NEW HAMPSHIRE DIVISION OF HISTORICAL RESOURCES
State of New Hampshire, Department of Cultural Resources 603-271-3483
19 Pillsbury Street, 2nd floor, Concord NH 03301-3570 603-271-3558
Voice/ TDD ACCESS: RELAY NH 1-800-735-2964 FAX 603-271-3433
HISTORIC WOODEN WINDOWS
JAMES L. GARVIN
NEW HAMPSHIRE DIVISION OF HISTORICAL RESOURCES
THE WINDOW SASH AS A CHARACTER-DEFINING ELEMENT OF A BUILDING
Few elements of a building contribute more to its architectural character than do the window
sashes. The character of the sash is obvious from the exterior even when (as was often the case)
its exterior face was painted black or another dark color. There is a great difference between a
window opening filled with twelve-over-eight sashes and one filled with two-over-two sashes.
The character of the sash is even stronger from within the building, where the grid of muntins
interposes itself between the eye and the view from the window. The inner faces of the muntins
are moulded, and the profiles of these mouldings evolved over time, contributing much to the
expression of style or period in a structure. As indicated on the accompanying chart, the muntin
profile provides a useful means of dating a building as well as helping to define the aesthetics of
the window and the room.
Yet sashes are meant to be looked through. It is easy to look past the grid of muntins and to
ignore their beauty and the size and character of the glass. Perhaps because sashes are largely
transparent, they are often undervalued as a contributing element to the style and character of a
building. People often assume that all old windows are much alike, or that the character of the
sash is unimportant. Coupled with the common idea that old sashes are loose, fragile and drafty,
the assumption that they are insignificant makes the sash the most vulnerable and often-replaced
element of a historic building.
In fact, the character of the sash has always been integral to the style of the building. While that
fact may have been missed by the owner of a building, it was not lost on the architect or joiner
(finish carpenter). In compiling the first American builder’s guidebook, The Country Builder’s
Assistant (1797), joiner Asher Benjamin signaled his break with the eighteenth century by
illustrating three new muntin profiles that were appropriate for the incoming federal style of
architecture. As shown in the accompanying chart, new sash designs appeared every ten or
fifteen years during the nineteenth century, lending their character to succeeding architectural
Any historic building with its original sashes and glazing therefore retains a higher degree of
architectural integrity than a comparable structure in which the sashes have been replaced.
Where original sashes survive, their preservation should be a paramount concern of the
A BRIEF HISTORY OF THE WOODEN WINDOW SASH
The sliding window sash was introduced into the British colonies of North America just after
1700. Prior to that time, window openings had been filled with casements. Casements are
sashes that are hinged on their sides to open outward. The lights or panes of glass in casement
sashes, called “quarrels,” were usually small and diamond-shaped. The quarrels were held within
a latticework of lead members, called “cames,” which have an H-shaped cross section. To
stiffen the somewhat flexible assemblage of cames and quarrels, a few wooden sticks were
placed across the sashes between the outer stiles of the casements, and the lead was wired to
these stiffeners at intervals.
The sliding sash first appears in written records in Boston and Philadelphia just after 1700.
Some sliding sashes were apparently filled with leaded glass, but most were glazed with square
lights of glass held within a grid of moulded wooden members called “muntins.”
The accompanying chart shows the profile or cross sectional shape of the earliest muntins. This
profile remained relatively unchanged until near the end of the eighteenth century, although
every joiner had his own set of tools and different sets of sash moulding planes were seldom
exactly alike. Thus, there is some variation in this early cross-sectional profile and all later
muntin profiles. This variation diminished when machine-made sashes were introduced in the
latter half of nineteenth century.
The eighteenth-century muntin was heavy and thick, interposing a strong grid between the
occupant of a room and the outdoors. Because of the high cost large sheets of early glass, panes
were usually small (often 7 by 9 inches or 8 by 10 inches). The proportion of wood to glass in
early sashes was quite high, and tended to diminish through the nineteenth century as larger glass
sizes and thinner muntin profiles were progressively introduced.
For the most part, eighteenth-century window sashes were not counterbalanced by weights. The
upper sashes in a pair were usually fixed in place, being supported by strips of wood placed
below their sides in the window openings. Only the lower sashes could open. They slid up and
down between the strips of wood that supported the upper sashes and similar strips of wood,
called “sash stops,” that were nailed against the sides of the window frames. The lower sashes
slid upward against the inner faces of the fixed upper sashes and the sash stops; the latter created
a groove or channel that restrained and guided the moving sash.
EVOLUTION OF WINDOW MUNTIN PROFILES
IN NEW ENGLAND
1705 TO THE PRESENT
(The profiles shown below are derived from dated buildings. Some profiles may
occasionally persist beyond the end of the usual date range as shown in the chart.)
1705 1790 1795 1830 1835 1835 1845 1880 1880
to to to to to to to to to
1790 1830 1850 1850 1860 1870 1880 1900 present
Because sashes were usually not counterbalanced, they were held open, or partly open, by sticks
or other props placed beneath them, or by spring catches of various designs attached to their side
members or stiles.
Occasionally one will encounter an extraordinary eighteenth-century dwelling in which the
movable lower window sashes were counterbalanced by weights that are attached to the sashes
by cords. These cords run over a wooden sheave set into the tops of the side frames of the
windows, allowing the weights to rise and fall in pockets on each side of the window opening.
Such early weights are almost always found to be of cast lead. In contrast to later cast iron
window weights, which are usually round in cross-section, older lead window weights were
usually square or rectangular in cross-section.
These rare counterbalanced windows of the eighteenth century gave rise to the common doublehung
windows of the latter part of the nineteenth, described below.
EVOLUTION OF MUNTIN PROFILES IN WOODEN SASHES
The earliest sliding sashes, introduced to North America shortly after 1700, had heavy muntins
that were often over an inch in width. These muntins were often relatively shallow in relation to
their width, so the sashes were not excessively thick. The considerable width of the muntins,
however, combined with the tendency to use small lights of glass in these early windows, gave
eighteenth-century sashes a heavy appearance that is quite noticeable from inside or outside a
Although there is no hiding the heavy grid of muntins in early sashes when seen from within a
building, painters often took steps to diminish the effect of heavy sash bars and small lights of
glass as seen from the outside. Records make it clear that the outside faces of such windows
were often painted black, clearly in an attempt to disguise the heavy grid of bars against the dark
void of the room within. This practice continued throughout the nineteenth century, although in
Victorian times sashes might be painted dark red or green or some other color that contrasted yet
harmonized with the color of the exterior window casings and of the body of the building.
Photographic evidence from the 1840s onward shows, however, that exterior window casings
were often painted white, often in contrast to unpainted clapboards or to clapboards painted with
inexpensive red or yellow ochre. In such cases, the outside faces of sashes were often painted
white as well. Thus, two contrasting approaches to the exterior treatment of multi-paned
sashes—one intended to hide the sash bars and one to emphasize them—flourished
simultaneously during the 1700s and early 1800s.
The evolution of the muntin profile after the end of the eighteenth century was generally one of
increasing delicacy. At the same time, production of window glass in the United States reduced
the cost of glazing and permitted sashes to have fewer but larger lights. Thus, window openings
tended to become larger, sashes became lighter and held larger panes, and interiors generally
became brighter. This increasing illumination was characteristic not only of rooms, but also of
entries or stairhalls. The late 1700s saw the introduction of fanlights in doorways or
“frontispieces.” After 1800, these windows became larger, often taking the form of a wide semiellipse.
Sidelights flanking doors also became popular at this time, and fanlights often spanned
not only the door opening but also the sidelights on each side of the door. In contrast to the dark
entries of the 1700s, in which a small transom sash above the door was the only illumination
provided, this new fashion filled hallways with light.
The advent of the federal style in the late 1700s and early 1800s was accompanied by several
patterns of window muntin. The most common type, popular until about 1830, was nearly
identical in profile to the heavy muntin of the 1700s, but was smaller in dimension. Its profile
consists of quarter-round mouldings and flat fillets. Another muntin type first seen just before
1800 had a cove-and-bead profile. Generally restricted to more expensive buildings or urban
areas, this profile is much less common than the traditional quarter-round-and-fillet pattern.
The quarter-round-and-fillet pattern did not disappear with the advent of the Greek Revival style
in the 1830s. Instead, it evolved, adopting an elliptical moulding in place of the quarter-round.
The Greek Revival style was, however, accompanied by alternate muntin profiles that were
noticeably different from those seen earlier. Perhaps the most distinctive was the flat, angular
profile. Like some mouldings seen in Greek Revival joinery, this muntin relies on its faceted
surfaces rather than on curves for its character. This type of muntin is often seen in conjunction
with woodwork that is similarly decorated with flat surfaces rather than with curved mouldings.
Also popular during the Greek Revival period, as well as in buildings of a Gothic character, is
the Gothic muntin. Often assuming the profile of a rounded or pointed arch, this simple muntin
appeared in the late 1830s and persisted from the 1840s through the 1860s.
A profile that enjoyed nearly the longevity of some of the older quarter-round-and-fillet shapes
was the sharp ogee muntin. Composed of S-curved mouldings that meet in a knife edge, this was
the sharpest and thinnest profile ever used in American windows. First seen in the late Greek
Revival buildings of the 1850s, the sharp ogee muntin persisted up to the turn of the twentieth
century, appearing in six-light sashes in the earlier years and in two-light sashes at the end of the
century. When used in large sashes, as in churches or public buildings, this muntin profile is
usually given added depth to compensate for its inherent weakness in the face of the wind
pressures that larger windows must resist.
Another muntin profile that has enjoyed a popularity rivaling that of the earliest quarter-roundand-
fillet muntins is still in use today. This is the ogee-and-fillet profile, first seen in early
colonial revival buildings. Having a strong cross-section, this profile came into its own as twoover-
two sashes became popular in the late 1800s. The shallow ogee or S-curved moulding of
this muntin bears a superficial resemblance of the early quarter-round-and-fillet designs, making
the new profile ideal for buildings in the colonial style or for use with any other architectural
style. The profile is often seen in modern windows with true divided lights, and is most
commonly encountered in the ever-popular Brosco “Boston” sashes, available in configurations
ranging from two lights to multiple lights.
Because window sashes are fragile and easily damaged by neglect, they frequently deteriorate
more quickly than other elements of a building. Because they strongly reflect the architectural
style of a given period, sashes were often replaced during remodeling even if they had not
deteriorated beyond usefulness. Thus, it is not unusual to find old buildings with sashes that are
much later in date and style than the majority of other architectural features.
In such cases, it is often of great interest to learn the original style of sash in a building. It will
often be found that a few original sashes were left in place in some out-of-the-way location.
Odd-sized windows in the back of the building, or attic windows too high up to catch the eye, are
often found to be the only survivors from an otherwise-complete renewal of sashes. Also likely
to survive are original sashes that are fixed in place and part of a larger architectural feature, or
sashes of a size that could not be replaced by stock units of a later period. Thus, transom sashes
above a doorway are among the most likely to escape replacement, as are elaborate arched sashes
from a Palladian window or a stair landing. One such relic from the original period of
construction is enough to indicate the earliest muntin profile of a building.
Older sash styles are seldom available in the retail trade. Almost every style of sash that has ever
been made, however, can be acquired on custom order from specialized sash factories or from
joiners who have revived the art making sashes by hand. Among the best-equipped custom
manufacturers of historic sash reproductions are Kim Doubleday of KSD Wood Products,
Penacook, New Hampshire, Littleton Millwork, Inc., of Littleton, New Hampshire, and the
Walter E. Phelps Company of Brattleboro, Vermont.
HOW WOODEN WINDOW SASHES WERE MADE BY HAND
A window sash is one of the most delicate and complex building components made by the joiner.
Each muntin is a thin piece of wood stock, moulded on one side and rabbeted on the other to
receive glass and putty. Each muntin must intersect and be fitted to other muntins and to the
outer stiles and rails of the sash. The stiles and rails, in turn, must be firmly mortised and
tenoned together at the corners in order to create a rigid frame. If the sash is counterbalanced,
recesses for the sash cords must be plowed into the sides of the unit.
Because the inside face of the muntin is moulded, the end of every horizontal muntin must be
coped and tenoned to fit against the moulded surface of every vertical muntin, or against the two
stiles on the sides of the sash. The two horizontal rails must be coped and tenoned to the sides of
the stiles at each corner of the sash. And each vertical muntin must be coped and tenoned to the
upper or lower rail of the sash. A six-light sash has twelve of these complex intersections; a
twelve-light sash has twenty.
Because the ends of intersecting sash members must be coped and tenoned, sash moulding
planes were sold in pairs. The principal plane cut the moulded inside face of the muntin, stile, or
rail. The sash coping plane shaped the coped joint at the ends of the members, cutting across the
end grain of a board before the board was ripped into thin muntin stock. After the coped joint
was cut, the board was sawn into thin strips that were transformed into muntins through the use
of the principal sash plane.
Because the making of a sash by hand is painstaking and delicate work, joiners of the 1700s or
early 1800s devised a fair method of charging for their labor. They billed a customer by the
number of “squares of sashes,” or openings for lights of glass, that they fabricated. The more
openings for glass that were required, the more expensive the joiner’s labor on the sash. Thus, a
pair of twelve-light sashes would be more expensive than a pair of six-light sashes for a given
window opening. Conversely, smaller panes of glass might be cheaper than larger panes, so the
ultimate cost of a pair of sashes depended both on the joiner’s work and on the cost of glass. As
larger panes of glass became cheaper, the cost of windows became cheaper, since the use of
larger panes meant fewer “squares of sashes” in each window unit and thus reduced the joiner’s
Throughout the eighteenth century and much of the nineteenth, the outer frames (the stiles and
rails) of window sashes were mortised and tenoned together at the corners and held by wooden
pegs or pins placed through each joint. In most cases, the muntins were simply tenoned into the
stiles and rails; due to their small dimensions, these tenons were not pinned. Likewise,
horizontal muntins were simply tenoned into the vertical muntins without pins or nails, with the
entire window assembly depending for its tightness on the pinned joints at the four corners.
Because an “open” or unglazed sash is made of thin members pinned together at only four
points, the entire unit is often slightly flexible until it is glazed. The insertion of glass and putty
stiffens the sash into a unit that may retain its rigidity through decades of use and thousands of
raisings and lowerings.
The type of glazier’s putty used throughout most of our history has been whiting or chalk
(calcium carbonate) mixed into a paste in linseed oil. Powdered white lead, which has a drying
effect on linseed oil, was often added to the mixture in small quantities to make the putty harden
more quickly in the sash and thus allow the unit to be primed with paint soon after glazing.
THE MANUFACTURE OF GLASS
Until after World War II, common window glass was made by three methods. Two of those
methods depended upon the skill of glassblowers, who made their product entirely by hand. The
third method, introduced around 1900, was the first to manufacture window glass partly by
machine. Thus, all window glass made before the turn of the twentieth century is a hand-made
product, virtually irreplaceable today under normal circumstances.
The first hand-manufacturing technique, most common in the eighteenth and early nineteenth
centuries, was the crown method. In this type of manufacture, the blower gathered a mass of
molten glass from the furnace on the end of his blowpipe. Blowing the glass into a large sphere,
the blower attached the bubble to an iron pontil rod and removed the blowpipe, creating a hole at
the point where the pipe had been attached. By repeatedly reheating and spinning the sphere, the
blower used centrifugal force to cause the glass to open up into a large disk called a “table” or
“crown.” When finished and cooled, a crown normally had a diameter of from four to six feet.
From this crown, variety of panes of glass could be cut. The center of the crown was thickened
at the point where the pontil had been attached. Called the “bull’s-eye,” this central boss was
normally re-melted. Occasionally, glass bull’s-eyes were used to glaze a transom sash over a
door, or were even substituted for the upper wooden panels of the door, introducing a bit of
daylight into a stairhall or entry.
Because of its method of manufacture, a light of crown glass is often slightly convex rather than
perfectly flat. Glaziers normally set such glass with the curve or crown outward, carefully
setting the pane in a bed of putty that compensated for the contour of the glass. Seen from the
outside, windows glazed with crown glass often reveal a visible bulge in each pane, as if the
glass were swelling outward from air pressure within the building.
The crown method of manufacturer produces a glass that is often exceedingly brilliant and
reflective, having been made without contact with any solid surface. Crown glass remained the
favorite type for fine window glazing well into the nineteenth century.
Crown glass is manufactured by the Blenko Glass Company, Inc., of Milton, West Virginia.
An alternate method of making window glass, called the cylinder method, was practiced
throughout the eighteenth and nineteenth centuries alongside the crown method. As its name
implies, cylinder glass was made from a cylinder instead of a disk. Like crown glass, cylinder
glass started with a heavy “gather” of molten glass—sometimes as much as thirty-five pounds—
on a blowpipe. The mass of glass was blown into a sphere, and the sphere was elongated into a
cylinder through repeated heating, blowing, and swinging of the blowpipe. Eventually, the
glassblower would produce a cylinder about ten inches in diameter and from four to five feet
long. Other craftsmen would then snap off the constricted end where the blowpipe had been
attached to the cylinder, would slit the cylinder along its length, and would flatten the glass into a
rectangular sheet on a hot table.
The cylinder method produced a larger single sheet of glass than did the crown method. Being
rectangular rather than circular, this sheet had less waste after being cut into lights. Yet, because
it was flattened against a surface, cylinder glass lacks the brilliant finish of air-cooled crown
glass, and may show wrinkles or inclusions. Even though it was flattened on a hot table, cylinder
glass usually retains a slight curve in each pane, just as crown glass retains a slight bulge.
Cylinder glass is manufactured by S. A. Bendheim Company, Inc., of Passaic, New Jersey.
The technique of making cylinder glass improved over time. Yet the size of a cylinder was
limited by the strength of the glassblower. A blower had to possess enormous strength,
endurance, and lung capacity to fashion a cylinder, especially a cylinder of double-thick window
glass. For this reason, hand-blown cylinders never attained a length of over five feet or a
diameter of greater than a foot.
By about 1900, machines began to be developed that could produce glass cylinders of immense
size. These machines employed vertical blowpipes with large flared ends that attached
themselves to pools of molten glass. Compressed air was fed through these pipes as motors
slowly raised their ends from the molten bath. A huge cylinder of glass was slowly drawn
upward, cooling as it rose.
In its final development, the mechanical blowing process could produce a glass cylinder up to
thirty inches in diameter and forty feet tall. The improvement of this process between 1900 and
1928 marked the end of hand-blown window glass in the United States. From the 1920s to the
present, all commercially-sold American window glass has been manufactured mechanically,
either by the cylinder method or by more recent means of producing flat sheets, losing the
element of craft that had long marked the process.
For this reason, those buildings that retain old sashes and old glass are doubly rare. Hand-made
window glass, so easily overlooked and so easily broken, is the most fragile architectural legacy
we have from the eighteenth and nineteenth centuries. Both the sashes and their glazing embody
complex craft skills and warrant every effort at their protection and preservation.
Most eighteenth- and early-nineteenth-century windows have little or no hardware. Wooden
sashes of this period merely slide up and down in their grooves, being held open, or perhaps
wedged shut, by sticks placed under or above the movable lower sash.
Occasionally, one will find sashes that have small wrought iron hooks attached to the lower rails.
Staples fixed into the window stools permit the closed window to be hooked shut and locked.
As noted above, a few exceptional houses of the eighteenth century have counterbalanced lower
sashes, with cords that run from the movable sash over wooden sheaves in the upper side casings
of the windows. Lead weights descending in pockets outside the casings allow heavy sashes to
be lifted more easily.
This type of counterbalancing was becoming more commonplace by the early 1800s. In 1806,
Asher Benjamin illustrated counterbalances for both upper and lower sashes in his second
architectural guidebook, The American Builder’s Companion, thus prefiguring the double-hung
sash as it has remained in production and use until recent times. Yet such arrangements were
restricted to urban dwellings or the homes of the wealthy. Most dwellings did not have
counterbalanced sashes until after the mid-1800s.
As noted above, most windows of an earlier period were held open, or partially open, by props or
notched sticks of various designs. An alternative to such props was the window spring, a device
that attached to one of the stiles (side members) of the movable lower sash and snapped into
holes or notches cut into the window frame at various heights. Many types of window springs
were patented throughout the nineteenth century, and many types are still encountered on old
sashes. Probably the earliest pattern of window spring employed in New Hampshire was called
Kennedy’s patent. A number of New Hampshire joiners were licensed to use and sell this device
in 1803. According to its description, Kennedy’s spring “allowed one to raise and lower both the
upper and lower Sash, and by the assistance of Springs to support it at any height that is wished.”
By 1865, the Russell & Erwin Manufacturing Company of New Britain, Connecticut published
the first extensive American hardware catalogue, and this book illustrated no fewer than five
styles of window spring. Although window springs serve as locks when the window is closed,
the Russell & Erwin catalogue also listed sash locks in many designs, most of them intended to
be screwed to the upper and lower meeting rails in the same manner as modern helical sash
By 1865, too, the counterbalanced or double-hung sash had become commonplace. The Russell
& Erwin catalogue illustrated iron or bronze sash pulleys and cast iron sash weights that are
virtually indistinguishable from those used throughout the next century.
Most sash hardware of the nineteenth century was simple in design and rugged in construction.
Homeowners who are fortunate enough to retain such window fittings should make every effort
to preserve and use these easily-overlooked legacies from the past.
CASINGS, SHUTTERS, AND BLINDS
Although sashes are the principal element of a window, sashes are almost always accompanied
by inside and outside casings, and often by interior shutters and exterior blinds. Together, these
elements make up the full window unit.
Interior window casings almost always reflect door casings in the same rooms. Often as
distinctive as are the muntins in the sashes, window casings are important stylistic elements in
any room and are valuable as a means of dating a window. Because window sashes were more
often renewed than window casings, it is often easy to detect replacement of sashes when the
casings are of one style and the sashes are of a later style.
Sometimes the remodeling of a room was done with such thoroughness that both widow casings
and sashes were replaced. This is particularly commonplace during the Greek Revival period
from 1830 to 1850. The Greek Revival style required both window muntins and casings that
were distinctively different from those of the Georgian or federal styles. In order to maintain the
harmony of a remodeled room, the moulded casings of an earlier period were often supplanted
by flat casings when a room was modernized in the new Grecian style.
The same is true on the exterior. It is not unusual to find that an older house was updated with a
Greek Revival doorway or frontispiece. In such cases, the exterior window casings are often
found to have been replaced, at least on the front of the house, to harmonize with the character of
the new entrance.
Among the features that are often missing or damaged from eighteenth- or early-nineteenthcentury
windows are interior shutters. Often mistakenly called “Indian shutters,” these features
were intended to exclude the cold or to provide privacy in an age before window curtains were
common, not to defend a building against attack.
Interior shutters were made in three major types. The earliest, simplest, and least likely to
survive are hinged shutters that were attached to interior window casings and opened, like a
small pair of doors, against the walls on each side of the window. Because these shutters fold
into the room, disrupting any piece of furniture that is placed in front of the window, and because
they occupy wall space when open, they were often regarded as a nuisance in a later times and
simply removed. More common in the 1700s than later, such shutters were usually attached with
H-hinges, and close examination will often reveal evidence of the hinges on the side casings of a
window. Because folding shutters need to lie flat against the wall when open, their window
casings seldom had projecting mouldings. Thus, absence of mouldings, combined with a casing
design that provides for a rebate or recess around the window opening, are clues that a window
may originally have been fitted with folding shutters.
The second type of shutter, which often survives unknown to the modern homeowner, is the
sliding type. Fitted into thin pockets behind the wall plaster, sliding shutters can be slid out of
sight or pulled partly or entirely across the sashes. Sliding sashes are usually made in two units.
One covers the lower sash. A second, sliding on a grooved rail at the height of the meeting rails
of the sashes, covers the upper sash. Because the shutter rail was often regarded as a nuisance, it
was frequently sawn off and the shutters pushed into their pockets, covered with strips of wood,
The third type of shutter, and the most likely to survive in use, is the folding shutter set into a
deep window embrasure. Found only in more elaborate buildings, such shutters are hinged and
fold into two or more leaves. They require a thick wall that offers the depth necessary to house
the folded leaves of the shutter at each side of the window. In a framed building, this extra
thickness is achieved by double-studding the wall; in a brick building, the thickness of the
masonry usually provides most of the depth needed to house such shutters.
Very rarely, one will find window shutters of a different style, perhaps sliding on exposed rails
beside a window rather than in pockets within a wall cavity, or perhaps lifting upward from a
pocket below the window opening. A few grand houses of the early 1800s had double sets of
interior sliding shutters, one set solidly paneled, and the second set louvered like exterior
window blinds, admitting fresh air while excluding sunlight.
Window shutters of every period were fashioned in harmony with the style of joinery of that
period. Their design and details almost always match those of the original doors or other
paneling in a given room. Their architectural style will be in harmony with the style of the
window muntins unless the original sashes have been replaced.
Exterior window blinds, seldom seen until the end of the eighteenth century, became
commonplace during the early nineteenth. In New England, almost all exterior blinds except
those on stores or warehouses were of the louvered or “Venetian” pattern. Commercial building
might have solid, heavy exterior shutters clad with sheets of iron to seal the building against theft
Because of their fragile nature and exposure to the weather, original window blinds survive in
lesser quantities than original window sashes, especially those from the first half of the
nineteenth century. In general, the earliest window blinds have heavy stiles and rails. These
frames hold thick, fixed louvers whose ends are fitted into slots in the stiles of the blind and are
held in place by wooden beads applied over the slots.
Later blinds have thinner louvers, often with rounded rather than sharply beveled edges. By the
1850s, blinds were often made with louvers that are pivoted on dowels attached to their ends.
Called “rolling slats,” these pivoting louvers are stapled to wooden rods that link them together
and allow the angle of the louvers to be adjusted to improve ventilation when the blinds are
COMMON PROBLEMS OF OLD SASHES
An unmaintained window sash that has been exposed to the weather commonly loses putty on its
outside faces. Once the putty has fallen away, the wooden fillet that holds the glass may erode.
Panes of glass may loosen or crack from many kinds of impacts. On the interior face, the wood
of the sash may soften from condensation running down the windowpanes. Air may infiltrate
around the sashes or between the meeting rails. The mortise-and-tenon joints at the corners of
the sash may loosen, and the bottom rail of the lower sash may rot from chronic dampness at the
windowsill. The sash cords (or the more recent sash chains or steel tapes) may break from
fatigue. Sash weights may become jammed in the pockets, and spring balances on newer sashes
may loose their tension. Wooden parting beads or sash stops may wear from the friction of the
sash. The single glazing of the window may conduct heat and cold. For households with young
children, lead paint on the sashes or window frames may be a concern.
SOLUTIONS TO SASH PROBLEMS
If this litany of problems seems daunting, it should be remembered that the sliding wooden sash
is one of the most successful and enduring of architectural features. Sashes of the type that we
may expect to find in any old building have been standard building components for three
hundred years. Many sashes in use today have provided good service for some two hundred
years or more. The behavior of wooden window sashes is absolutely predictable. The
maintenance of such sashes has long been part of the repertoire of the building trades and the
Conversely, no type of replacement window has been on the market long enough to have proven
itself as a worthy successor to the wooden sash. No type of replacement window is as
appropriate for an old building as the sashes that were originally made for that building.
The simple secrets of keeping old sashes in use are repair if needed, maintenance, and protection.
Repair of sashes is not complicated; every part of an old window was made to be repaired when
necessary. A number of the articles cited in the following bibliography offer general hints and
fine points on sash repair.
Maintenance of sashes, though often neglected like any other household duty, is usually a simple
matter of re-glazing and painting, perhaps with the occasional replacement of a set of sash cords.
Maintenance goes a long way toward protection as well, but the best and simplest protection for
old sashes is installation of an outside storm window.
Storm sashes have been in use since the eighteenth century, and have been common since the
late nineteenth century. A storm sash or storm window is a temporary or permanent unit that is
affixed to the outside casing of a window, sealing and protecting the inner sashes against heat
loss and weather damage. With the addition of storm sashes, old windows often become more
energy-efficient than modern double-glazed replacement units, especially if the original inner
windows are weatherstripped or otherwise sealed against air leakage.
The most energy-efficient type of storm window has always been the traditional wooden storm
sash. Regrettably, such units have fallen into disfavor because of their weight and awkwardness,
the need to hang, remove and store them seasonally, and the ease with which their glass is
broken in handling. But for those houses that have them and those homeowners who are willing
to use them, wooden storm sashes remain an excellent defense against heat loss and an excellent
protection for historic inner sashes.
The most universal type of exterior storm window today is the aluminum unit. Aluminum storm
windows may be one of the older types with interchangeable storm glazing and screens, or the
now-standard triple-track storm window with self-storing storm glazing and screens. Either type
greatly increases the energy efficiency of single-glazed wooden inner sashes and protects the
wooden units against the effects of weather.
Aluminum storm windows have the added benefit of protecting the wooden inner sashes against
condensation. Because their glass is colder than that of the wooden windows, aluminum storm
windows collect and condense moisture that circumvents the inner sashes. Because their metal
frames cannot be harmed by moisture, aluminum storm windows safely handle condensation as
long as wooden window sills are kept painted and the weep holes at the bottoms of the aluminum
frames are kept open to drain properly.
Some people object to the fact that the flat, featureless expanse of glass in storm windows
obstructs a view of the hand-made glass and muntin divisions of older sashes. While it is true
that exterior storm windows obscure the character of historic wooden sashes, the protection
offered by outside storm windows may be regarded as an adequate compensation for a bland
exterior appearance. Others object to the projecting frames of aluminum units, especially when
the bare metal is exposed. Painting the aluminum frame the same color as the window casings
can soften the harshness of the metal. Those who want less visible exterior storm window may
want to consider storm units that fit within wooden exterior window casings.
Today’s marketplace also offers a number of interior double-glazing units. Often glazed with a
plastic rather than with glass, these units attach to the interior window casings or fit within the
inside window opening.
Inside double glazing is often employed where the exterior appearance of a building is
paramount. It is important to recognize that inside double glazing reduces heat loss, but does
nothing to protect historic wooden sashes. In considering such units, it is important to decide
whether it is desirable to be able to open windows for ventilation. It is also important to consider
whether inside humidity levels are likely to cause condensation on the historic sashes (which,
being on the outside, will be cold), and whether exposure to weather and sunlight is likely to
damage the historic sashes.
Wooden sashes are a three-hundred-year-old technology. They are an important and characterdefining
feature of any old building. Any building that retains its original sashes and glazing
thereby gains in integrity and significance.
Wooden sashes are also a simple technology. They can be protected against deterioration and
made more energy-efficient by equally simple technologies. The best method of preserving
historic windows and improving their performance is usually the simplest method, and often the
least costly one.
Bock, Gordon, “New Century Sash: The Fashions and Features Behind Post-Victorian
Windows,” Old-House Journal 25 (January-February 1997): 36-39.
Boorstein, James, “Wood Windows: Still Vital,” Traditional Building 7 (September-October
Byrne, Richard O., “Conservation of Historic Window Glass,” APT (Bulletin of the Association
for Preservation Technology) 13 (1981): 3-10.
Closs, Christopher W., “Repairing and Upgrading Multi-Light Wooden Mill Windows,”
Preservation Tech Notes, Windows Number 16. Washington, D.C.: National Park Service
Preservation Assistance Division, 1986.
Cullinane, John J., A.I.A., “Window Conservation: Rehabilitation vs. Replacement,”
Conversations with an Architect 1 (Spring 1994). PresINFOGroup, Suite 200, 1133 Twentieth
Street, NW, Washington, D.C., 20036.
Elliott, Cecil D., Chapter 5, “Glass,” in Technics and Architecture. Cambridge, Mass.: MIT
Feist, William C., “Replacement Wooden Frames and Sash: Protecting Woodwork Against
Decay,” Preservation Tech Notes: Windows Number 4. Washington, D.C.: National Park
Service Preservation Assistance Division, 1984.
Fisher, Charles E., III, “Installing Insulating Glass in Existing Wooden Sash Incorporating the
Historic Glass,” Preservation Tech Notes, Windows Number 11. Washington, D.C.: National
Park Service Preservation Assistance Division, 1985.
-----. “Interior Storm Windows: Magnetic Seal,” Preservation Tech Notes, Windows Number 9.
Washington, D.C.: National Park Service Preservation Assistance Division, 1984.
-----. “Rehabilitating Windows in Historic Buildings: An Overview,” in Charles E. Fisher, III,
ed., The Window Workbook: Successful Strategies for Rehabilitating Windows in Historic
Buildings. Washington, D.C.: U.S. Department of the Interior, National Park Service
Preservation Assistance Division and The Center for Architectural Conservation, College of
Architecture, Georgia Institute of Technology, 1986.
Garbe, Sharon, “Window Repair & Refurbishment,” Traditional Building 7 (September-October
Gilmore, Andrea, “Guidelines for Repairing Historic Windows,” Traditional Building 9
(January-February 1996): 77, 79.
James, Brad, Andrew Shapiro, Steve Flanders, and David Hemenway. Testing the Energy
Performance of Wood Windows in Cold Climates. Montpelier, Vermont: Vermont Division for
Historic Preservation, 1996.
Labine, Clem, “Revival of the Wood Window,” Traditional Building 2 (September-October
-----. “Seeing Clearly Into Historic Windows,” Traditional Building 4 (September-October
-----. “Storm Windows: Avoiding the Moisture Trap,” Traditional Building 4 (September-
October 1991): 26.
Lee, John Greenwalt. Window Conservation and Repair Specifications. Window Rehabilitation
Guide for Historic Buildings, pp. V-11—V-23.
Leeke, John C., “A Window on Sash: How to Make and Install Replacement Parts,” Old-House
Journal 23 (May-June 1995): 46-51.
-----. Wood Window Sills. Window Rehabilitation Guide for Historic Buildings, pp. V-3—V-10.
Lepre, Vincent, “Window Sash Manufacture,” Building Renovation (September-October 1993):
Meany, Terence. Working Windows: Repair and Restoration of Wood Windows. Bothell,
Washington: MeanyPress, 1997.
Monro, William L. Window Glass in the Making: An Art, A Craft, A Business. Pittsburgh:
American Window Glass Company, 1926
Myers, John H., Preservation Briefs 9: The Repair of Historic Wooden Windows. Washington,
D.C.: U.S. Department of the Interior, National Park Service Technical Preservation Services,
National Park Service. Window Directory for Historic Buildings. Washington, D.C.: U.S.
Department of the Interior, National Park Service Cultural Resources Preservation Assistance,
New York Landmarks Conservancy, Repairing Old and Historic Windows. Washington, D.C.:
Preservation Press, 1992.
O’Connor, Richard, “Perfecting the ‘Iron Lung’: Making the New Window Glass Technology
Work,” IA (Journal of the Society for Industrial Archaeology) 23 (1997): 7-24.
O’Donnell, Bill, “Troubleshooting Old Windows,” Old-House Journal 14 (January/February
Pacey, Antony, “A History of Window Glass Manufacture in Canada,” APT (Bulletin of the
Association for Preservation Technology) 13 (1981): 33-47.
Park, Sharon C., “Thermal Retrofit of Historic Wooden Sash Using Interior Piggyback Storm
Panels,” Preservation Tech Notes, Windows Number 8. Washington, D.C.: National Park
Service Preservation Assistance Division, 1984.
----- and Douglas C. Hicks, Preservation Briefs 37: Appropriate Methods for Reducing Lead-
Paint Hazards in Historic Housing. Washington, D.C.: U.S. Department of the Interior, National
Park Service Preservation Assistance Division, 1995.
“Re: Window Glass” (technical note), APT (Bulletin of the Association for Preservation
Technology) 3 (1971): 11.
Smith, Baird M., Preservation Briefs 3: Conserving Energy in Historic Buildings. Washington,
D.C.: U.S. Department of the Interior, National Park Service Technical Preservation Services,
Stumes, Paul, “Reinforcing Deteriorated Wooden Windows,” Preservation Tech Notes, Windows
Number 14. Washington, D.C.: U.S. Department of the Interior, National Park Service
Preservation Assistance Division, 1986.
Swiatosz, Susan, “A Technical History of Late Nineteenth Century Windows in the United
States,” APT (Bulletin of the Association for Preservation Technology) 17 (1985): 31-37.
Taylor, Thomas H., Jr., “Architectural Glass Repair: A Case Study,” APT (Bulletin of the
Association for Preservation Technology) 13 (1981): 31.
Townsend, Andrew, and Martyn Clarke, The Repair of Wood Windows, Society for the
Protection of Ancient Buildings Technical Pamphlet 13. London: Society for the Protection of
Ancient Buildings, n.d.
Weaver, Martin E., “A Short Note on an Early Sash Window Found at East Hampton, Long
Island,” APT (Bulletin of the Association for Preservation Technology) 10 (1978): 55-62.
Welsh, Frank S., “Eighteenth-Century Black Window Glazing in Philadelphia,” APT (Bulletin of
the Association for Preservation Technology) 12 (1980): 122-123.
Weeks, Kay D. and David W. Look, A.I.A., Preservation Briefs 10: Exterior Paint Problems on
Historic Woodwork. Washington, D.C.: U.S. Department of the Interior, National Park Service
Technical Preservation Services, 1982.
Wilson, H. Weber, “Window Glass,” Old-House Journal 5 (April 1978): 37, 42-45.
Wilson, Kenneth M., “Window Glass in America,” Building Early America. Radnor, Pa.:
Chilton Book Company for the Carpenters’ Company of the City and County of Philadelphia,