4

Making traditional and

modern windows

INTRODUCTION

Although uPVC (unplasticized polyvinyl chloride)
windows and exterior doors with double- glazed sealed
units have proliferated in the UK in recent decades,
it seems likely that this trend may change soon.
Research informs me that many window design-
ers, seeking to cut carbon emissions and improve
overall thermal performance are switching back to
timber as a renewable and sustainable material with
natural insulating properties – and are using low- E
(emissions) glass in the sealed units. This renewed
interest in timber windows has arisen from the
Government’s drive to reduce the carbon- footprint
of houses by 2016; and a need to meet the recently
amended Building Regulations Part L1A and L1B:
Conservation of fuel and power in new and existing
dwellings.
It will not be easy to overcome the tarnished image
that many people have of timber windows (usually
gained from expecting them to survive maintenance
periods far in excess of the required 3 to 4 years).
However, many manufacturers are now upgrading
their designs. This includes using laminated timber
sections for stability and extra strength and using
quality redwood (such as Douglas fir) for durability
and longevity. Timber is also treated with water-
based preservatives that usually contain biodegrad-
able fungicides and insecticides; and the completed
windows can be given high- performance base- and
top- coats of water- based paint or stain before leaving
the manufacturer. Note that water- based coatings are
now believed to give more protection than solvent-
based coatings for exterior woodwork. However, where
greater durability is required, a powder- coated alu-
minium cladding can be applied to the external face
of the windows – especially in places where periodic
repainting is impractical, i.e. medium- and high- rise
buildings.
Whether the legal demands of the amended
Building Regulations’ Approved Document Part
L1B will affect the work of the individual small-
works joiner/installer of replacement windows is not

yet known, but if not, my recent research conveyed

that there is still a fairly big demand for the replace-

ment (renewal) of like- for- like (upgraded) wooden

windows – especially so- called boxframe windows

with top- and bottom- hung sliding sashes. Wooden,

stormproof casement- windows, with improved air-

and water- tightness are also being used in newly- built

houses. The upgrading of windows will be covered at

the end of the chapter.

BOXFRAME WINDOWS AND

DOUBLE- HUNG SASHES

Boxframes in their original form were designed

to accommodate and conceal the cast- iron or lead

sash weights, which counterbalance each glazed sash

window. The balanced sashes (which allow and

retain a variety of open- or closed- positions) are

moved up or down in two side- channels separated

by parting beads. The sashes are linked to the sash

weights by means of sash- cord or (for large, heavy

sashes) sash- chain passing through two pairs of sash

pulley- wheels sunk into the upper area of the pulley

stiles. A removable pocket is cut into the base of

the pulley stile on each side, concealed behind the

side- edges of the bottom sash, to allow access to the

weights for initial hanging and renewal of broken

sash- cords. Note that another type of sliding- sash

window (covered later) uses spiral balances instead of

balanced sash weights.

Details of a boxframe and sashes

Figure 4.1(a): There are many component parts

to these windows and the elevational drawing at

Figure 4.1(a) indicates the various detailed sec-

tional views that should be studied and referenced

to the list of common parts and sizes given under that

heading.