My original shingle roof has lasted 24 years, problem free. Now, I am
planning to have a new roof installed (after tearing off the old) and I
am learning there is way more to this than meets the eye! One issue is
flashing around my brick chimney .
The current flashing is galvanized steel. There has been no leakage.
About 15 years ago I went up there and painted it because it showed
some unsightly rust. The paint job still looks good.
Most re-roofing bids I've received have included new chimney flashing
and I've never questioned that until I got the latest bid from a
reputable contractor. He told me that he would be glad to reflash the
chimney (for $450), but that it didn't need to be done. He said a good
galvanized flash job would last forever, if painted.
Further, he commented that the dormer up on the roof (75% of chimney is
inset in the dormer) was built around the chimney, and it would be
difficult to do as good a flashing job as the original effort. (He did
indicate that he could do a good job. It's just that he didn't think it
I've done a fair amount of Google research on flashing. Many folks have
suggested replacing valley flashing when re-roofing, but I've found no
discussion on the pros and cons of reflashing a chimney versus keeping
the old, problem-free existing flashing. I get particularly concerned
when I read all the horror stories of flashing jobs gone bad.
All I want is a good job, and the piece of mind that comes from knowing
that the new roof and related work will last, and be problem-free. What
do you think?
The roofer told me the same thing. He said the flashing is in excellent
shape and didn't need it done. It was done back in the day when everything
was done with quality work. You have to wonder what material is available
today - aluminum foil?
He's a reputable roofer so I followed his advice and kept the same
If you saw rust it is deteriorating even with paint sealing it. Have it
redone but be sure they cut into mortar joints and mortar it in. Copper
is best. Lead and copper last a lifetime not galvanised steel. Many
roofers don`t know how to flash or will cut corners, hire someone who
knows . The guy that said galvanised lasts a lifetime does not.
I can't see your chimney from here but based on the mention of the dormer I
will assume that at least one side of your roof has a rising grade to the
chimney. Ask the contractor how he plans to deal with the step flashing
along those sides.
A properly flashed wall or chimney in this situation has step flashing and
over flashing. The step flashing prevents water on the roof from getting
into a crevice and the over flashing prevents water on the chimney from
getting behind a crevice in the step flashing. As illustrated by the crude
ANSI drawing below. This drawing assumes that the chimney is on the left of
| = overflashing is mortared into the chimney
|__ = step flashing forms an L between the chimney and the roof. One piece
is installed for every course of shingles. How you could remove the
shingles without destroying the flashing is beyond my ability to understand.
Even if they just butt the shingle up to the chimney with no flashing and
add a little caulk, it will be few years before you have a problem. If they
leave the overflashing in place and add some caulk it will be longer before
you have a problem but you will before your shingles wear out.
If you are just doing a nail-over, you should do a bit more research before
you sign a contract for this option.
I do agree with the statement that the old may be better than the average
sold on today's jobs IF it properly utilized. The quality goods are still
sold. Most people are to cheap to pay for them.
You've had some suggestions, and I'll add a little bit more to it.
Chimney's often leak. We all know that. Why do they leak? Because they
were either not flashed or not flashed properly. How do you do that?
One reply gave pretty good details on that so I won't go into it any
more than to say that oftentimes it is a good suggestion to seal
between the shingles and the step-flashing you install with every
course of shingles just as an added precaution (which is oftentimes
warranted.) Really, though, it is usually not the straight edges of
the chimney where the leaks develop, although that happens sometimes,
rather it is at the corners where the ability of the installer is most
important and how he works the metal in these locations will either
give you a headache or you will be blissfully unaware of how good a
job he did since you've never had any problems at all.
As to the question of should the existing flashing that is installed
in the mortar be replaced? I can't answer that question from here...no
one can. Good, heavy gauge galvanized steel will last decades in this
application. Thin galvanized will rot in a few years. I've seen some
that are in almost new condition after decades of service and don't
warrant replacement and to do so would gain the homeowner nothing but
a lighter pocket-those we don't replace. If it is at all questionable,
and many are, then they get replaced. How? We use a worm drive Skil
saw with an abrasive blade to cut a groove into the mortar, fashion a
new piece of metalwork, and install it using a urethane sealer made
for sealing this kind of exterior joint. I've never seen a good
installation using this method fail. In North Texas sun and extremes
of weather. Sure, if you could find a mason to do such a small job,
you could mortar it in, maybe the new mortar would match the old (the
sealer we use comes in a wide variety of colors and one will match
most any mortar), but maybe not, and in my opinion, the added expense
of the mason isn't warranted since the urethane sealer does such a
good job in and of itself. I've seen bad mason repairs not last as
long as this stuff will.
In short, you need to ask yourself a question...Do you trust the
roofer who said, in effect, sure I could charge you more money
(thereby making more money for myself) and change it out, but the
materials in place are in fine shape and you don't need to spend that
money and I'm going to tell you this straight up.
And yes, with proper painting it will last as long as your new
roof...if the condition it really is in is as good as I believe it to
be sight unseen. You can even treat that rust with some products on
the market today that will stop it in its tracks and it won't spread
any more...if you want to go to that much trouble. And I'm not talking
about Naval Jelly or Red Lead. There are some great products out there
that will stop rust dead in its tracks.
Use your best judgment. If you, and your roofer, are wrong, later it
is perfectly possible to replace the flashing. But I suspect it won't
Good luck and I hope this helps.
(Remove the Primes before e-mailing me)
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