Flashing/Counter-flashing with Board-Batten siding

[Barry Thistlethwaite]

The builder of my attached garage installed step flashing against the board and batten siding where my new roof meets the existing house. The step flashing was flush with the battens and left a nearly 1-inch gap between the flashing and the boards. The contractor said not to worry, the roofer would install counter flashing. Instead, he hammered the step flashing to conform to the boards and battens, and put caulk along the top. I contend this will start to leak in a few years as the metal expands and contracts against the wood.

How should this be done? My understanding is that counter flashing should always go underneath siding. But I can't find anything specific to board-and-batten. What needs to happen here?

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[Chris McIntyre]

How should this be done? My understanding is that counter flashing should always go underneath siding. But I can't find anything specific to board-and-batten. What needs to happen here?

What you have is wrong.
Board and batten siding is no different than any other siding (as far as step flashing goes).
The siding should have been cut at the roof line, removed, flashed and reinstalled...or the b&b could be cut back 5" +/- and a trim board running with the rake installed with a Z flashing at the transition and the step flashing behind the trim board, this is somewhat of a shortcut so the siding does not need to be removed.

Counter flashing is a method used when flashing to a masonry wall.

[Barry Thistlethwaite]

What you have is wrong.
Board and batten siding is no different than any other siding (as far as step flashing goes).
The siding should have been cut at the roof line, removed, flashed and reinstalled...or the b&b could be cut back 5" +/- and a trim board running with the rake installed with a Z flashing at the transition and the step flashing behind the trim board, this is somewhat of a shortcut so the siding does not need to be removed.

Counter flashing is a method used when flashing to a masonry wall.

Thank you, Chris! To clarify, if they pull the siding and put step flashing behind it, you're saying no other flashing is required? Or if they install the trim board over the step flashing, Z flashing goes...where, on top of the trim board, down the face, and then under the shingles?

My contractor says he is hiring another company to come in and fix it. I want to know what to look for when they do--or what I will have to hire someone to do if he doesn't get it right.

[Chris McIntyre]

To clarify, if they pull the siding and put step flashing behind it, you're saying no other flashing is required?

Correct

Or if they install the trim board over the step flashing, Z flashing goes...where, on top of the trim board, down the face, and then under the shingles?

Z flashing goes behind the siding and terminates outside the trim board.

[Barry Thistlethwaite]

Correct



Z flashing goes behind the siding and terminates outside the trim board.

Chris, thank you so much! the diagram explains it very clearly. I appreciate the help!

[Barry Thistlethwaite]

Chris, thank you so much! the diagram explains it very clearly. I appreciate the help!

OK, they cut the battens and installed a board as you described, but the flashing on top of the board is L-flashing, not Z-flashing, and does not go under the siding. It seems to me the only thing keeping my house dry is still caulk, not flashing. Is this what you were referring to in your second option?

[Chris McIntyre]

It seems to me the only thing keeping my house dry is still caulk, not flashing.

Correct.

Is this what you were referring to in your second option?

Not even close, this is really no different than what you had the first time!
If I were using the trim board I would cut the board and batten siding, make sure the Z flashing is under the WRB. If the trim board is going to sit on the roof it should be treated and if it is treated you cannot use the aluminum trim coil.
There is more than one way to make this repair, the current builder has had two shots at it, and got it wrong twice. If you had not questioned him it would have been left this way. You may want to consider someone else (another builder or an inspector) taking a look at your addition and make sure there are no other issues.

[Mark Hagenlock]