. When I put down a piece of step flashing on top of a shingle, it seems necessary that the bottom edge of the step flashing should be just below the tar strip. Correct?

When I did my layering, I did not ensure this. Therefore, I have some many areas where I have two inches of overlap, but the bottom edge of the flashing is several inches above the tar strip. In hindsight, it seems pretty clear that this will enable the shingles to seal in front of the flashing and causing any water that gets in to get trapped. Am I correct in my thinking?


Pics would help.
Your step flashing should be large enough to cover the portion of the shingle that doesn’t show. IE 7 inches on a standard size shingle and 7 5/8" on a metric shingle. Usually they come in 4x4x8 pieces. If you have a larger shingle than this you must bend your own.
As long as you have lapped the flashing pieces 2" and woven them between the shingles it is likely you won’t have a problem. I would like to see what you did.
What is the pitch of the roof?

Tar lines are place in a lot of different places depending on the type of shingle and the brand that you are using. Your step flashing should be layed in where the bottom of the next course of shingle is going as this will give you the best coverage. Making sure that the step does not hang below your next course but covers the row underneath as shangle_nailer said.

Hi guys, thanks for the replies. The pitch of my roof is 7/12. As for the picture – please bear with me. It is hard for me to take a picture right now, as I haven’t yet ripped off the shingles to redo the step flashing. And it has been raining here today. So, I probably wont’ be able to until Friday. However, I’m attaching two pictures. The first is a drawing I found in a book that shows what seems to make logical sense to me – that of the flashing resting on top of the tar strip:

The second is an horrendous computer drawing that seeks to mimic the picture above, but shows how my step flashing was done:

Because of where the previous row of shingles were, in relation to the where the dormer started, when I started step flashing, the flashing was shifted up, if you will. I still have two inches of overlap. However, the tar strip is “below” the end of each piece of flashing. I hope this picture explains what I believe my problem is. It seems to me that water will get trapped in my layout.


there are gaps in the tar strip that would let trapped moisture out so as long as you aren’t using an OC duration shingle or a shingle with a solid tar strip you should be good :wink:

Oh, thank you! In my thinking about my step flashing, I had completely neglected to remember that the tar strip was not continuous. My shingles are Castlebrook 35 year shingles purchased from Menards – not solid.

Slowly starting to feel less sick. :slight_smile:


yeah your fine bud! now the question is, where did you place your nail to fasten the step shingle to the deck? is it high or low? if its low i would go back and hand seal them with caulking. if they are high like under the above step shingle then your good to go!

Fortunately, I did nail them up high. :slight_smile:


good to go and a nice how to pic there Bryan.

then quit worrying! hahaha

Bryanwalton…The pic on the book shows a bad nailing procedure when fastening to the flashing.

When you install your next step flashing…place the nails high and make sure the nail goes through the flashing and shingle underneath it. An inch higher…you will nail through the flashing and the deck…NOT GOOD

Place your next shingle over that flaShing… then place a new flashing. Following these steps, you will see that those nails get completely covered and won’t see a drop of rain.

Nail placement in the book can get plenty wet…water will move sideways at the key way and wall transition.

I agree with roofer gee. I dont place nails directly through my step I lay my shingle over the step flashing then then nail through the step and the shingle. Then the next piece of step covers the nail.