|
Historic
House Restoration:
Tips on Window Repair
By: Kim Davis (Old North
Knoxville webmaster)
June 1, 2003
Hang on to those old windows! Did
you know that old windows, in combination with good storm windows and
exterior caulking, are just as energy efficient as new windows?
Also, they are a better investment. Even though they may require
some maintenance, they will never require complete replacement as all
replacement windows will. Replacement windows are not an investment
that will last another lifetime the way the old windows already did,
because they are made of
- Springs that will lose their spring
- Strings that will break
- Plastic things that will fatigue and
crack, and
- Double paned glass that will fail and
cloud.
Here are some tips on repairing pre-1945
rope and pulley windows, as related by David Liberty, owner of windowrepair.com.
David is well known in the Boston area for his work over the past twenty
years restoring historic windows. See his article on the This
Old House website.
The basic parts of old double-hung windows are shown in the drawing to the
right. Many of the repairs to these types of windows include:
replacing the broken ropes that anchor the window sashes to the iron
weights, rotten or cracked frame rail on the bottom sash, and reglazing of
the window panes.
First of all, here is a list of the stuff
you may need to perform various tasks related to disassembling the window
and repairing it:
Disassembly of the window
In order to inspect the window to see
what needs to be done, you will need to remove one or both of the
sashes. Often the first step is freeing a window sash that has been
painted shut by layers of paint over the years. This is done with
either a utility knife, or the handy tool at the right called a window
zipper. This tool, along with other tools discussed in this article,
may be purchased at specialty hardware stores or at the Boston
Building Materials Cooperative (BBMC). Another fancier option is the Fein
Multi-Master, a multi-purpose tool for sanding, scraping, sawing,
rasping, cutting, slicing, and grout removal ($180 on amazon.com).
The first step in removing the lower (or
interior) sash is to
take off both of the window stops. Working from the bottom to the
top in small increments, use the flat bar shown to the left and putty
knives to delicately pry off the stops from the edge facing away from the
house interior to avoid
visible scarring of the wood. Place the blade of the putty knife in
the seam and tap the knife with a hammer until you can work the trim
free. Pry out the bottom first because the top of the stop is
fragile. On fancier, 19th century windows, the top of the stop may
be notched in order to interlock into the top of the window. Let the
middle of the stop bow out, letting the top stay hooked, then pull out the
bottom first. With the stops removed, the lower sash
may be withdrawn. The sash cords should be detached from the sides of the
sash and their ends may be pinned with a nail or tied in a knot to prevent
them from falling into the weight pocket.
Removal of the upper sash on double-hung
units is similar but requires removal of the parting bead which holds it
in place. Even thinner and more delicate than the stop, it is set
into a groove in the center of the stile. After removing any paint
along the seam, the parting bead should be carefully pried out and worked
free in the same manner as the interior stop, using a small hammer and a
chisel-bladed paint scraper.
Stabilization of deteriorated windows
With the sashes out of the frame, the
condition of the wood may be evaluated. The bottom rail of the
interior sash is usually the part of the window that has been subjected to
the most abuse over the years. If it is just cracked, and doesn't
move around, then the holes may be filled with epoxy or Minwax wood
putty. For bigger cracks and holes, more intricate reforming of edges
and better longevity, use the slower drying epoxy available from Abatron.
For smaller cracks and holes, the Minwax
wood filler is okay, which can be sanded out immediately, but cannot
be restained to match the existing wood (it must be painted).
Another product that has come to our attention recently is Architectural
Epoxy, sold by Advanced Repair Technology.
If the
wood is too far gone to repair, then take the sash to a custom millworker.
Most millwork firms can duplicate parts, such as muntins, bottom rails, or
sills, which can then be incorporated into the existing window. Some possible sources for this service include Nolen Products, Inc.
and High Oaks
Construction in Knoxville.
Cracked, deteriorating putty around the
glass panes can be removed manually, taking care not to damage the wood
along the rabbet. However,
it is very difficult to get all the old putty out without breaking the
glass. Heat may be used to get the last remnants out, but David
recommends putting a piece of masonite on the glass to protect it.
If the glass does break, reproduction wavy glass is available from Bendheim,
but it is very expensive. To do a reglazing job properly,
David recommends using acrylic glazing, not putty, because it doesn't
crack and get rock hard. Advanced Repair Technology
manufactures an acrylic glazing called Glaze-Ease. The metal points
hold the glass in place while the glazing hardens, which takes about one
month. One big reason to let a "professional" do the
reglazing job is that it is very difficult to get a proper sightline – one is not supposed to see the
glazing when looking out the window. Finally, David cautions against
using "dip stripper" services that use caustic soda to remove
old putty due to the possible permanent harm to the wood frame.
Another tool to avoid is the Prazi
Putty Chaser. According to David, the tool spews dust (bad if
removing old lead paint) and may damage the wood.
To avoid all the heartache of possibly
damaging the windows during putty removal, glass removal, then glass
replacement and glazing, David recommends just taking the sash to a good
glass shop and letting them do it. I hear that a good local service
for this is Keith Window Company at 2501 North Central Street
(865-524-2424).
Replacement of sash cords
The "weight port" may be
accessed by removing the cover on the bottom of the window secured by a
single screw. Although sash "spot" cord is still available as a
replacement, David actually prefers copper-dipped steel chain because of
its ease of installation and longevity. The chain and other historic
window hardware discussed in this article are available by calling The
Architectural Resource Center. One box of chain costs about $35-40
and does six windows.
If you carefully tilt the window sash and
examine the sides, you'll see a long groove with a round hole at the
bottom (the "blind knot hole"). That's where the cord is knotted
and secured to the window, and is one of the  vulnerable
spots where sash cord commonly breaks (the other is where the cord flexes
through the pulley). Instead of knots, the chain is secured to the
sash using a spring fixture. Click here
to see a closeup of the chain attached to the sash with the
spring. Use a 1" drywall screw through the hole in the
middle of the spring to hold it in place.
The chain is held to symmetrical
weights (the most common) by a loop fixture. Click here
to see a closeup of the chain attached to a weight. Less
common are asymmetrical weights. These types of weights are
attached to the chain with another spring fixture. The bottom line
is, you want to have the weight hanging straight.
Now that we know how to attach the chain
to the sash and the weight, the procedure to get the proper chain length
for final assembly is as follows. First, feed the chain through the
pulley with the flat end of the chain facing down. After passing it
through the pulley, attach the chain to the weight, and with the weight
sitting on the bottom of the weight port, take hold of the chain where it
exits the pulley. This is where the spring fixture is
attached. When all put together, the weight is nearly at the
bottom. Before putting it all together though, you may want to
consider weatherstripping the window, explained in the next section.
Remember that in six over one windows,
the single pane sash weighs more -- therefore it will have bigger
weights. One weight is one half the weight of the sash. If the
window flies up, it is overweighted, meaning that the glass has probably
been replaced. Likewise, if the window floats down, it is
underweighted.
Installation of weather stripping
|
|
 |
Above, David Liberty cuts the correct length of weather- stripping.
|
So what about the supposed problems with
heat insulation in old windows, you ask? Surprisingly, only about 10% of
the total household heat loss occurs through the glass of properly
maintained historic windows. With the addition of storm windows, this
figure is likely to be even less. To achieve a tighter fit easily, David
recommends installing "spring bronze" weather stripping (called Bronzegard,
available at the
BBMC) between the window
sashes and the stops, a process that takes just a few minutes with tin
snips and a Dual-Fast™ power stapler available at Home Depot. Once
completed, the new weather stripping eliminates rattles, drafts, and
noise, but best of all, allows homeowners to enjoy the beautiful sunlight
streaming through the original wavy old glass without feeling horribly
guilty about being energy pigs.
|
|
|
This is what the
weather stripping looks like before attached. Note the notch for the pulley area.
|
Only install the weatherstripping next to
the areas where the sash contacts the sides of the window, using tinsnips
to trim it around the pulley area on the upper sash. When stapling
the weather stripping, put the first two staples 1/3 down from the top and
1/3 up from the bottom to commit to the alignment. Don't jam the weather
stripping up the edge of the window, in order to leave a little
wiggle room. Staple every two inches or so, and when finished, run a
paint scraper down the score line to give it a little
"puffiness" to create better compression. Click here
to see a closeup of the installed weather stripping. Apply a little Liquid
Gold if the reassembled window has problems with the sashes sticking.
Closing comments
Having been in this business for 20
years, David feels very strongly about going the extra mile to repair
original historic windows, which he feels have superior performance,
durability and beauty over new wooden replacement windows. Although new
windows may work well initially, David has personally observed that it is
only a matter of time before the farm-grown sugar pine construction rots,
the seals in the double paned glass fail causing condensation to form
between the panes, and the spring-loaded jamb liners, plastic parts and
insulating foam degrade to non-working status. Consider this interesting
factoid: David notes that wealthy purists around Boston spend upwards of
$7000 per window to completely reproduce custom windows with the pre-1945
rope and pulley design, using salvaged wood from river bottoms, historic
glass panes and hand-made pulley systems with iron weights! He urges
owners of historic homes to hold on to their original windows with the
strong, tight-grained wood, not only because of their nearly irreplaceable
quality, but also because they are quite easy to repair in a
cost-effective manner.
Need help with restoring your old windows? Contact Sam
Soemardi of Asheville Window Restoration at
828 275 8804 or .
Another good website to read about the
procedures discussed above is at http://www.oldhouseweb.com/stories/Detailed/169.shtml
|
