Roofing/chimney side flashing details
My question is about side flashing for a brick chimney, specifically the "counter flashing" (mine is lead). My understanding is that counter flashing acts like an apron: inserted into reglet groves in brick and coming down over the step flashing--which laps with the shingles. Question: is the counter flashing supposed to lap with the shingles too? I have seen it done both ways. My old counter flashing laped with shingles--the new counter flashing just extends about 3" over shinges (no laping). Thanks!!
Around each chimney there are 3 distinct parts of the interface between the shingles and the vertical chimney. On the upslope side there is a Pan flashing, which may or may not have a cricket which diverts water to the outside (depending on the width of the chimney). This should extend under the shingles and underlayment so that water flows onto the Pan flashing naturally. On each side there are step flashings which should be integrated into each course of shingles. On the downslope side of the chimney is an Apron flashing which extends under the step flashings on each side, but is installed over the shingles. This way all of the sides allow water to flow properly, and provide the protection needed. The upper vertical leg of all of these flashings should be installed under the lead flashing that is integrated into the brick joints.
If you are specifically talking about the step flashings on either side of the chimney have been changed to a single flashing that is installed atop the shingles, then this would be an incorrect installation method.
Hope that this helped and answered your question.
---------- FOLLOW-UP ----------
QUESTION: Hi Aaron,
The step flashing is done correctly, as is the pan flashing, cricket, etc.--please see my question above. My question is about the lead counter flashing: are these pieces supposed to integrate with each course of shingles or do they come over all courses? What is best practice? Thanks again!
Sorry Steven for not understanding the original question. The best practice is for the lead to lap over the vertical leg of the other flashings and not be integrated into the shingle assembly. This will allow for movement of the building independent of the chimney, without causing any damage, and it allows the re-use of the lead flashings during a re-roof. I honestly don't ever recall seeing the lead counterflashing integrated into the shingles.
Sorry again for mis-understanding.