2-3 (Basic to Moderate)
Bruce W. Maki,
||This chimney was ready to disintegrate. All of
the bricks in the top 5 rows were loose.
|Much of the mortar was gone.
||Large pieces of mortar were loose.
|Some bricks had split completely.
I suppose that most masons would simply rebuild this chimney from
the roofline up, but the homeowner needed a quick and simple fix to
last a year or two. The chimney is no longer used for a furnace, and
has a wood burning fireplace connected to it.
I am not an expert in masonry, but I do have enough knowledge to
be dangerous. I cannot recommend that you follow the methods used
here. Consider this article to be for entertainment value
||I used a screwdriver to remove some of the loose
crumbs of mortar.
||The materials, from left to right: Type N
masonry cement, a bucket of sand, a small 1 pint pail for
measuring, and a mortar mixing tub.
|I dumped some sand in the mixing tub.
||I estimated that 12 pints of sand would be
|I added masonry cement to the sand, 6 pints. A
2:1 ratio of sand to cement has always worked for me.
||I used a hoe to mix the dry powdered
|Then I added water and mixed until the mortar
was the right consistency.
||The mortar was still too dry. I can tell by the
|The mortar slid off the trowel when tipped
One indicator of proper mortar consistency is it's ability to
stick to the trowel. Some general rules that I am aware of:
- The mortar must stick to the trowel when the trowel is held upside
- The mortar should, ideally, stick to the trowel when it is
- When held sideways and given a little flinging motion,
the mortar should slide off the trowel.
||I dumped the mortar into a plastic pail
|Up on the roof, I laid out the tools and
materials near the work area.
I trimmed the small end of the pastry bag to enlarge the opening,
making it about 3/8" in diameter.
||I sprayed water on a small area, about 1 foot
|I loaded the pastry bag with a little mortar.
The Fun Part:
||I was completely inexperienced at this. I
had never even used a pastry bag for applying cake icing.
I simply stuck the nozzle in a hole and squeezed.
|I stuck the nozzle in deep and withdrew it as I
squeezed out the mortar.
||I found that it helped if I occasionally gave
the bag a downward jerk, to make the mortar settle into the
I also had to temper (add a little water to) the mortar in
the plastic pail, to keep it creamy enough to flow out of the
The tuckpointing took about an hour. I had to re-wet the brick
often. The dampness of the masonry is critical. It needs to
be almost saturated on the surface, but not shiny-wet. If the
surface is too dry, you'll know it, because the mortar will not
Also, if the masonry is too dry, it will absorb water from the
mortar, causing it too bond poorly, fall off, or develop tiny cracks
from excess shrinkage.
||When the mortar joints were all filled, I used
my finger to press in the joints and smooth out the mortar.
This is called "tooling the joints".
There are many different ways to tool the joints. Some techniques
use a little rake-like device to scrape excess mortar out and leave
a uniform depth recess. This homeowner only wanted the chimney to
stay together for another year, so I did the simplest thing, a
flush, finger-tooled joint.
Tooling the joints causes the mortar to compress and be bonded
better to the masonry. I kept wetting my finger to help this bonding
There is an inexpensive spoon-like device for tooling masonry
joints, but I didn't have it with me.
||A few minutes of joint tooling and I was done.
|After the mortar had dried for an hour, I came
back. Using a small whisk broom with a pail of water, I
carefully cleaned the excess mortar from the faces of the
Then I used a garden hose to clean all the spilled mortar from
the roof. Mortar comes off easily with water and a little
scrubbing, for an hour or two after being mixed.
I think the best way to deal with old crumbling masonry chimneys
is to simply destroy them. Demolishing a chimney like this takes a
couple of hours with a small sledge hammer. There are many metal
chimney flue products on the market that will perform better and
longer than masonry.
- The Homeowner's Guide To Building With Concrete, Brick
- Author: The Portland Cement Association
- Publisher: Rodale Press, 1988
- ISBN 0-87857-795-5 Hardcover
- ISBN 0-87857-795-3 Paperback
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What's New Project
- Small Trowel
- Vinyl Pastry Bag
- Plastic Pails
- Water Sprayer
- Mortar Mixing Tub, Hoe
- Masonry Cement, Type N
- Clean Sand