A few months ago I received a call from a prospective client
who wanted to replace the casement windows in her home in
Berkeley, Calif. I went over there thinking it would be a
straightforward replacement. As soon as I saw the house, I
could tell that replacing the windows would be a very difficult
job. The yard was beautifully landscaped, and the 1920s Spanish
Mediterranean home was in pristine condition.
Replacing the windows would require us to remove the interior
trim and break out a lot of heavily textured stucco. Demolition
would create a terrible mess, and it would be nearly impossible
to patch this particular type of stucco without it showing (see
Figure 1). Even if we could patch the stucco, there was the
question of what kind of windows to install. Wood or painted
fiberglass windows would look right, but they would have to be
custom made to fit nonstandard openings.
Figure 1.Replacing this window would require
tearing out stucco, and it would be nearly impossible to blend
a patch into such a highly textured surface.
The usual approach would be to use vinyl windows because it's
easy and doesn't cost much to get them in custom sizes. It's
even possible to get them as retrofit units that fit inside the
existing jamb, but, retrofit units or anything made out of
vinyl would destroy the architectural character of this
Because the conventional choices didn't seem to fit, I asked
the client what she disliked about the old windows. She liked
the way they looked, but the house was on a busy corner, and
the early morning commuters woke her up every day at 5 a.m. In
addition, the house was drafty and the heat was uneven. We
discussed the options and decided to rehabilitate the existing
We could have replaced the single-pane glazing with insulated
glass, but the owner decided against it because she liked the
wavy look of the original glass. Heat loss was not a big
concern because the house was in an area where frost is rare
and almost no one needs air conditioning.
The windows were old-fashioned casements with butt hinges.
Most of the sash were in excellent condition, but several had
enough rot that they needed to be replaced. My window supplier
agreed to fabricate the replacement sash and showed me a sample
unit. The existing windows had compressible brass
weatherstripping, the kind that's fastened to the inside of the
jamb with dozens of nails. It fit poorly and made some of the
windows difficult to open and close.
Material of choice. The
sample unit had modern foam-polyethylene weatherstripping set
into a kerf around the perimeter of the sash. I told the
supplier that we'd like to put the same kind of
weatherstripping on the remaining windows, and he agreed to
sell me everything my carpenters needed to do the job. He
provided us with a three-wing router bit (Figure 2) and a roll
of Q-Lon QEZD-250 weatherstripping (Figure 3).
Figure 2.A bearing-over metric-sized bit is used
to cut kerfs for the weatherstripping.
Figure 3.The material on the left is the QEZD-250,
which the author used on the windows. The larger piece on the
right is a similar product commonly used on doors.
This material is similar to the kerf-applied weatherstripping
that comes on many prehung exterior doors. But instead of
compressing between the stop and face of the door, it fits
between the jamb and the edge of the sash. Q-Lon (Schlegel
Systems, Rochester, N.Y.; 585/427-7200,
www.schlegel.com) consists of a stiff
plastic fin and urethane foam with a polyethylene cladding. The
profile we used had flexible barbs to keep the fin in the
Reworking the Sash
The client was living in the house, and some family members
were extremely sensitive to dust. Since one of the reasons for
rehabbing the windows was to avoid making a big mess, we
covered the patio with drop cloths and set up a work table
The gap around the existing windows was too small for the new
weatherstripping. We needed about 1/8 inch to get it in, and
our first thought was to pull the sash and use a portable table
saw to rip material off each edge. There was paint buildup,
however, and the house had settled so that in some places the
sash rubbed and in others the gap was fine. We dealt with that
by scribing the sash about 1/8 inch in from the jamb. Once the
sash were marked, we removed them and took off all the
hardware. We used a power planer to trim the sash to size
(Figure 4). The edges were covered with lead-based paint, so we
connected the planer to a dust-collecting vacuum. Very little
debris made its way onto the drop cloth.
Figure 4.We used a power planer to refit the sash
to the openings. The vacuum and dust collection hose captured
nearly all of the chips.
The fin is designed to fit into a kerf, so the next thing we
did was use a router and three-wing cutter to cut a slot on
each edge of the sash about 3/8 inch in from the outside face.
It's important to use the right-size bit. If the kerf is too
narrow, the fin won't go in; if it's too wide, the weatherstrip
won't stay in place. Our supplier made sure we had the correct
2-mm (.078-inch) bit to make the cut (Figure 5).
Figure 5.The slots for the weatherstripping were
cut along the edge of the sash just in from the outside
Next, we used scissors to cut the weatherstripping to length
and miter the ends so it would wrap the sash like a casing
wraps a picture-framed window (Figure 6).
Figure 6.The pieces of weatherstrip are snipped to
form mitered corners.
The last step was to press the fin into the slot (Figure 7).
There were some gaps in the seal because the kerf-applied
material could not run through the hinges. It's not a big issue
in our climate, but if we were in a colder area, I would have
made the seal continuous by running a strip of self-adhesive
foam across the hinge leaf on the sash.
Figure 7.The weatherstrip is pressed into the kerf
and held in place by barbs on the fin. This piece will be
removed when it's time to paint the edge of the
The openings needed work, too. We removed the original
weatherstripping, filled all the nail holes, and gave the
surface a coat of primer and paint. The new weatherstripping
could be pulled back out of the slot, which was good because we
had to test-fit the first couple of sash. Once we understood
the tolerances, we were able to process several windows at a
Some of the sash had dings and small areas of rot, so the
carpenters patched them with wood filler. We also patched the
insides of the jambs and then primed and repainted the jambs
and edges of the sash (Figure 8). Reinstalling the windows was
simply a matter of putting the hardware back on and screwing
the hinges to the sash.
Figure 8.The new weatherstripping is unobtrusive
but significantly cuts down on the amount of air and sound that
comes through this window.
We used a similar weatherstripping product on the existing
doors. It came attached to a removable stop, which we fastened
over the existing stops. The door material can also be
installed in a kerf between the stop and the jamb, but the kerf
would have to be made before the jamb was assembled, so it
wouldn't work on a retrofit.
Cost and Results
You can find kerf-applied weatherstripping at a good
lumberyard or building supply house, but you will probably have
to special order the particular profile that we used. The
material we bought was white, but it's also available in cocoa,
black, stone, bronze, and beige. Depending on where you buy and
how much you get, you could pay between 25¢ and
75¢ per foot — we paid around 50¢ per
foot. The cost of the material hardly mattered because
rehabbing the windows was way less expensive than replacing
The first couple of windows were slow going, but once we got
up and rolling, it took maybe two hours, including painting, to
do each opening. The client was very happy with the results. It
didn't cost a fortune, and we didn't have to tear up the house.
The owner can still hear the traffic, but now it's background
noise. The house is less drafty and feels warmer. We could have
made more money replacing the windows, but this project paid
off by giving us a satisfied customer who has since since been
referring us to her friends.
David Grubbis a remodeling contractor in Berkeley,