Whether you’re replacing existing timber sliding sash windows or restoring your contemporary windows to their former period elegance, take the time to select your preferred design and specification.

Interestingly, while box sash windows were created over 300 years ago, the design and style went on to evolve throughout the Victorian, Edwardian and Georgian periods. In 1850, for example, sash horns were added to reinforce the frames. Some windows have decorative sash horns pointing downwards on each end of the outside ‘central meeting rail’, while others also have them on the inside of the meeting rail pointing upwards.
Today, sash horns are no longer technically required, but remain a popular decorative design preference by many.


Another example of the design evolution are astragal bars, which developed from a simple square design to become rounded, and then evolved again to become an elegant fine lambs tongue shape and other popular profile styles. Astragal bars split the glass up into smaller panes (see below).


Similarly, even the depth of the meeting rail and bottom rail varies from era to era and area to area.


Most of our clients prefer to restore or replace the original design, integrating modern joinery techniques and glass technology to ensure strong performance. Laminated timber and high-performance glass, for example, ensure that you avoid the usual problems associated with timber sliding sash windows such as warping, rotting, condensation, rattles, draughts, external noise penetration and frequent repainting.


Regardless of where you’re based, be it in Surrey or London, we’ll help you make the right decision when it comes to selecting the right timber sliding sash windows for you.



Below, we’ve outlined the high specification that we insist upon from our approved manufacturers. You can also read about the upgrade options, should you wish to further extend the performance of your new period
sash windows.
Another example of the design evolution are astragal bars, which developed from a simple square design to become rounded, and then evolved again to become an elegant fine lambs tongue shape and other popular profile styles.

In the past, simple sawn timber – predominantly Nordic pine – was used for sliding sash windows. Nordic pine is a hardy slow-grown redwood that is known for its stability and ability to hold paint. Despite being longer lasting, hardwoods are less often used for sliding sash windows as they tend to twist and warp – a little more than redwoods.


Hardwoods also bleed resins into the paint, which isn’t an issue if you plan on varnishing your sliding sash windows, but can be troublesome for paintwork.
The pine or redwood windows that were fitted half a century ago, for example, are only just being replaced now.


The most popular and cost-effective timber for frames is cross grain laminated redwood, with laminated hardwood as standard for sills. Hardwood sills prevent that part of the window which sits on the damp exposed stone or brickwork from rotting. Cross grain laminated redwood is created by sawing the redwood into strips, and then bonding it back together with the grains facing in opposite directions. When the strips try to twist in opposite directions, they simply counter each other, and the frame doesn’t twist.


This dynamic stability is perfect for both sliding sash windows and casement windows. The life span of redwood sliding sash windows – assuming they are painted periodically – is about 50 years, which can be extended with refurbishment. South-facing windows generally need to be painted more regularly than north-facing windows because, contrary to popular belief, UV light is the main cause of frame rot – not rain! If you’d prefer a longer service life than 50 years, see the upgrade options below.

In the past, simple sawn timber – predominantly Nordic pine – was used for sliding sash windows. Nordic pine is a hardy slow-grown redwood that is known for its stability and ability to hold paint.

Teknos, a world-leading timber paint manufacturer (and our preferred paint), has conducted extensive research on the life span of timber windows.


This research has proven that where timber windows are sealed, painted and glazed in a factory (known as factory-finished), they will last up to 30% longer and require significantly less painting, repair and maintenance than windows that are glazed or painted on site.

Teknos, a world-leading timber paint manufacturer (and our preferred), has conducted extensive research on the life span of timber windows.

Choose from either a first fix or fully-finished installation with our approved window installers. First fix gives you the flexibility of having your windows installed into the opening, ready for your own builder to seal them in and complete the finishing touches to the interior.


Opt for the fully-finished installation, however, and our approved installers will do it all for you, including making good the internal plasterwork, installing and undercoating the internal window boards and period architraves.


Extend your painting cycles by applying 3-4 coats of Teknos timber microporous paint at the start or by having thicker coats applied. We’ve found that, compared to standard painting cycles of 2-4 years, this additional step can extend your painting cycles to 8–12 years. This technologically-advanced microporous paint allows the timber to breathe and prevents any flaking that you might see with oil-based paints. It essentially acts as a sun screen, preventing the sun’s harmful UV rays from damaging the timber underneath the paintwork. It’s worth noting that south-facing paintwork will require more frequent repainting than their north-facing counterparts.


There are a few ways you can protect the paintwork at home as well. Washing the polluted dust from the external faces with a sponge and water twice a year can have a big impact. Teknos sell cleaning and preservative liquids that you can add to your water when sponging down your windows. And when it comes to repainting, ensure you use the same water-based microporous paint as a base coat, which can be applied without sanding or removing the sashes, as you’d ordinarily do with oil-based paints. Once repainted, your windows will look brand new again.


We specify top-quality materials for your new sash windows as standard. These include:

  • Pre-stretched and plaited long-life and easy-clean nylon cords or heavy duty long-life spiral balances
  • Bearing-operated pulley wheels for long life and silent sliding
  • High-performance, long-life, double-glazed sealed units
  • Upgraded draught proof seals for warmth and sound proofing
  • Anti-twist engineered timber



If you have a flexible budget, and would like to explore upgrades, you can also choose:

  • Sash limit stops (for safety and security)
  • Accoya or laminated hardwood windows, that will extend the expected service life from 50 years+ to 80 years+
  • Safe & sound 6.8mm laminated glass for upgraded soundproofing and extra security
  • Secure By Design* specification for vulnerable areas of your home



*Secure By Design is a certified police initiative where enhanced security features are built into windows and doors to help prevent entry by would-be intruders.
We specify top-quality materials for your new sash windows as standard.
Period and contemporary timber sliding sash windows are available in a variety of design options. For more info, we’d be happy to email you details and accompanying photos – just contact us and ask!


For ease of opening the sometimes-heavy sliding sashes, each sash is balanced with either traditional weights and cords, or modern springs. Both work equally as well. Generally, modern properties have springs, as windows will usually be fitted onto the outer leaf of the brickwork so that the external visible frame can be made slimmer. Period property windows, on the other hand, are generally hidden behind the inner leaf of brickwork and show a little bit of frame from the outside. Heavier box sash frames with weights and cords are typically used here, however springs can be installed instead. Springs may require more maintenance over time but can cost less with some manufacturers. The only visible difference will be the absence of sash cords and
pulley wheels.



External and internal decorative sash horns were introduced onto sliding windows in the 1850’s to strengthen them, and to prevent the sash from sliding too far up or down which would damage the weights. Modern engineered windows don’t need this feature, however around 80% of homeowners opt for external sash horns, with around 20% choosing internal and external sash horns, simply as a period decorative feature. External sash horns point downwards on each end of the outside central ‘meeting rail’ for the top sliding sash, while internal horns point upwards and are located on either edge of the central ‘meeting rail’ for the bottom sliding sash.



Sash limit stops — also known as travel restrictors — are an optional security feature that prevent the windows from opening more than a couple of inches. This allows you to open the sash slightly for ventilation while preventing intruders from breaking in, and little ones from climbing out! There are two styles to choose from: a key-operated barrel stop or an angel restrictor.


Angel restrictors are permanently fitted to either side of the sash; you just push them in to enable the window to be opened. The restrictor will then automatically pop out and secure the window, once closed. Barrel stops, on the other hand, require you to physically remove the restrictors with an Allen key in order to open the window and replace them to lock it. Angel restrictors are the most popular choice among our customers as they don’t require a key and lock automatically when you shut the sash, however barrel restrictors are common too, particularly if they already exist on old windows or are the preferred period visual look.



External pull handles — also known as D handles — are an optional extra that can be fitted onto the outside bottom edge of the upper sash. This means that the upper sash can be pulled down from the inside or outside. That said, this can also be achieved by grabbing the meeting rail, so they are not a necessity and more of a period design feature. Around 25% of our customers choose this option. Colour options include brass, gold, chrome, brushed silver (satin), black and white.



Fasteners are the window locks that sit on top of the meeting rail to ‘fasten’ the two sashes together. There are different types depending on your preference. The three most popular options include modern and period Fitch and Brighton fasteners. The most popular (around 80%) is the semi-circular heritage or alliance type which is available with or without key locking.



There are two types of lift handles: curled or eye (also known as a pole eye). About 95% customers opt for the curled option. An eye lift handle can be fitted to the inside top of the upper sash on very large windows, so that a pole with a hook can be used to pull down the upper sash. When an eye is fitted to the upper sash, rather than the lower sash, it is known as a pole eye.



Single or double-glazed panes are held into position with beading. In the past, putty beading was applied to the outside, like plasticine, and allowed to dry before being painted. The three types of beading available include:


  • Internal timber beading (65% popular)
  • External timber beading (30% popular)
  • External putty beading (5% popular)


There is also a variety of period timber bead shapes available.


Internal ‘putty-shaped’ timber beading is a popular option as it affords you better security: the glass can only be removed from inside your home and not from the outside by prising the beading off. Additionally, external timber or putty beading can suffer from water and/or UV light damage over time and therefore requires more servicing.


External putty beading is the traditional beading method and is sometimes specified by timber purists or in conservation areas. External putty beading is more expensive as it should ideally be applied in factory conditions (not on site) and takes approximately three extra weeks to apply and dry at a controlled rate to avoid going brittle or cracking.



White frames are the most popular colour for sliding sash windows, however you are welcome to choose from any of the RAL, Dulux or Farrow & Ball colour ranges as well. Dual colour options are available, with differing external and internal coloured frames; alternatively you can select one colour for the outer frame and another for the sashes.



In the olden days, thin panes of glass could only be made in small sizes — otherwise they’d snap. So, a large pane of glass was made by joining together smaller pieces using lead or timber bars, known as astragal bars. Nowadays, this design is still popular and over 25% of customers choose this period design feature. There are many patterns to choose from, including squares, centre bar or border design. The astragal bar shape (profile) itself can be chosen from a selection, and will depend on the period look
you require.



A ‘no-salesperson’, no-obligation emailed quote

A free home visit, if required (for those in London and Surrey)

CAD drawings with detailed specifications for each quoted product

Realistic before & after photo simulations, if required

Timber Sliding Sash Windows Image 1
Timber Sliding Sash Windows Image 2
Timber Sliding Sash Windows Image 3
Design your dream conservatory with our interactive visualiser and preview it in Augmented Reality.

Conservatories and orangeries have long been a popular extension style, as they can be designed specifically to complement the design of your property. What’s more, modern performance glazing and next-generation thermal conservatory roofs, pillars and posts allow for optimum temperature control throughout the seasons.

Say goodbye to overheating in the summer, and ice-cold temperatures in
the winter!
Online photo quote service with design advice plus scale drawings
Online photo quote service with design advice plus scale drawings

Before arranging a home visit you can now get an accurate quotation and scale drawings by simply sending us photographs and any rough measurements you may have. If you know your main needs with regards to the products and design of your project - great - if not, we can help and advise where necessary.


Use the submission box to make contact, or email or call with any questions. We can arrange a free home visit to take measurements and go through your options at any stage. We look forward to hearing from you.


Preferred quotation method - tick option

Email quote
Call me back
Home visit
Ask a question
I will upload some images for a photo quote

Please note that the images you send must not exceed 10mb in total, if the images are larger please email us directly or try zipping them. If you are experiencing difficulties then please contact us on 020 3011 1444 and we will be more than happy to assist you.

© Copyright 2022 London Timber Windows and Doors Ltd All Rights Reserved. Company number 10273992