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Building a cricket (or saddle) on a
chimney
When building a cricket on a
chimney, do the edges of the cricket go all the way to the edge of the chimney or are they
set back from the edge to allow for flashing? If set back, how far?
The cricket may be built either way
I run mine out to the edge of the chimney to ensure that when the flashing is added the
water is run well away. You should remember to maintain your 1" clearance from
combustible material for fire protection. The flashing will serve as the fire stop.
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Masonry Chimney repairs
The chimney on my 30 year old house
has crumbling mortar on the top 6 rows. It appears to be stable from this point
down. What type of mortar can I use to repair this? Are there any hints I can
get? Can I just run up with a trowel, straight edge and some mortar? Are the liner bricks likely to
need remortaring?
What usually happens is the mortar
will breakdown from where the chimney leaves the attic. This is caused by the temperature
difference creating moisture and chemical breakdown from the burned fuel. I recommend
taking the chimney down to the flashing and replacing it inside and out. You can use
either a type S mortar (1 part portland 1/2 part lime 4 1/2 sand)or a type N ( 1 part
portland 1 part lime 6 parts sand). You can buy this in bags by type and just add sand.
Check the rest of the chimney for cracks inside and out but it will most likely be just
the top and should be simple to replace.
Chimney chipping
My Chimney is being chipped away
little by little in various spots, it seems as if the outside face of the red brick is
just being shaved off by the elements of weather. How can I re-patch the faces of these
bricks around the chimney, and with what? it almost looks as if birds are pecking at
different bricks along the top and base of chimney.
Your right the brick are being
broken down by the elements. The problems you are describing happen most often from water
penetration. As far as patching the brick the only thing to do is replace them. Check the
chimney cap for cracks and seal the new brick with a quality sealer and the problem should
not come back.
Masonry block chimney
I would like to put up masonry block
chimney with a clay liner. Any information on installation from footings to cap.
A check of local fire and building
codes in your area should be your first stop. In most areas code requires that masonry
chimneys have a minimum cross-sectional area of 50 square inches. Have a minimum clearance
of 1 inch from any combustible material. This 1 inch air space must be filled at each
penetration of floors or ceiling with a non-combustible material like fiberglass
insulation or plaster.
If your chimney is to be built outside of
the house your footing also must be placed below the frost line in your area (normally
where frost is a problem this is between 4 and 6 feet down). Your footing should be twice
the width of the block you are laying and I recommend 12" thick. Measure 8" or
one block from ground or floor level put in a cleanout door next determine what height to
place your thimble (where your stove pipe enters the chimney)local codes vary on this also
rule of thumb says 18" below ceiling to top of pipe.Once this is determined measure
down from the ceiling 18" plus diameter of the stove pipe plus 12" this is where
you start your flue liner. The best way to do this is to get some cement brick cut them so
when laid they project into the chimney to the inside of the flue liner without leaving
too much of a ledge inside. Laying the next chimney block will keep them in place and
support the flue.
A second course of brick will offset the
joints in the flues and block. Cutting the flue liner is complicated if a pre cut one is
available take it. Fire clay for your flues should be an air set type because normal
chimney temps won't be high enough to set heat set material. Your flashing should be in
two parts one L shape under the shingles and up the sides of the chimney one out of the
chimney and down to within 1/2 to 1" of the sub flashing or shingle. The chimney
should terminate 2' above the highest point within 10' of the chimney(unless local code
says different).There should not be more than 8" of flue exposed above the cap.
When pouring the cap wrap the flue with
fiberglass to leave about 1/2" expansion (caulk later with fire proof caulking)and
mix the concrete as dry as possible to prevent cracking.
