Masonry Magazine February 1993 Page. 60
Chimney Cap
A chimney cap is used to pro-
tect the chimney from rain or snow
and, when the building is located
below adjoining buildings, trees, and
other obstacles, helps prevent down-
drafts. It must have at least two sides
open, with the open areas larger than
the flue area. The hood could over
hang the chimney wall a few inches
with a drip slot, in lieu of the cap, to
keep the wall dry and clean.
Chimney Construction
In order for a chimney to develop
an effective draft, the top of the flue
should extend a minimum of two feet
above the ridge or two feet above
any roof surface within ten feet hori-
zontally and at least three feet above
the highest point at which the chim
ney passes through the roof.
To insure against condensation of
flue gases, the temperature of the
products of combustion leaving the
chimney should be at least 250 de
grees fahrenheit. Portions subject to
excessive cooling could be insulated
or otherwise protected from exces
REPRINTED, with permission, from "Tek
Spec #20" published by the New York State
Concrete Masonry Association, 6 Airline
Drive, Albany, New York 12205.
sive heat loss with a non-combustible
rigid insulation placed on the outside
of the chimney.
To prevent possible entry of mois-
ture from the outside, the exterior of
the chimney should be waterproofed.
This would help eliminate exterior
deterioration of the masonry units
due to external freezing conditions.
During construction, care should
be taken to adequately anchor the
chimney to the building.
During the normal operation of a
wood burning stove, temperatures in-
side the chimney flue near the flue
ring (thimble) can reach several hun-
dred degrees, while the exterior of
the masonry remains at freezing tem-
peratures. It is possible that thermal
stresses developed by thiş situation
could cause damage to the masonry
units. When your stove is cold, you
should allow sufficient time for the
chimney to adapt to higher tempera
tures. Start a wood fire slowly and
allow at least two hours for the stove
to reach operating temperatures to
minimize the danger of thermal shock
cracking the flue or flue ring.
Creosote Buildup
One method for reducing creosote
buildup is to gradually stoke a me-
THE POLY LINE
CONCRETE MIXER
* Removeable/replaceable poly liner with molded blades.
* Easy removal - no tools required
GILSON
MIXERS
Manufactured by C-F Gilco
P.O. Box 326
Cedarburg, Wisconsin 53012
SPECIAL FACTORY PRICING: 1-800-445-2699
A Construction Forms Company
* Steel outer drum
* Heavy duty construction
* Wide choice of power options
60 MASONRY JANUARY/FEBRUARY, 1993
dium hot fire for fifteen to thirty min-
utes at least once a day, which tends
to burn off the creosote in small
amounts. Seasoned, or dry wood will
form less creosote deposits than un-
seasoned or wet wood. In mild
weather, frequent slow burning of the
stove will severely aggravate the cre
osote problem. Thus, the more effi-
cient the stove, the more creosote is
capable of being produced.
Frequent inspction of stoves and
chimney flues is important, espe-
cially during the first season a stove is
used. That way any problems that
may be occurring can be discovered
and corrected. If it's an airtight stove.
the stove pipe and flue liners should
be checked each week. Inspect chim-
neys from the roof, using a flashlight,
or use a mirror in the cleanout to look
up through the chimney flue. Check
stove pipes by tapping them with a
metal object. If you hear a dull thud
rather than a metal ping, it means ma-
terials are accumulating. Any time an
inspection shows soot or creosote
buildup, the chimney and stovepipe
should be cleaned.
LABOR SUPPLY
Continued from Page 36
gaged in some type of activity. But all
activities are not equal; some are pro-
ductive and some are not. Most activ-
ities can be classified as one of three
activity types: primary, secondary, or
recoverable lost time.
Primary time is putting work in
place right the first time. Secondary
time is work preparation; i.e., getting
tools, receiving instructions, looking
at plans and moving materials. Re-
coverable lost time is rework, wait-
ing, late starts, long breaks and so on.
Most people would assume that pri-
mary work time on most jobs is very
high-in the seventy to eighty per-
cent range. However, after thousands
of observations on hundreds of jobs.
FMI calculates that primary time av-
erages about thirty-three percent,
with the remainder of the day spent
in secondary and recoverable lost
time.
Surely, with primary time as low as
one-third of a day, there is a signifi-
cant loss in productivity. If the con-
struction industry could increase pro-
ductivity every year by slightly more
than four percent from now until the
year 2000, the increased productivity
would offset the need for more work-
ers.
Is the manpower shortage caused