How Much Should it Cost to Replace Flashing Around Chimney Small Cape

Updated November 25, 2020
beige home with single driveway
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Question by supernero: how much should it cost to replace flashing around chimney, small cape

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Answered by ExteriorUpgrader: If it is done when your roof is being replaced, I would figure it should be included when the bid is done probably $150-300 included in price.

If it is being done as single service, my guess is you will pay double that because the person doing the job, still needs to set up and clean up.

Answered by LCD: It depends a lot on what type of flashing you have, and type of chimney - the $150-300 ExteriorUpgrader gave you might suffice for a riveted flashing on a metal "fake" chimney or step flashing on mortared type of chimney.

I would expect more like $250-400 range if this is base flashing where the entire flashing lies under the shingles except for exposure on the downhill side sosomeshingles usually have to be removed; or step flashing fully embedded in the chimney (as opposed to fastened with a caulked batten strip) because it has to be chipped or abrasive-wheel ground out of the chimney, then new individual pieces (perhaps as many as 20-40) of step flashing installed - plus replacing the uphill and downhill pans. Oh - BTW - brick or concrete block chimney flashing should be installed in the joints, NOT cut into the bricks, even though running along the chimney with an abrasive blade in a skil saw to form a single slot paralleling the roof is much faster than the correct method of individually forming step flashing anchored in mortar joints, run down the chimney, then bent at a compound angle to form the step.

Of course, if using copper flashing, cost can go up a hundred or two depending on chimney size - the above numbers assume galvanized flashing. Ditto if you are talking very large or multi-flue chimney.

You can also find links to a few more posts of similar questions with responses to this question right below these answers.

One thing I recommend if not step-flashing (which is short in the uphill-downhill direction and daylights at the bottom of each piece so not as much of a problem) - if it is single-piece flashing all along the sides of the chimney and lying under the shingles along that length, there is nothing to prevent the water from running sideways off the flashing and in under the shingles, especially as this type installation tends to be high at the chimney side and lower at the other side, promoting sheet flow diagonally on the flashing rather than striaght down-hill. So I do one thing always, then one of two other things (depending on existing shingle type and flexibility and access) on all flat-surface (as opposed to inward-sloped valley) flashing. First is to run a thick bead of asphaltic roofing mastic down the flashing (either stepped or single-piece type) just under the edge of the shingles, to keep at least the majority of the water on the exposed flashing rather than letting it get under the shingles.

Secondly, one of two things: My preference is to put an upward edge fold all along the edge of the flashing away from the chimney, so the edge is folded back on top of itself relatively flat but not rolled down totally flat - this gives a little raised lip or cupped-edge at that side to keep the runoff on the flashing rather than letting it run off the side of the flashing under the shingles. The other alternative is to run a thick bead of roofing mastic down the flashing edge as far under the shingles as you can reach to serve as a levee the same way. Because of the sloped installation of shingles on the roof (they do not lie flat on the roof surface, so there are gaps above the uphill edges) it will probably not actually bond to the underside of the shingles everywhere, but if thick enough might - and will act as a barrier to lateral water movement regardless.

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