The information below, while
specific to Hollin Hills, also applies to
Hollin Hall and other homes that have chimneys constructed of used
brick.
One
of
the
unique
design
features
in Hollin Hills homes is the chimney.
Beyond adding an interesting design
element, the
chimney serves a dual function, housing the fireplace and flues, as
well as
offering a structural mass to brace the house against wind loading.
Brick
chimneys pose a special set of practical problems for the homeowner.
Their
way
Click images for larger view
The
unsightly "tin cap" fix.
Tin cap with bad brick
patch job.
New
cap,
drip
edge,
pointing,
and
counter
flashing. Click here for detail.
Please note: new mortar color matches old.
Click
image
for
larger
view Chimney
with
new sloped brick cap.
These brick chimneys
often experience several
interrelated problems due to the nature of the material and the design
of the
chimney. Typical problems include leaking between the chimney and the
roof,
water staining on the interior (living room) face of the brickwork,
blistering
paint and plaster where the ceiling meets the chimney, leakage into the
wood
box and/or fireplace, crumbling brick, and a disintegrating chimney
cap.
Many chimneys experience a combination of the problems above. All
of
these problems are caused by water entering the chimney structure
through
defects in the masonry, and through the flashing at the roof/chimney
joint.
Used Brick. To comprehend the problems and solutions,
one must
understand the structure and the material of the chimney. Brick
chimneys are
typically a hollow column of brick, enclosing the clay flue pipes from
the
fireplaces and in some cases, the furnace flue pipe. The top of the
chimney has
a mortar cap. Most brick in Hollin Hills, Hollin Hall and the
surrounding
neighborhoods is what is known as “used brick”. As the name implies,
used brick
is salvaged from the demolition of older buildings and is generally a
mix of
brick from different sources. The bricks in this area are from
demolished
buildings in DC and Baltimore. The original walls from which the bricks
were
salvaged were occasionally painted, thus the paint remnants on some
bricks.
When this brickwas originally
manufactured (around the turn
of the century and before)
the kiln baking process was uneven. In the kiln, brick close to the
heat source
was baked hotter and ended up harder with a dark red color. Brick that
was
further from the heat source was baked less and thus is softer and has
a
lighter, salmon color. These “salmon” bricks were originally used on
interior
walls and were never intended to be exposed to the weather. Their
softness
allows them to absorb moisture, and when that moisture freezes in the
winter,
the expansion of the water into ice causes the surface of the brick to
flake
off. Over time, the entire brick can flake away to nothing.
Unfortunately, when Hollin Hills, Hollin Hall, and
some of the surrounding neighborhoods were built, these salmon bricks
were
indiscriminately mixed with the darker brick. Virtually every chimney
built
with used brick has exposed salmon brick. Other exterior walls also
have salmon
brick, but this is a less serious problem as the bricks are shielded
from the
weather by the roof overhang. Disintegrating brick (a problem in
itself) also allows
water to penetrate the chimney structure and cause other problems. The
fix for
the crumbling brick is to cut out the bad brick, and replace it with a
non-salmon brick. In any given chimney, there may be just a few bricks
that
need replacing, or there may be dozens.
Chimney
cap. The
top of the chimney is covered with a cap of mortar which has often
developed
cracks. The porosity of the mortar and the cracks allow water to
penetrate both
the brickwork and the chimney cavity. A leaky cap is often the source
of water
dripping into the wood box and fireplace. In cases where the cap is
extremely
deteriorated, it should be replaced. To improve longevity, when
replacing the
cap, we use reinforced concrete rather than mortar. The new cap can
also
overhang the edge of the brick by an inch to provide a lip so water
running
from the cap drips clear of the chimney rather than running down the
face of
the brickwork. In cases where the chimney cap is fairly intact, we coat
it with
black roof cement (looks like tar) to make the cap waterproof. Where a
replacement cap is not necessary, water can be diverted from the sides
of the
chimney by adding a small metal drip lip. We add this lip on all four
sides of
the chimney by cutting a slot into the brick around the top edge of the
chimney. The drip lip is fairly unobtrusive when painted black to match
the tar
coating the cap. Our subtle drip lip is not to be confused with the
unsightly
tin lids with which so many Hollin Hills Chimneys have been disfigured.
Pointing. As
described above, leaky chimney caps allow water to seep into the top
rows of
brick. Through repeated freeze/thaw cycles, this moisture causes the
bricks and
mortar in the top few feet of chimney to separate from each other. The
separation creates cracks around the top of the chimney that allow even
more
water into the brickwork, thus accelerating decay. As water penetrates
through
the leaking cracks, leaking cap, and crumbled bricks and seeps
downwards, it
evaporates through the brick surface, leaving a white calcium residue
on the
brick face. Many hoemowners are familiar with this residue on
their
living room chimney wall. Our solution to the cracked joints is to
grind out
the cracked mortar and replace it with new mortar. This process is
called
pointing. Typically, only the top foot or two of the chimney needs to
be
pointed but in some cases, more pointing is necessary. We make sure the
color
of the new mortar is similar to that of the original mortar through
careful
combination of different sand colors and different cement colors.
Most of
the original mortar over time has darkened with dirt and mildew so it
may take
some time for the new mortar to acquire that aged patina.
Alternatively, the
entire chimney can be acid washed so all of the mortar looks clean.
Flashing.
The
final challenge with chimneys is the flashing joint between the chimney
and the
roof. The typical roof has a piece of sheet metal (flashing) that is
embedded
in the roof tar or shingles and runs up the face of the brick ten
inches or so.
The top edge of this metal is sealed to the brick with caulk or tar to
prevent
water from running down the brick behind the metal. However, the
durability of
this seal is entirely dependent on the integrity of the caulk. As soon
as the
caulk cracks or peels away from the brick, water can get behind it. A
typical
scenario is that the caulk joint crosses a crumbling salmon brick and
the caulk
peels away with the flakes of brick. The water running down from the
top of the
chimney and down the face of the brick is then funneled behind the
flashing and
the water continues its downward path, eventually running down the face
of the
brick inside the house. At the point where the ceiling meets the brick,
the
water soaks into the plaster, causing the plaster to flake and crumble
and the
paint to blister and peel. The water also continues to flow down the
face of
the chimney, leaving water stains, and in extreme cases, puddles on the
floor.
The typical roofer/handyman solution is to smear more tar over the
flashing
joint, which usually solves the problem only for the short term. The
permanent
solution we use is to cut a slot into the brickwork above the flashing,
and
install another piece of flashing that is bent into the slot, and then
bent to
overlap the piece of flashing below.
Conclusion.
Since
chimney leaks often have multiple causes, it is usually necessary to
use all of
the solutions above to ensure a dry and sound chimney. This means
coating or
replacing the cap, installing a drip lip at the cap, pointing up the
bad
joints, replacing the bad bricks, and adding new counter flashing. We
have
developed this holistic approach over the past twenty five years to
achieve a
complete, lasting, and visually pleasing remedy.
Photos and drawings of the solutions above are available below. (Click
images for larger view)
Their
way
Click images for larger view
The
unsightly "tin cap" fix.
Tin cap with bad brick
patch job.
Click
images
for
larger viewTypical
failed,
leaking
chimney cap. Typical
used
brick
chimney with decaying
salmon bricks, cracked mortar joints.
Typical unsuccessful attempt to
repair flashing leak. Click image for larger view
