What Is Accoya and Why Is It Used for Timber Windows and Doors?
If you've been researching bespoke timber windows and doors, you may have come across the name Accoya.
Over the last decade, Accoya has become one of the most talked-about materials in the joinery industry, particularly for high-performance windows and doors. It is often specified for projects where durability, stability and low maintenance are priorities.
At G S Haydon & Son, we are an authorised Accoya manufacturer and have used the material on a wide range of projects across Devon, Exmoor and West Somerset. Whilst we believe Accoya is an exceptional product, we also believe that every property is different and that the most expensive option is not always the most appropriate one.
In this guide, we'll explain what Accoya is, what makes it different from traditional timber, and when it may be the right choice for your project.
What Is Accoya?
Accoya is a modified wood. It begins life as sustainably sourced radiata pine and is then put through a process known as acetylation.
Without becoming too technical, this process permanently modifies the timber at a cellular level, reducing its ability to absorb moisture from the surrounding environment. The result is a timber that is exceptionally stable, highly durable and resistant to decay.
Unlike many timber treatments, acetylation does not rely on toxic preservatives. The finished product remains a natural timber that can be worked, machined, painted and repaired in much the same way as conventional wood.
Accoya carries a manufacturer's warranty of up to 50 years above ground and 25 years in-ground, making it one of the most durable timber products currently available.
Why Does Stability Matter?
One of the biggest challenges for any timber window or door is movement.
Timber naturally expands and contracts as moisture levels and temperatures change. Whilst all timber moves to some extent, excessive movement can lead to problems such as:
- Doors sticking or becoming difficult to close
- Windows becoming harder to operate
- Joints opening over time
- Weather seals becoming less effective
- Paint finishes deteriorating more quickly
This is where Accoya offers a significant advantage.
Because it absorbs far less moisture than conventional timber, it remains remarkably stable throughout the seasons. In practical terms, this helps windows and doors continue to operate smoothly and maintain their weather performance over many years.
Having manufactured windows and doors from a variety of timbers over the years, one of the things we particularly value about Accoya is its consistency. The less a timber moves, the easier it is to achieve long-term weather tightness, smooth operation and durable paint finishes.
The Benefits of Accoya Windows and Doors
Exceptional Durability
Accoya achieves Class 1 durability, the highest rating available for timber.
In practical terms, it offers a level of durability that rivals or exceeds many traditional hardwoods and has demonstrated long-term performance in some of the most challenging environments.
Improved Paint Life
Because the timber remains so stable, paint coatings experience less stress from expansion and contraction.
This can significantly extend maintenance intervals compared to many conventional timber products, helping painted windows and doors remain attractive for longer.
Better Long-Term Performance
The stability of Accoya benefits more than just the paint finish.
Weather seals, glazing systems, joints and ironmongery all tend to perform more consistently when the timber surrounding them remains stable. This contributes to windows and doors that continue to function properly many years after installation.
Sustainability
Accoya is produced from responsibly sourced timber and has strong environmental credentials.
For homeowners looking for a natural, renewable building material with a long service life, it is widely regarded as one of the most sustainable choices available.
Where Does Accoya Work Particularly Well?
Whilst Accoya can be used almost anywhere, it is especially well suited to:
Coastal Properties
Properties exposed to driving rain, salt-laden air and strong winds can place significant demands on external joinery. Accoya's stability and durability make it particularly well suited to these environments.
Exposed Rural Locations
Many properties across Exmoor and North Devon experience harsher weather conditions than urban areas. Accoya can help provide long-term reliability in these exposed locations.
Period and Listed Properties
Where traditional timber appearance is important but owners also want modern levels of durability and reduced maintenance, Accoya often provides an excellent balance.
Large-Format Joinery
Large casement windows, French doors, bi-fold doors and other substantial joinery components benefit greatly from the material's dimensional stability.
Is Accoya Always the Right Choice?
Not necessarily.
One of the conversations we regularly have with clients is whether Accoya is genuinely required for their particular project.
Accoya is undoubtedly an excellent material, but there are many situations where a well-designed and properly maintained hardwood or softwood window will provide decades of reliable service at a lower initial cost.
For example, a sheltered property may not benefit from Accoya to the same extent as a coastal or highly exposed location.
Rather than automatically recommending the most expensive option, we prefer to understand the property, its location and the client's expectations before making a recommendation.
Our role is to help you choose the most appropriate solution for your home, not simply the most expensive one.
Why Choose an Authorised Accoya Manufacturer?
As an authorised Accoya manufacturer, G S Haydon & Son have undertaken the training and approval processes required to manufacture Accoya joinery to the required standards.
Every window and door is individually made to measure in our South Molton workshop by our own team and installed by us throughout Devon, Exmoor and West Somerset.
This provides a single point of responsibility from initial survey through to installation and aftercare.
Thinking About Accoya for Your Project?
If you're considering timber windows or doors for your property and would like impartial advice on whether Accoya, hardwood or softwood is the most appropriate choice, we'd be happy to help.
We have been manufacturing bespoke joinery since 1926 and believe that good advice starts with understanding the property before recommending a material.
Sometimes that recommendation will be Accoya.
Sometimes it won't.
Either way, you'll receive practical advice based on what is best for your home.
G S Haydon & Son Ltd
Established 1926
CERTASS Registered Timber Window and Door Manufacturers and Installers
South Molton, North Devon