Advice about Wooden Windows Everything About Wooden Sash Windows
Go green with our environmentally friendly timber windows and wooden doors.

Everything About Wooden Sash Windows

Table of Contents

Introduction to sash windows

Do you wish to see the classic charms of wooden sash windows embracing your living space at your newly renovated home? Have you thought of restoring your wooden sash windows as a project to rejuvenate your home? However, I suppose the charm of timber sash windows has fascinated you to learn more about them. In that case, we will tell you all that you should know about timber sash windows.

But hold on, you might be wondering, “Which wooden sash windows are the best for my home?” Well, you’re in luck. Our service is here to assist you in making an informed choice about your wooden sash windows.

We know it is challenging when it comes to making decisions. That’s why we have something more to offer than information. We’re ready to connect you with our experienced, professional and Authorised Installers, who are FENSA Registered, right in your area within the UK. Imagine the convenience of having experts at your doorstep in just a matter of hours, ready to bring your vision to life. You can search for a recommended installer near you or contact us for help.

When you get a quote from us, and you’ll be pleasantly surprised to know that all our quotes come completely free and without obligation.

What are wooden sash windows?

Sash windows or wooden sashes have become the epitome of grace, class, and elegance in house designs. The windows are designed with an exceptional kind of uniqueness to stand distinctively amidst other ordinary windows of time for generations. Your house can receive an added charm of nature through a wooden sash window that is traditionally made of wood. These include sashes, which are two panels that slide vertically in the window frame.

They stand out because of a mechanism that enables easy opening and closing. The sashes within the frame, can sometimes feature a gridded Georgian bar pattern, which divides the glass into small windowpanes to give each pane its classic and almost fairy-tale appearance.

Which type of sash window is best for me?

Wooden sash windows are more than just a feature in your home; they are a glimpse into history, a portal to the past, and a testament to craftsmanship. These windows come in various types, each with its own unique charm and functionality. Let’s see each of the wooden sash windows.


Wooden box sash windows

Wooden box sash windows are the symbol of tradition, and have adorned homes for ages. Box sash windows are the original type of sash windows that still reside and are replicated in many buildings today. Their flawless glide is made possible by a symphony of counterweights hidden within the frames sides. The elegant opening is orchestrated by a chain or braided nylon sash chord that is leveraged by pulley wheels.

These windows, which are made of hardwood or softwood, offer a blank slate for your imagination. Using whatever colour speaks to your nature, paint them. When the frame is mounted, usually behind the external brick work, you’ll see it is subtly hidden from the outside, leaving only a faint trace of wood externally.

Buildings were made to accomodate Box Sash windows, as the brick work on the inside is usually about 160mm wider then the outside brickwork. The “boxes” are the sides of the window frame which are constructed like a box to accomodate and hide the counter weights inside them.

In the UK, the phrases “sash windows” and “box sash windows” are sometimes used simultaneously. However, historically, the latter has more literal and symbolic significance. Even while contemporary or more modern sash windows are lighter, they both capture the marvel’s ageless beauty.


Spring sash windows

Spring sash windows are the solution if you want a modern take on classic sash windows. Instead of using the traditional sash weight and rope arrangement, they used a covert spring device, which makes a more compact opening system. This innovation makes the appearance more streamlined, and installation is possible in more modern buildings where the brick work is the same on both the inside and the outside.

Spring sash windows have a slimmer frame, as there is no need for the box sections, as there are no weights to accomodate.


Tilting sash windows

The tilt & slide sash window is a game-changer for those who want an easy clean option for windows located on higher levels. These stunning windows have an extra tilting benefit in addition to functioning like the conventional sliding sash windows.

They move gently when in use, but they may also tilt approx 50 degrees inward. This clever design provides a practical way to clean the outside panes from the inside for high windows in busy cities. These windows perfectly capture the union of form and function, fusing the beauty of a sash window with the usefulness of simple cleaning.


Fire escape sash windows (Sashment windows)

Never compromise safety for fashion. Fire escape sash windows are designed with your safety in mind while blending in perfectly with a room’s aesthetics. These windows offer a speedy escape path in the case of a fire since they open entirely, much like doors. They resemble conventional Box Sash windows in appearance nearly precisely. Still, they hide a secret: an emergency release mechanism that allows quick departure from the inside.

These windows provide a lifeline in instances when space is at a premium, enabling you to comply with fire standards while preserving the appeal of timber sash windows. Wooden sash windows are not a one-size-fits-all affair. They come in various styles, each with its unique charm and historical significance. Let’s look at these classic window designs and discover the options available to add character and personality to your home.

Astragal Georgian bars or real Georgian bars?

A double set of sliding sash windows, showcasing the versatility of designs by authentic timber windows ltd.
An example with Astragal glazing bars. 95% of all windows with glazing bars on our site are Astragal.

Firstly I should explain the difference between an Astragal Georgian bar and a real Georgian bar.

Real Georgian bars are made to accomodate separate pieces of glass between each bar. So one opener could have between 2 and 8 pieces of glass, depending on the style you want and how many squares/sections you want in each opener. Real Georgian bars can only accomodate single glazing or extra slim double glazing which can be between 12mm and 16mm in thickness – 4mm outside / 4 to 8mm cavity space usually filled with Krypton or Argon gas for insulation benefits / 4mm inner pane.

Due to the huge push for improved energy efficiency, yet maintaining the sash windows traditional appeal, Astragal Georgian bars became the norm. Most glass is now double glazed and is usually and optimally 24mm thick – with a 4mm pane inside and outside with a 16mm space cavity in the centre which is usually filled with Argon gas for maximum insulation and cost effectiveness. To date, it is impossible to manufacture 24mm glass without having bulky edges (the spacer bar and butyl that seals in the Argon gas), so it became the norm to make the Georgian bars to sit ontop of the glass and to insert a spacer bar inside the double glazing to make it look like the glass units are still separate units, but they are not. If you have bulky edges which are about 15mm each side, then once put next to each other you already have 30mm, plus you need the wood going all the way through to house the glass, which would make for very unsightly bars at around 45mm in width. If the originals were around 18 to 22mm then 45mm isn’t really an option.

So when you see a window with Georgian bars on it these days, the chances are that it has Astragal Georgian bars, not real ones. Astragal bars are the easiest and most cost effective solution to maintaining the traditional appearance of real Georgian bars.

Glazing options for sash windows

Glazing options for wooden sashed windows.

Glazing options for sash windows are much the same as any other window or door, with some exceptions.

Because sash windows rely on a counter balance system to allow operation of the openers (sashes) the weight of the glass is something that must be considered. Most sash windows can accomodate 24mm glass if it consists of 2 x 4mm panes and if the window is tall enough, it should be able to accomodate Laminated glass which is 6.4mm thick instead of the standard 4mm.

The height of the window is only significant because the higher the window the more room there is for larger weights or larger springs to equalise the weight of the openers.

Sash windows that are short and wide often will not be able to open all the way, because there is not enough room for enough weight to counter balance the openers.

The choice of glass for your wooden sash windows is pivotal in determining your living space’s ambience, energy efficiency, and character. Here are some glass options to consider:

  • Single Pane Glass: Most old-fashioned sash windows are made of single-pane glass. It is an old technology but hardly provides the desired warmth with minimal energy efficiency compared to new double glazing products.
  • Double Glazing: Double glazing has two glass panes which are filled with either Argon gas or Krypton gas between them. One major enhancement to Double Glazing that was made in the last decade was the introduction of Warm Edge spacer bars, which offer a significant improvement as the plastic prevents conductivity of the heat and the cold. Modern double glazing used now, offers good insulation, and minimises heat loss. It is perfect for keeping your house warm while saving you money on electricity bills.
  • Triple Glazing: As triple glazing needs to be about 40mm thick overall, it is not used on Sash windows as it is too bulky and too heavy. If manufacturers made frames that could accommodate triple glazing the result would not be very traditional or authentic, the frames would be very bulky and would not replicate the timeless beauty of the Sash Window.

Hardware options for sash windows

The hardware and furniture on your wooden sash windows are functional and serve as exquisite accents, adding character to your home. As with most products these days, there are hundreds of types and variations available on the market so no window company can offer them all. We are how ever, happy to install any type of hardware you wish, so long as it fits properly and functions as it should.

The common selection of colours are: black, white, polished chrome, satin chrome, polished brass, satin brass and pewter.

Here are some furniture options to ponder:

  • Sash Locks: Located on the mid rail, sash locks hold the windows closed. Sash Locks help keep your window shut tight and safe. Whether you want a more traditional design or something of a contemporary style, it all depends on how you want your home to look.
  • Sash Lifts: Usually located on the bottom of the bottom opener/sash. They are not only important in allowing easy opening of your windows; they add on as points for embellishments or customisations. They are available in numerous designs with different dimensions and surface coats that fit almost any room design.
  • Sash pulls: Usually located on the bottom of the top opener/sash on the outside. They allow users to open the top opener by first opening the bottom opener and then pulling down the top one, through the botttom of the window.
  • Sash Pulleys and Weights: The pulleys are located on the side of the frame and the weights are hidden inside the boxes. If Springs are used then they are housed in either the openers or the solid frame. Sash windows can effortlessly slide as they have a hidden pulley and weight system within the window frame. While keeping the originality of the window, there are several materials and designs that you can select to see that everything works smoothly.
  • Child Locks / additional security fasteners: In addition to the Sash Locks, you can have these additional locks installed to allow your window to be open but also secured so it can not be opened more than 100mm, this way you can be assured no one can creep in and children can’t fall out! These are highly recommended by us!

Some other options are available from our Sash Window hardware supplier here.

The names of each part of a sash window

Decorative horn options

The decorative horns on sash windows are located on the external side of the window, at the bottom of the top sash/opener. Additionally and occasionally, these decorative horns can also be made for internal side of the window and can be part of the bottom sash/opener as well.

Be careful not to mix up the term “horns”; as many people also refer to horns as part of the windows cill, specifically horns can also be the part of the protruding window cill that wraps around the brick work, usually for 50mm, on the outside.

Types of wood used for sash windows

Types of wood used for sash windows.

Selecting the right type of wood for your windows is a crucial decision that can impact not only the aesthetics of your home but also its longevity and performance. Two primary categories of wood for windows are hardwood and softwood.

Hardwood options

Oak: Oak is often considered the gold standard for hardwood window frames, though it has its draw backs. Its remarkable durability, beauty and resistance to decay make it a top choice. Oak exudes a timeless and rich beauty that adds character to any home. 

The draw backs with Oak are that it can fade quickly as a result of UV rays. Also it contains a natural tanin which can stain the paint on the outside. Professional window manufacturers avoid these issues by using end grain sealer and high end paints which are proven to be effective in protecting and preserving the Oak properly.

If you choose Oak because you want to see the Oak internally, we would recommend having the internal side stained and the outside to be painted in a solid RAL colour or white, to avoid UV issues and degradation of the external elements.

Mahogany: Mahogany comes in all sorts of types, but the 2 most commonly used types for external joinery in the UK are Meranti and Sapele. These are hardwoods renowned for its exquisite beauty and strength. It features a fine grain and a rich reddish-brown hue that deepens with time. Mahogany is naturally resistant to both rot and insects, making it a solid choice for sash windows and all external joinery.

The allure of Mahogany lies in its timeless elegance, enhanced by the knowledge that it can withstand the test of time, both in terms of durability and aesthetics.

Softwood options

European Redwood: Redwood is a member of the Pine family, also known by various names like Red Deal, Yellow Deal, Softwood, and more, has been a stalwart in European window construction since the late seventeenth century. This is the most common type of softwood used for external joinery through out the UK as it is very durable, resistant to decay and is also very economical and easy to work with. As with all types of timber, when treated and painted with high quality wood protection, Redwood should last for many decades with minimal maintenance.

It encompasses several pine, fir, and spruce varieties imported from Northern Europe. The European Redwood available today is primarily sourced from sustainable plantations.

The choice of Redwood pays homage to tradition and is a testament to its enduring popularity over the centuries. Its charm lies in its authenticity and connection to a bygone era.

Accoya: Accoya wood represents a modern revolution in window frame materials. It is engineered timber, grown from sustainable sources, and backed by 80 years of extensive research. Treated with acetic acid that penetrates deep within the wood, Accoya is preserved and strengthened. It boasts a class one durability rating, the highest level of durability, making it the top choice for window frames.

Authentic Timber Windows Ltd has not offered Accoya in its product range for 2 reasons: 1. It is extremely expensive, and 2. We believe in natural products and not chemically induced products which may affect the recyclable capacity due to its chemical treatments and the unknown affect on the environment at its end of life.

Douglas Fir: Douglas Fir can be hard to source but is a premium-grade softwood that finds its home in many parts of the world.

Though it can be prone to splitting and is somewhat brittle, Douglas Fir remains a top-notch choice for sash windows. Its premium status is often reflected in its price. Still, the benefits in terms of insulation and safety can make it a worthwhile investment.

Types of paint or stain available

Water Based and Micro-porous paint: This type of paint is now the norm for exterior joinery. As with many products there are a lot of manufacturers in the market and only through trial and error can anyone really know which is the most adhesive and most durable. After physically testing various brands over years and years we decided stay with Renner, as it proved itself to be far superior over the competition. The Renner paints we use are exceptional at protecting the wood in all weather conditions.

The downside of all water based paints is that, when used properly, they take 24 hours to dry between each coat. So when we apply 4 coats of paint – 1 impregnation, 1 coat of primer and 2 topcoats, (and end grain sealers in between) it takes a full working week just to paint them and to allow the proper drying times between coats. There are no shortcuts when quality is your primary goal.

Other types of paint have been phased out over the years due to Health & Safety concerns with paints that contained Lead and other metals or chemicals which were found to be dangerous during application or years afterwards.

Construction methods of a sash window

Different manufacturers do things in different ways, and for all sorts of reasons, but usually because of cost effectiveness. So, to save time on their production line, many manufacturers will buy the ready made elements of timber, profile them through their Spindle moulding machines and simply glue the corners together and paint them.

We at ATW dont want to take any risk on behalf of other companies who could be taking every possible opportunity to cut manufacturing costs.

So, we do everything ourselves, from scratch. This way we control the wood we use, the moisture levels and the type of glues used to engineer it into elements that will not bend or distort.

Wood Preparation:

We buy planks of wood, cut them to the required dimensions, plane them several times so all sides are equal, then we leave them sitting in the factory for several weeks to acclimatise.

Cutting and profiling:

Once checked again and after any mistakes or bowed elements are removed, we continue to cutting it into the required dimensions for each window or door that is ordered. Once dimensions are correct, we profile it through our machines to get the required profiles correct and then we glue the elements to make them into frames or openers.


Products are then placed through a 2 sided flat surface sanding machine to ensure perfect flatness and smoothness, then they are manually checked for any mistakes and are manually sanded in places the machine can not access, ready for end grain sealing and then painting.

Applying wood protection:

All products go through our rigorous hand sanding process and are treated with end grain sealer and then painted 4 times, as above.

Applying weather proofing:

Once they are painted, we start inserting and fixing the weather proofing gaskets to prevent wind, rain and noise from escaping through the connected sections.

Glazing for maximum security:

Next the items are moved to the glazing area and glazed accordingly with our own unique Double Seal system with Butyl tape and additionally capped off with Low Modulous silicone to ensure they never ever leak.

The second reason we glaze like this is to ensure maximum security is achieved in our products as no one can easily remove our glass without spending hours and hours to remove one piece or by breaking it. Many glazing methods allow the glass to be easily removed, but this also results in windows or doors that are vulnerable and appealing to burglars.

Item assembly & Hardware installation:

Items are put together and tested for air leaks or any other faults that may have occured through production. If they are ok the hardware is installed as per the customers specifications and tested on all items.

Quality control:

Our quality control process involves the complete testing by opening and closing of all moving parts and mechanisms numerous times to ensure they operate as intended. Stickers are then placed on each item and each QC checkpoint is signed off by one of our qualified staff.


Our packaging process includes labeling each item in correlation with the item on the Order Confirmation so customers always know which item is which, so they know which room in the building it is supposed to be for.

Corners are protected with U shaped foam and items are wrapped in cling foil to hold all the packaging in its place during transit to our customers. We also tear holes in the cling foil to ensure the wood can still breath to avoid excessive moisture building up inside the foil.

The Pros and Cons of wooden sash windows

The good:

  • Wooden windows add value to properties and are a long term investment, especially in prestigious homes.
  • Wooden sash windows are and always will be the “original sash windows” that offer authenticity, warmth and beauty; just like the originals have done so for over 100 years.
  • Wooden windows are the only Environmentally Friendly option which consume far less resources to manufacture and recycle at the end of life.
  • Wood is a natural and managed resource, and it is abundant in nature. We ensure more trees are planted to replace those used for windows, doors and hundreds of other purposes.
  • Wooden sash windows are the only accepted type of window in true Heritage and Conservation buildings.
  • Wooden windows are timeless and will never look out of place.
  • Can be rejuvenated, the colour can be changed, or customised many times through out their life, unlike uPVC.
  • Can be customised to suit any building, style or architecture.

The not so good:

  • The price of well made wooden windows is considerably more than uPVC windows. They are an investment in your home.
  • A little maintenance – wooden windows should be inspected every few years to ensure the paint has not been perforated to ensure the bare wood is not exposed to weathering.

Q: How much do double glazed wooden sash windows cost?

A: The average cost of a “good quality” wooden sash window can range from £845 to £2000 or more, depending on factors like size, hardware, glass type and design.

The price of a wooden sash window can vary considerably depending on the quality of components used to manufacture it. Some manufacturers focus on using the “cheapest” components possible and inevitably can deliver a “cheaper” product. This “cheaper” product may only last a few years, depending on many variables.


Q: How long do timber sash windows last?

A: Quality focussed manufacturers, such as Authentic Timber Windows Ltd, simply will not entertain or use components that risk being inferior to the best available, resulting in a window that is amongst “the best available”. A well made window should at least last for 50 to 100 years or longer, with just a little maintenance and an occasional re-coat. Our product is made with experience, confidence and pride to ensure its durability and maximum ROI (Return On Investment).


Q: Why are wooden windows more expensive then uPVC or auluminium windows?

A: If you have read this article in full, you should now be starting to understand why they cost more. Manufacturing windows from wood involves so much more work and a lot more processes and a lot more investment into labour & machinery than anything else.

Working with wood and producing products from it is a very time consuming and specific process that requires a lot of skilled workers to produce the final product. It also requires a higher skilled installer to install wooden windows, if any damage is caused or the paint is scuffed during installation then the installer needs to know how to re-protect the wood properly to avoid moisture issues.

uPVC and aluminium windows are simply made from lentghs of plastic or aluminium, joined together and glazed. There is no sanding, no moisture control, less labour, less skills, no knots to control, no faults to control, no painting for uPVC etc etc etc.


Q: How do wooden sash windows work?

A: Wooden sash windows operate using a system of counterweights and pulleys, allowing for easy sliding and secure positioning. Spiral (spring) balances or traditional weights and cords are used to hold the weight of each sash in their desired position.


Q: I would like to ask more questions about your sash windows, where can I find out more information for my project?

A: Please go to our contact page and send us a message, we are always happy to help.

Search for answers
author avatar
Stephen Earle Director
A perfectionist, designer and manufacturer of world class timber windows & doors. Motivated by a desire to establish a company offering superior, high-security, and timeless handcrafted timber windows and doors, Stephen collaborated with like-minded artisans to found Authentic Timber Windows Ltd in 2006. The company's mission was to bridge traditional artisanry with modernity, creating wooden windows and doors that seamlessly blended traditional or modern aesthetics with high-security functionality. As the Founder and Director of Authentic Timber Windows Ltd, Stephen played a pivotal role in shaping the company's vision and strategic direction. His commitment to excellence and a customer-centric approach quickly positioned the company as a leader in the bespoke timber windows & doors market. Under Stephen's guidance, Authentic Timber Windows Ltd gained a reputation for delivering superior & durable windows & doors; whilst paying attention to detail, and providing exceptional customer service.
Scroll to Top