Timber Sash Windows
Introduction
I attended the Wrexham Traditional Building skills Timber Sash Window Course. It has provided me with an understanding of timber windows Pre -1919 from their design; to how they function & repair; the window components, ironmongery and how the windows are installed in the building.
The Workshop
Hand Sketch- Sash Window Types
Hand Sketch Diagram - Sash Window Components
1. Top Rail: The top horizontal framing member of a sash.
2. Box Frame: Sometimes referred to as a ‘jamb’, the main box frame consists of three Timber Linings.
3. Sash Cord: The waxed type is best- it runs over the Pulley Wheel and holds the weights. Spiral Balancers are an alternative.
4. Weight Pocket: The weights hang in the pockets created by the timber linings on each side of the window.
5. Parting Bead: A long, narrow vertical seal that fits in the box frame to form separate channels for the upper and lower sashes to run in, and holds the top sash in place.
6.Staff Bead: A moulded piece of timber made up of four sections, pinned around the BOX FRAME, which aids airtightness when draught proofed and also holds the bottom sash in place.
7. Meeting Bars/Rails: The horizontal framing members which meet the two sashes together in the middle. Their adjoining faces are bevelled so they close together tightly.
8. Stile: Vertical side framing member of a sash — there is one each side.
9. Apron: A decorative panel or cladding beneath the window. Not on all sash boxes.
10. Box Cill: A horizontal bottom section of the frame fitted internally at the base of the sashes. Shaped so that water flows away to the outside.
11. Bottom Rail: The bottom horizontal framing member of a sash.
12. Weight: A pair of lead weights hung on the Sash Cord counterbalance each sliding sash. The sash and weights must weigh the same.
13. Wag Tail: A strip of timber inside the box frame that separates the weights. Also known as a ‘parting slip’.
14. Timber Linings: The sections that form the casings of the box frame – which must be hollow to house the Weights – are made in three parts: the ‘outer’, ‘inner’ and ‘pulley’ linings.
15. Pulley Wheel: A pulley mortised into the top of the pulley lining; the sash cord passes over it to counterbalance the weights.
16. Glazing Bar: A vertical or horizontal framing member that divides the panes within the stiles and rails. Each rebated – a cut which forms a groove – to hold the single-paned glazing or on replacement bars double glazing. Georgian sash windows have ‘six over six’ panes, but other configurations are common across London.
17. Soffit Lining: The windows head is made up of the main inner and outer TIMBER LININGS as well as a separate soffit lining; glued triangular blocks provide strength.
History
17th- Century
Development of Window Designs in the 17th Century, The size of glass panes that could be economically manufactured was increasing. The days when lots of 4 inch or smaller panes had to be pieced together with lead were in the past. At some point around this time putty was invented. New styles of architecture were coming in from the continent, Neoclassical and Baroque. This style change demanded a more vertical window proportion. The French seem to have come up with timber constructed windows with a bottom sash that slid up and was held in place with pegs.
Chatsworth House - 1687
18th- Century
Georgian timber sash is amongst the oldest original windows you’ll find still in use. They are the picture of elegance, and they immediately evoke the style of the period. They achieve this with their distinctive six-panel grid design on both top and bottom sashes - typically set back 4iches. That six-grid design didn’t come about by accident. Georgian architecture demanded large windows, but 18th-century glass technology limited the maximum size of the panes due to the glass being spun making it near impossible to create larger panes. The solution? Split the sashes into smaller areas with thinner astral bars that held smaller panes in place. They are charming, authentic and distinctive in design.
Buckingham Palace 1703
19th- Century
One of the first to incorporate what is now known as the run-through sash horn, Victorian Sash Windows tended to favor a ‘two over two-panel’ grid design on both the top and bottom panes - Sash windows found in Victorian England were much more lavish than those that came before, thanks in part to advances in glass technology. Because Victorian windows boasted larger, heavier glass panes to let in additional light, sash horns were added to remove some of this additional strain and strengthen sash joints.
Victoria Building, University of Liverpool - 1892
20th- Century
Twentieth-century and the dawn of the Edwardian era, sash windows reached their peak, in terms of their popularity and their elegance and style. The most fashionable sash window design was the ‘six panes over two panes’ configuration, reviving Georgian style and Victorian technology, to produce a final product with the same classic aesthetics but including much larger glass panes, thus letting in more light. However, Edwardian joiners faced the same problem as the Victorians. Large glass panels with fewer astral bars to support them added extra strain to sash joints. Like the Victorians, they overcame this with sash horns, which allowed them to build large, strong, rigid sashes. In turn, they created a simple, yet effective style of sliding sash window.
Port of Liverpool - 1907
Influences - Life Style - Manufacturing - Stylistic Approach
Fun Window History : Window Tax
This tax was first imposed in England in 1696. It was intended to be a progressive tax in that houses with a smaller number of windows, initially ten, were subject to a 2 shilling house tax but exempt from the window tax. There was a strong agitation in England in favour of the abolition of the tax during the winter of 1850–51, and it was accordingly repealed on 24 July 1851, and a tax on inhabited houses substituted.
As the bricked-up windows prevented some rooms from receiving any sunlight, the tax was referred to as daylight robbery.
The Modern Timber Sash Window
The Modern Sash Window is typically double glazed, manufactured in a factory painted but still traditional the same concept. In the U.K. today Sash Windows are still found in many listed buildings - as they are made of timber they have to be maintained/ replaced exactly as the original (which can be a costly exercise)
Manufacturing Timber Sash Windows- Traditionally made with hand tools and simple timber sections. Housing joints are used to create an outer box frame where sashes simply slide vertically within a channel created by the use of beads to separate.
Common Faults:
- Painted Shuts
- Leaking
- Snapped/ Frayed Sash Cords
- Rot
- Swollen Timber
- Broken Glass Panels
- Failed Joints
- Dry Mold - Only bad at certain types of conditions.
Reviving and Repairing Timber Sash Windows
1. Remove old windows from the window frame
2. Remove decaying timber in the units, frame or sill
3.Splice in new timber - Occasionally required, where existing timber is beyond repair
4. Fill all cavities - Epoxy resin VR90, moulded to match the existing profile
5. Replace cords & service pulleys - Correcting the sash balance to ensure smooth operation
6. Upgrade the seal - Sealing System (VPSS), which virtually eliminating draughts and rattles. At the same time, the Ventrolla Sash Removal System (SRS) can also be fitted to ease future painting, cleaning and maintenance.
Conservation and Restoration
Conservation and Restoration of immovable cultural property describes the process through which the material, historical, and design integrity of any immovable cultural property are prolonged through carefully planned interventions
Conservation
/kɒnsəˈveɪʃ(ə)n/ : To consider factors that deal with issues of prolonging the life and preserving the integrity of architectural character, such as form and style, and/or its constituent materials, such as stone, brick, glass, metal, and wood. In this sense, the term refers to the "professional use of a combination of science, art, craft, and technology as a preservation tool"[1] and is allied with – and often equated to – its parent fields, of historic environment conservation and art conservation.
Restoration
/rɛstəˈreɪʃ(ə)n/ : The action of returning something to a former owner, place, or condition.