As you may know, flashing is a
protective element every roof needs to shield edges, valleys,
corners, and similar areas where the shingles can't provide adequate
protection. Chimney flashing is one of the more complicated flashing
types on your roof.
Chimney flashing typically has two
layers that overlap each other, and they're shaped differently on the
front, sides, and back of the chimney. This complicated flashing
system may seem a bit like overkill, but in truth, the chimney
flashing has some of the hardest jobs anywhere on your roof.
Here are some of the hats your chimney
flashing has to wear.
1. Chimney Flashing Resists Rain
The edges of your roof (both those at
the eaves and gables and those at roof penetrations such as the
chimney) are your vulnerable spots because the shingles can't protect
them.
The spot behind your chimney is
especially problematic. Rain runs right down to this spot and may get
caught against the back of the chimney, where it can create a pool of
water. Standing water can more easily cause roof leaks because
instead of draining off the roof, it can be pulled through the roof
by gravity.
The pond effect can be especially
enhanced if dead leaves fall on the roof and get caught behind the
chimney. Your roof contractor may include a waterproof membrane in
this spot as part of the chimney flashing system. In some cases, your
contractor may install a special roof piece called a chimney cricket
to help divert rain.
2. Chimney Flashing Excludes
Wildlife
Chimneys and other roof penetrations
are often favorite spots for wildlife to force their way in. That's
because the roof deck has a cut-away hole around the roof penetration
to allow the vent pipe, chimney, or other roof feature through.
Wildlife can sense the warmth from the
attic easily in those spots and start attempting to tear through.
Properly installed metal chimney flashing can help to deter animals
from clawing their way into the attic near your chimney.
3. Chimney Flashing Resists Heat
Unlike your bathroom vent exhaust
point, the flashing around the chimney has to be able to withstand
heat from a fire.
Although the fireplace is far below the
roof itself, it can transmit huge amounts of heat up through the
bricks. Much higher temperatures can result if a chimney fire occurs
(and often, you may have a chimney fire without even knowing it). So
the chimney flashing has to be made of non-flammable material such as
metal or it could become a fire hazard.
4. Chimney Flashing Allows for
Settling and Expansion
The bricks in a chimney can expand and
contract by tiny amounts when they heat up and cool down. Likewise,
the asphalt shingles on your roof can expand and contract slightly as
they heat up in the sun's heat and cool down to ambient temperatures
at night.
Brick and asphalt may expand and
contract at different speeds, so any single object trying to bridge
the gap would work loose or crack under the strain. This is one
reason why chimney flashing has to be made of two separate pieces
that glide slightly together or apart. Another reason is to allow for
adjustment in case the chimney settles slightly over time.
As you can see, the demands on your
chimney's flashing system can be huge and the stakes can be high.
This is why you need to choose an experienced roof contractor who
doesn't just know how to lay shingles but can correctly install the
right types of flashing around your chimney and other roof features.
For more information on the types of
roofing materials we can install and the other roofing services we
offer, get in touch with Whittle's
Roofing Co., Inc., today.
