Failing Concrete
Caps
Weather conditions playa major factor in
failing caps i.e.
Rain, snow, freezing, thawing and heat
Durability
of masonry is the main reasons caps have lasted for many years
Causes for
failure
-
Most exposed and only
horizontal surface
-
Area most likely to absorb
water
-
Assuming flashing is properly
installed
-
Same mortar used as when
brick were laid
-
Normally application is put
on too thin
-
Directly bonded too flue tile
-
Concrete shrinks as it cures
-
During curing process cracks
form
-
Mortor around chimney should be tapered to a feather edge
-
Thin edges cannot hold up in
severe weather
-
Deterioration occurs and
starts to collect water
-
Cap is rarely isolated from
flue liner
-
In winter months; flue tiles
expand in upward direction
-
Cap is bonded to frozen exterior bricks
-
Connected caps during flue
expansion can crack
These four conditions ultimately allow water
to get in thru cap. Every year that deterioration occurs, more damage is done to the
top of the chimney and to the cap. Eventually, water can make it's way into the
house and cause severe damage at large.
Wisconsin Administrative Codes States...
(8) CHIMNEY CAPS. Chimneys shall be provided
with precast. or cast-in-place concrete chimney caps. Chimney caps shall have a
minimum thickness of2 inches, shall slope outwards away from the flue, and
shall provide a one-inch overhang and drip edge on all sides. A slip joint
shall be installed between the flue and the cap. The slip joint shall be filled
with 1/4-inch felt or similar mate- rial and shall be caulked with
high-temperature caulk or similar material to prevent water infiltration.
(Issued May - 2005)
