bricks heat up, they have no room to expand, so
they crack and spall (flake).
Tools foR RAkInG MoRTAR
Although mortar analysis is the best way to
Before you can repoint joints, you must rake (cut back) old mortar, preferably without
match old mixes—historic preservation agencies
damaging surrounding brick. you’ve got several options:
can suggest mortar analysts—type O mortar
(described in “Mortar Types,” p. 217) should be a
TucK-pOiNTiNg (pluggiNg) chiSelS are usually thinner than mortar joints. used
close match for most old mortars. For this, mix
with a 2-lb. hand sledge, they’re slow but exact.
1 part portland cement, 2 parts hydrated lime,
aN 18-vOlT cOrdleSS griNder with a 41⁄2-in. abrasive wheel is the tool of choice
and 8 parts fine sand. The mix should be fairly
if you’re topside, raking out chimney mortar. There’s no extension cord to wrestle
stiff as mortar mixes go, keeping its shape when
with, and the tool has plenty of power—take care not to damage soft brick. Start the
squeezed into a ball. If the mix becomes too stiff
abrasive wheel in the middle of a mortar joint and gradually widen the cut.
to work, periodically sprinkle on and stir in small
pNeuMaTic air chiSelS represent a good balance of speed and control, but you’ll
amounts of water.
need to special-order mortar-removal bits. Trow & holden (Barre, vt.) offers a set that
If you’re repointing only a section of a struc-
includes 1⁄8-in. and 1⁄4-in. cape chisels, a 1⁄4-in. swept cape chisel, and a 4-tooth ripper.
ture, however, and don’t want it to stick out like a
sore thumb, experiment with combinations of
Of course, wear safety goggles and a respirator when cutting mortar.
mortar dye, cement, sand, and lime, carefully
labeling the proportions of each batch and allow-
ing it to dry for a month before committing to a
recipe. Masonry-supply houses stock such mate-
rials; they also carry new bricks manufactured to
but bricks remain firmly attached, repoint (or
look old should you need to replace bricks as well.
tuck-point) the joints by partially cutting back
the mortar, adding new mortar, and shaping the
Repointing technique. Using a spray bottle or a
joints. If the brick is painted, see “Stripping
brush, dampen the newly cleaned-out joints
Painted Brick” on the facing page. Finally, if
before applying fresh mortar. There are two ways
vertical or diagonal cracks run through several
to fill joints with new mortar. If you’re repointing
courses, there may be underlying structural prob- a relatively small area, use a bricklayer’s trowel
lems, which must be corrected before repointing. as a palette for the mortar and a tuck-pointing
In this case, consult a structural engineer.
trowel to push the mortar into the joint (see the
bottom photo on p. 230). Press the mortar firmly
Raking old mortar. For best results, rake out
so that it will stick.
(scrape out) mortar joints in an inconspicuous
If you’re repointing a large area, use a grout
area as a test, starting with the least destructive
bag to squeeze the mortar into the joint. A grout
tool. If the mortar is soft enough, an old screw-
bag looks like the pastry bag used to dispense
driver may be all you need. But if the mortar is as fancy icing onto cakes. You force the mortar out
hard as the brick, you’ll need to be patient. Cut
by twisting the canvas bag. But you’ll need strong
joints 1 in. deep, and try to cut a square trough
hands and forearms to twist the filled 5-lb. to
(not a V-groove) in the old mortar.
10-lb. bag. And you may need to thin the mix
Once you’ve raked the joints to the correct
slightly so it will flow easily through the bag.
depth, brush them out well, using a whisk broom After using a grout bag, you’ll still need to tuck-
or a wallpaperer’s brush, which you can also use
point the mortar joints.
to wet down the joints before adding fresh mor-
When the mortar has dried enough to retain
tar. Remove debris with an air hose or a heavy-
the imprint of your thumb, tool the joints. In
duty vacuum. Of course, wear safety glasses and
most cases, use a jointer that creates mortar
a respirator for this work.
joints the same shape as the old ones. Point the
The mortar mix. Try to match the old mortar
head joints first, then the bed joints. As you work,
mix when repointing an older brick building.
use a trowel to clean the mortar from the brick
Before portland cement was widely used, mortar
faces, but don’t disturb the mortar joints. Then
joints were usually a resilient mix of hydrated
wait two to three hours before using a stiff plas-
lime and sand, which compressed slightly as the
tic-bristle brush to remove the mortar still stuck
bricks expanded during summer and expanded
to the brick faces.
slightly as the bricks contracted during cool
weather. Soft, lime-rich mortars also show autog-
cleaning and sealing exTeriors
enous healing, an ability to self-repair hairline
Use the gentlest, least damaging cleaning agents,
cracks caused by seasonal temperature shifts.
chemicals, steam cleaner, or water pressure that
Mortar joints with portland cement, on the other works. Determine this by testing in an inconspic-
hand, are relatively hard and inflexible: As old
uous area. If the gentlest method doesn’t work,
222 chapter 9
move to the next strongest. If mortar joints are
Working MorTAr inTo JoinTs
eroded, a pressure washer may make them leak.
After cleaning, allow the brickwork to dry for two
to three days, then caulk gaps around doors and
windows and replace worn flashing. Safety note:
Whatever cleaning method you choose, wear a
option 1: let your bricklayer’s trowel
serve as a palette as you scoop mortar
face shield, rubber gloves, protective clothing,
from it with your smaller pointing
and a respirator.
trowel and press mortar into joints.
Cleaning brick surfaces. Get bids on hiring an
Two trowels are useful when
authorized cleaning service. Because cleaning
repointing old joints.
solvents can be hazardous and must be disposed
of according to Environmental Protection Agency
(EPA) and local environmental standards, hiring
professionals will spare you those headaches.
Moreover, the service will be responsible for
achieving the desired results, however long it
takes. If you’ve got a tight budget or an adventur-
ous spirit, consider the DIY options described
option 2: or you can use a grout bag
next; they’re listed more or less in order of gentle-
if you’ve got a lot of joints to fill. But
ness. Wear saf
ety goggles and rubber gloves for
this is hard work: The bag is heavy,
all procedures, and read operating manuals care-
and you need to twist hard to force
the mortar out a small opening—a bit
fully before using pressure washers, steam clean-
like wringing water from a stone.
ers, and the like.
Use a garden hose to soak the surface, and
then scrub with a nylon scrub brush. The warmer
the water and the longer the soak, the more dirt
you’ll remove.
If the hose wash isn’t sufficient, try a pressure
washer on a low setting. Increase the pressure
slightly—say, to 300 psi to 400 psi—and you’ll
remove yet more. Note: If you see sand in the
Here, a bullhorn jointer compresses
mortar joints.
runoff water, lower the machine’s pressure set-
tings immediately. Otherwise, you may be strip-
ping the mortar joints. Likewise, monitor the
inside of the building, especially around win-
dows, for leaks; it’s easier to lower the pressure
than to replace drywall.
Steam cleaning is especially effective if sur-
faces are mossy or have ivy “trails” or built-up
grime. Although somewhat slower than pressure
washing, steam doesn’t generate the volume of
runoff and won’t penetrate as deeply into brick
surfaces or cracks.
stripping PAInTeD BRICk
If you’re in an urban area where soot and auto
exhaust have soiled the building, try a nonionic
if you intend to repoint a painted brick wall, strip the paint first—no small job. For
detergent with a medium pressure (1,000 psi)
this, rent a pressure washer. ask the rental company to recommend a tip size and pres-
next. Nonionic detergents such as Rhodia®’s
sure—1,800 psi to 2,500 psi is common for stripping—and show you how to use the
Igepal® and Dow®’s Tergitol™ and Triton™ won’t
machine safely. Buy heavy-duty tarps, too. Caveat: removing paint by any method
leave visible residues, as household detergents
makes a prodigious mess.
and trisodium phosphate (TSP) will. Again, scrub
at the job site, test the washer on an out-of-the-way area first. if the stripped brick
with a synthetic-bristle brush, and rinse well.
doesn’t look so great, rethink stripping it. The brick may have been painted in an
If these methods don’t produce the results you
attempt to protect crumbling mortar joints and eroding brick from further weather-
want, proprietary chemical cleaners are the next
ing. Finally, never sandblast old brick: Sandblasting equipment will destroy brick in a
step. They usually involve a three-step process—
flash, and it’s dangerous to use.
wetting surfaces, applying the cleaner and scrub-
bing it in, and then rinsing—repeated as many
times as needed. If you apply the cleaner, follow
Masonry
223
the manufacturer’s instructions to the letter.
siloxanes, and silane/siloxane blends. Both pre-
P R O T I P
Instructions will be quite specific about safety
mixed and concentrated coatings are available—
garb, dilution rates, dwell times (how long the
typically applied in several coats. Some water-
although it may seem counter-
chemical remains on), washer settings, and tem-
repellent coatings double as graffiti barriers,
intuitive, start washing brick
perature ranges (most don’t work well below
although they tend to be shiny.
walls at the bottom and work up,
50°F). Before committing to a cleaning system,
Waterproof coatings come closer to being true
keeping the whole wall wet as
you progress. if the entire wall is
visit the manufacturer’s website and call its tech-
sealers because they’re usually pigmented or
wet, dirty water and diluted
support number.
opaque and form a thin elastomeric (flexible)
cleaners running down won’t
film. Chemically, they run the gamut from water
Sealing exteriors. Are water-repellent or water-
streak the cleaned sections, but
based to bituminous. Bituminous varieties are
proof coatings necessary on exterior masonry
dirty water and chemicals run-
widely applied below grade on building founda-
walls above grade? Mostly, no. There may be a
ning over unwetted dirty sec-
tions and, to a lesser extent, to interior basement
few 200-year-old buildings in every city whose
tions will leave marks.
walls where mild leaks have occurred.
porous brick would benefit from being coated,
but most masonry exteriors won’t admit water if
rain is directed away from the structure by gut-
Chimneys
ters, downspouts, and other standard drainage
Masonry chimneys are freestanding units that
details and if the masonry is properly flashed,
carry exhaust gases out of the house. To prevent
caulked, and detailed.
superheated gases from escaping, chimneys
Exterior sealants, loosely divided into water-
should be tile lined and free from cracks or gaps,
repellent and waterproofing coatings, don’t fully
or they should have insulated stainless-steel
seal masonry surfaces, nor would you want them flues. Annual inspections and maintenance are
to. A perfect seal could trap water inside the
crucial to chimney health: If you discover mortar
walls. Moreover, masonry walls with water
or flue tiles that are cracked or missing, the
trapped inside and walls that are wicking mois-
chimney is unsafe. Chimney flashing and roof
ture from the ground will, in time, exude soluble
safety are further discussed in chapter 5.
salts in the masonry as powdery white substances
These days, new and retrofit chimneys are
called efflorescence.
often nonmasonry. There are several reasons
Water-repellent coatings, which are typically
for this transition: building code and insurance
clear, penetrate masonry pores and keep rain
requirements; a shrinking pool of qualified
from penetrating to a large degree, while allow-
P R O T I P
masons; and the inherent inflexibility and
ing water vapor from living areas to escape
tendency of masonry to crack and compromise
through the wall. Most water-repellent com-
in spite of recommendations
safety when structurally stressed. Perhaps most
pounds are water based, formulated from silanes,
you may get from store clerks or
important, a host of safe, cost-effective, and
old-time masons, don’t use muri-
atic acid to clean masonry sur-
faces. its fumes are noxious. it
can burn your skin and, if you get
openings in Brick Walls
it in your eyes, blind you. it also
etches the surface of stone,
if you want
to add a door or window to a brick wall, hire a structural engineer to see if that’s feasible.
brick, and mortar joints and
if so, hire an experienced mason to create the opening; this is not a job for a novice. if the house was
weakens their ability to shed
built in the 1960s or later, the wall will likely be of brick veneer, which can be relatively fragile because
water. and it stains.
the metal ties attaching a brick veneer to wood- or metal-stud walls tend to corrode, especially in humid
or coastal areas. in extreme cases, steel studs will rust, and wood studs will rot. When opening veneer
walls, masons often get more of a challenge than they bargained for.
Brick homes built before the 1960s are usually two wythes thick (with a cavity in between), very
heavy, and very likely to have settled. undisturbed, these walls may be sound, but openings cut into
them must be shored up during construction, adequately supported with steel lintels, and meticulously
detailed and flashed. Moreover, creating a wide opening or one too close to a corner may not be structur-
ally feasible, so a structural engineer needs to make the call.
To close off an opening in a brick wall, remove the window or door and its casings, and then pry out
and remove the frame. Prepare the opening by toothing it out—that is, by removing half bricks along the
sides of the opening and filling in courses with whole bricks to disguise the old opening. The closer you
can match the color of the existing bricks and mortar, the better you’ll hide the new section. as you lay
up bricks, set two 6-in. corrugated metal ties in the mortar every fourth or fifth course, and nail the ties
to the wood-frame wall behind. leave the steel lintel above the opening in place.
224 chapter 9
easily installed insulated metal chimneys are now
available. That noted, the review here is limited
about chimney Fires
to masonry chimneys.
The root cause of a chimney fire is the imperfectly burned material in wood
cleaning a cHiMney
smoke that condenses and sticks to the inside of a chimney. creosote is a sticky
Chimneys and their flues should be inspected at
brown or black substance that may harden to the consistency of glass. incomplete
least once a year and cleaned as needed—ideally,
combustion also produces tar, ammonia, methane, carbon monoxide, toluene, phe-
before the heating season. Better chimney-
nol, benzene, and eventually, turpentine, acetone, and methyl alcohol.
cleaning services will get up on the roof, inspect
Renovation 4th Edition Page 52
