A few years ago, after I'd been doing whole-house restorations
for more than two decades, I started getting calls from clients
who just wanted old windows repaired. At first I took on these
jobs to fill in periods of downtime between the larger
projects. But after I'd done a couple of them, the trickle of
calls became a torrent. Some callers were simply hoping to
qualify for generous new federal and state rehabilitation tax
credits. Most, however, had learned to appreciate the precise
joinery, wavy glass, and unique divided-light patterns that
made their original windows so valuable. Now all I do is
Long-neglected windows may be inoperable and unsightly, but the
damage is almost always superficial — peeling paint,
cracked putty, broken glass, frayed cords, frozen pulleys
— and relatively easy to fix. Most old windows in my area
were crafted from long-leaf heart pine, which is a remarkably
stable and rot-resistant material. Although it's not unusual to
find localized outbreaks of rot, especially in end grain that's
been long exposed to the weather, these areas are easily
repaired with epoxy.
In my experience, once the surface issues have been addressed
and the moving parts properly tuned, a century-old window will
operate as smoothly as any modern unit — and look a whole
Unless I'm asked to perform a minor fix, such as reglazing an
otherwise first-rate window, I always remove the sash and take
them back to my shop for repairs. To access the bottom sash, I
cut the paint line where the window stop meets the frame. I use
a small pry bar backed by a stiff-bladed putty knife to pop off
the stop (without marring the frame), then cut the old sash
cords and lift out the bottom sash.
Removing the parting bead that divides the top sash from the
bottom is always a challenge because it's set in a groove, so
there's no easy way to slip a pry bar underneath and force it
out. I've had some success using a painter's 5-in-1 as a
makeshift prying device. Another strategy is to clamp the face
of the bead in a Vise-Grip locking sheet-metal tool (Irwin,
800/464-7946, www.irwin.com) and yank it out (see Figure 1).
Fortunately my lumberyard keeps parting bead in stock, so I
don't panic if I break one from time to time.
Figure 1. A set of wide-mouth Vise-Grips
helps extract parting bead without undue damage.
Even though they're designed to be as operable as bottom sash,
most of the top sash I encounter are painted totally shut. I
separate the paint seal with a sharp utility knife (a small saw
called a window zipper makes this task a bit easier — but
it's another tool to keep track of, and I prefer to keep things
simple). If the sash remains stuck after the paint lines are
cut, I look around for the screws or nails that a previous
carpenter must have installed.
Whenever I'm dismantling several windows at the same time, I
mark the unfinished vertical edge of each sash with a code to
ensure that it goes back in the proper jamb. Since the edges
should never be primed or painted, a pencil mark is sufficient.
In many cases, when I've looked closely, I've found that the
original installation codes were still visible.
Before returning to the shop with the sash, I remove any paint
that may have accumulated on the inside running surfaces of the
window frame. I've tried dozens of paint removers over the
years; my favorite is the Speedheater (Eco-Strip, 703/476-6222,
www.eco-strip.com), which uses infrared light to soften paint
as effectively as a conventional heating device, but at a much
If the metal pulleys are also encrusted with paint, I remove
them and let them soak in a 1-to-1 mixture of Simple Green and
ammonia. After several days, I'll rinse them with water to
remove the accumulated paint.
Because they lack moving parts, window frames are much less
susceptible to wear and tear than sashes; just the same, rot
never sleeps in this part of the country, so I poke around
every surface with a 5-in-1 to check for signs of sponginess. I
treat minor infestations of rot with an epoxy repair system
(System Three Resins, 800/333-5514, www.systemthree.com).
Before returning to the shop, I cover the empty jamb with
insulating foam board to keep out the elements, or with plywood
to keep out the riffraff.
Once I've decided to bring a sash back to the shop for repair,
I strip it down to bare wood, then sand, prime, paint, and
reglaze it. The old glass is often filthy and badly stained
from decades of pollution and rainwater; since I don't want to
wait until the soft new putty is in place, I give the glass a
serious cleaning before I take it out. With the sash laid flat
on the bench, I apply a generous coating of liquid glass
cleaner, then run a safety razor back and forth over the
surface of the glass before polishing it with a cloth.
I use the Speedheater to soften up the glazing at the same time
as the paint. To protect the glass from rapid temperature
swings (which could cause cracking), I cover it with a scrap of
hardboard wrapped in aluminum foil (Figure 2). After exposing
one 14-inch section to the heat for about 60 to 90 seconds, I
slide the unit down the rail and scrape away the loosened paint
and glazing compound. To remove the glazing compound without
damaging the glass, I use an Eco-Strip chisel with an attached
wheel that serves as a depth stop.
Figure 2. Placed over a heat shield to
protect the glass, an infrared paint remover softens up the
glazing compound and paint (top). After a minute or so, both
materials release their grip on the wood and can be quickly
scraped off (middle). A special chisel with an adjustable guide
wheel removes glazing compound without harming the glass
When the glazing is out, I carefully extract the glazier's
points with a small pair of needle-nosed pliers. To properly
prime the sash, I try to remove all the old glass panes; then I
set them aside in a secure place until it's time to put them
back in. I hate to break irreplaceable glass, so if a
particular pane remains stubbornly bonded, I leave it and work
To replace cracked or broken panes, I keep a supply of antique
glass on hand, which I can cut to size as needed. Most of my
stock is reclaimed from windows that were too badly damaged to
save, or was purchased from a local salvage yard (which also
ships by mail order; www.caravatis.com). In addition, I'm aware
of two manufacturers who reproduce various types of antique
glass: Bendheim (www.bendheim.com) and Artisan Glass Works
With the glass out of the way, I repair any minor rot damage
with an epoxy wood repair system. After allowing the epoxy to
cure (usually overnight) and tooling the patch smooth, I
lightly sand all surfaces with 100-grit sandpaper. Then I apply
a generous coating of Benjamin Moore's Fresh Start — an
alkyd primer suitable for both interior and exterior uses
— to all surfaces except the vertical edges. I'm
especially careful to fully coat the rebate (the part that
holds the glass) because the glazing compound will not bond to
Once the primer has dried, I spread a thin frosting of glazing
compound on the rebate, then gently press the glass into place.
Instead of push points that stick out and catch my knife when
I'm tooling the glazing compound, I use triangular glazier's
points to secure the glass. With a putty knife, I push the
points into the wood just far enough for them to be covered by
the new putty. For small panes of glass, such as you'd
typically find in a 6/6 window, one point in the middle of each
mullion is sufficient. On larger pieces, I leave about 12
inches between points.
Before applying the glazing compound, I clean the glass one
last time to make sure I've left no paint or putty on the
surface, then apply a coating of NoStreek Glass Polish
(Gel-Gloss, www.gel-gloss.com), which adds a brilliant sheen
and helps repel dirt.
Nothing is more crucial to the success of a sash repair than
glazing compound. I use a professional-grade product called
Perm-E-Lastic Glazing (Atlas Putty Products, 800/373-2727,
www.putty.com) that spreads easier and remains more elastic
than over-the-counter versions. I tool the compound with a
curved putty knife — technically called a 35-degree bench
glazier — which I find easier to control than a
straight-bladed knife, especially when working in corners. I
bought mine online from a supplier of glazing products, but it
took a bit of searching (Ro-Don, 800/829-0687,
To keep glazing putty from sticking to my fingers, I dust them
with a light coating of plaster of Paris. Starting at a corner
and holding a ball of putty in one hand, I tear off thumb-sized
chunks and press them roughly in place with my fingers (Figure
3). When one side of the sash is fully loaded, I place the
clean knife blade in a corner and hold it at an angle steep
enough to ensure that the edge of the putty won't be visible
from the other side. Then, using pressure from my forefinger to
hold the knife blade tight to the edge of the rebate, I draw
the blade smoothly from one side to the other.
Figure 3. Holding a ball of glazing putty
in one hand, a worker tears off manageable chunks and presses
them in place with her fingers (top). When one side of the sash
is fully loaded, she tools the compound smooth with a glazier's
curved putty knife (bottom).
To ensure that the putty stays smooth and doesn't pull out, the
knife should be absolutely clean and free of pits. I've found
that a light spritz of WD40 also helps.
After trimming away the excess putty, I roll it back into the
ball and move on to another section. When all the sash have
been reglazed, I set them aside to cure for a few days. The
glazing compound I use skins over enough to accept primer in as
little as 24 hours, but the longer drying time means fewer
brush marks in the still-soft putty.
I put a second coat of primer on the exterior faces and follow
that with a coat of paint.
The easy way to make antique windows more energy-efficient is
to add storm windows. Lots of low-profile storms are available
these days that can be installed from the inside or the
outside. I've also had good luck retrofitting sash with weather
stripping. Instead of the spring bronze systems that are a
nightmare to install, I use an assortment of silicone beads and
nylon pyle (brush-type) weather seals; they snap into narrow
grooves that I rout into the surfaces of the sash with a
specially designed slot-cutting bit (Figure 4).
Figure 4. The author prepares a sash to
receive weather stripping by routing a 3mm groove into the
mating surfaces of the sashes (top). After the sash is fully
primed, horizontal surfaces — such as the meeting rail
shown above — are fitted with silicone bead. On the
exterior of each sash, vertical surfaces are fitted with
brush-type weather seals, which seal tightly to the stops but
don't interfere with opening and closing.
All these products are sold by Resource Conservation Technology
Restringing the Sashes
Unless a client specifically asks me to fix the top sash in
place, I prefer to make both sash operable. This feature is
particularly welcome on cool summer nights, when opening both
halves allows the air to circulate freely.
Whether I'm restringing both sash or just the bottom, the
procedure is the same. I open the covers that allow access to
the weight boxes and cut the old cord from the sash weights. If
the weights are missing, I weigh the sash with a hand-held
fishing scale, then divide by 2 to determine the correct
replacement size (old window weights are usually coded at the
top with Roman numerals, so a 6-pound weight would be marked
I fish the new cord through the pulley by attaching it to a
5-foot length of string with a lead fishing weight on the end
(Figure 5). Sash cord is available in a variety of sizes and
strengths; for residential windows, the stuff I use is rated
for a working load of 94 pounds.
Figure 5. A weighted string helps the
author fish new sash cord over the pulley and down to the
bottom of the weight box (left). He secures the cord to the
sash weight with two half-hitches, then captures the excess
cord with a hog ring to prevent it from ever getting snagged in
the cavity (center). To allow plenty of slack for attaching
cord to sash, he pulls the weight to the top of the cavity and
clamps the cord (right).
I loop the cord through the hole in the weight and tie it with
two half-hitches, leaving a few inches of slack pointing
upward. To prevent any future snags, I crimp the loose end back
onto the cord using a hog ring. Next I pull the cords as high
as they'll go and secure them with a spring clamp. Placing each
sash in turn at the bottom of the jamb, I cut the cord about an
inch below the knot mortise in the edge of the sash and tie it
in a simple overhand loop. When both sides are done, I remove
the clamps and operate the sash to make sure it enjoys full
range of motion. If the weights bottom out or catch on the
pulleys, I retie the cords and try again.
Once I'm satisfied with the length of the cords, I secure each
to the sash with two copper roofing nails — one through
the knot, the other about two inches above the first.
Before fastening the cords to the lower sash, I temporarily
remove the sash so that I can replace the box covers and the
parting bead. I secure the parting bead with 1 1/2-inch
hardwood trim nails (Maze Nails, 800/435-5949,
www.mazenails.com) spaced approximately 24 inches apart. If
there's a noticeable gap between the bead and the frame, I
cover it with a light bead of caulk.
Next, I replace the stops. First I make sure that any paint on
their inner edges has been scraped off. Then I hold each one
snugly against the bottom sash and tack it with the same nails
I used for the parting bead. I don't drive the nails home until
I'm satisfied that the window operates as smoothly as any
modern unit (Figure 6).
Figure 6. A restored double-hung's
authentic divided lights and period glass are visible even
behind a storm window. With occasional maintenance, this unit
should serve faithfully for another century.
After all the stops are in place, I rub a block of paraffin wax
along the channels of the window frame to provide
lubrication.Dixon Kerr is a restoration contractor in
Richmond, Va., and the co-founder of the Alliance to Conserve
Old Richmond Neighborhoods.