Repairs to wooden windows are usually labor intensive and relatively
uncomplicated. On small scale projects this allows the do-it-yourselfer
to save money by repairing all or part of the windows. On larger
projects it presents the opportunity for time and money which
might otherwise be spent on the removal and replacement of existing
windows, to be spent on repairs, subsequently saving all or
part of the material cost of new window units. Regardless of
the actual costs, or who performs the work, the evaluation process
described earlier will provide the knowledge from which to specify
an appropriate work program, establish the work element priorities,
and identify the level of skill needed by the labor force.
The routine maintenance required to upgrade a window to "like
new" condition normally includes the following steps:
- some degree of interior and exterior paint removal,
- removal and repair of sash (including reglazing where
- repairs to the frame,
- weatherstripping and reinstallation of the sash, and
These operations are illustrated for a typical double-hung
wooden window, but they may be adapted to other window types
and styles as applicable.
Historic windows have usually acquired many layers of paint
over time. Removal of excess layers or peeling and flaking paint
will facilitate operation of the window and restore the clarity
of the original detailing. Some degree of paint removal is also
necessary as a first step in the proper surface preparation
for subsequent refinishing (if paint color analysis is desired,
it should be conducted prior to the onset of the paint removal).
There are several safe and effective techniques for removing
paint from wood, depending on the amount of paint to be removed.
Paint removal should begin on the interior frames, being careful
to remove the paint from the interior stop and the parting bead,
particularly along the seam where these stops meet the jamb.
This can be accomplished by running a utility knife along the
length of the seam, breaking the paint bond. It will then be
much easier to remove the stop, the parting bead and the sash.
The interior stop may be initially loosened from the sash side
to avoid visible scarring of the wood and then gradually pried
loose using a pair of putty knives, working up and down the
stop in small increments. With the stop removed, the lower or
interior sash may be withdrawn.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 the parting bead which holds it in place is set into a groove
in the center of the stile and is thinner and more delicate
than the interior stop. 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. The upper sash can
be removed in the same manner as the lower one and both sash
taken to a convenient work area (in order to remove the sash
the interior stop and parting bead need only be removed from
one side of the window). Window openings can be covered with
polyethylene sheets or plywood sheathing while the sash are
out for repair.
The sash can be stripped of paint using appropriate techniques,
but if any heat treatment is used, the glass should be removed
or protected from the sudden temperature change which can cause
breakage. An overlay of aluminum foil on gypsum board or asbestos
can protect the glass from such rapid temperature change. It
is important to protect the glass because it may be historic
and often adds character to the window.
Deteriorated putty should be removed manually, taking care
not to damage the wood along the rabbet. If the glass is to
be removed, the glazing points which hold the glass in place
can be extracted and the panes numbered and removed for cleaning
and reuse in the same openings.
With the glass panes out, the remaining putty can be removed
and the sash can be sanded, patched, and primed with a preservative
primer. Hardened putty in the rabbets may be softened by heating
with a soldering iron at the point of removal. Putty remaining
on the glass may be softened by soaking the panes in linseed
oil, and then removed with less risk of breaking the glass.
Before reinstalling the glass, a bead of glazing compound
or linseed oil putty should be laid around the rabbet to cushion
and seal the glass. Glazing compound should only be used on
wood which has been brushed with linseed oil and primed with
an oil based primer or paint. The pane is then pressed into
place and the glazing points are pushed into the wood around
the perimeter of the pane.
The final glazing compound or putty is applied and beveled
to complete the seal. The sash can be refinished as desired
on the inside and painted on the outside as soon as a "skin"
has formed on the putty, usually in 2 or 3 days.
Exterior paint should cover the beveled glazing compound or
putty and lap over onto the glass slightly to complete a weather-tight
seal. After the proper curing times have elapsed for paint and
putty, the sash will be ready for reinstallation.
While the sash are out of the frame, the condition of the
wood in the jamb and sill can be evaluated. Repair and refinishing
of the frame may proceed concurrently with repairs to the sash,
taking advantage of the curing times for the paints and putty
used on the sash. One of the most common work items is the replacement
of the sash cords with new rope cords or with chains. The weight
pocket is frequently accessible through a door on the face of
the frame near the sill, but if no door exists, the trim on
the interior face may be removed for access. Sash weights may
be increased for easier window operation by elderly or handicapped
persons. Additional repairs to the frame and sash may include
consolidation or replacement of deteriorated wood. Techniques
for these repairs are discussed in the following sections.
The operations just discussed summarize the efforts necessary
to restore a window with minor deterioration to "like new"
condition. The techniques can be applied by an unskilled person
with minimal training and experience. To demonstrate the practicality
of this approach, and photograph it, a Technical Preservation
Services staff member repaired a wooden double-hung, two-over-two
window which had been in service over ninety years. The wood
was structurally sound but the window had one broken pane, many
layers of paint, broken sash cords and inadequate, worn-out
The staff member found that the frame could be stripped of
paint and the sash removed quite easily. Paint, putty and glass
removal required about one hour for each sash, and the reglazing
of both sash was accomplished in about one hour. Weatherstripping
of the sash and frame, replacement of the sash cords and reinstallation
of the sash, parting bead, and stop required an hour and a half.
These times refer only to individual operations; the entire
process took several days due to the drying and curing times
for putty, primer, and paint, however, work on other window
units could have been in progress during these lag times.