Selecting the right timber is one of the most important decisions when commissioning sash windows. It influences how the frame looks, how long it lasts, and how well it resists the elements. Two timbers often compared in the market are Red Grandis and Accoya.
What is Red Grandis?
Red Grandis is a plantation-grown hardwood prized for its strength and appearance. When engineered for joinery, multiple layers of defect-free Red Grandis are laminated together. This process enhances dimensional stability, reducing the risk of warping or twisting over time, while maintaining the tactile qualities of natural hardwood.
Its fine, even grain and warm reddish tones give Red Grandis a consistently appealing look. Unlike many tropical hardwoods, it contains no knots or resin pockets, meaning it requires minimal preparation before finishing – whether painted in a heritage shade or stained to highlight its natural character.
Beyond performance and appearance, Red Grandis also stands out for its sustainability. Grown on FSC®-certified plantations in Uruguay, every tree harvested is replanted. These fast-growing forests capture significant amounts of carbon, making the timber both renewable and environmentally responsible.
What is Accoya?
Accoya is a softwood, typically radiata pine, that has been chemically modified through a process called acetylation. This treatment alters the timber at a molecular level, making it exceptionally stable and highly durable outdoors. It is often used in windows and doors because it resists swelling, shrinking, and decay better than many traditional woods.
However, Accoya is not a natural hardwood. Its pale, almost white colour lacks the grain depth and warmth of species like Red Grandis, which can make it less suited to period-style joinery where authenticity matters. While it offers strong performance, some homeowners prefer timbers that provide durability with a natural appearance.
Key Comparisons
The Look of the Timber
Red Grandis is a true hardwood, with a fine, even grain and a naturally warm tone. It looks and feels like traditional hardwood, making it well-suited to heritage-style sash windows. Accoya, by contrast, is a modified softwood with a pale, almost washed-out colour that lacks the same natural depth.
How Each Timber Takes a Finish
Red Grandis accepts both paint and stain exceptionally well, producing a smooth, uniform surface with minimal preparation. Accoya’s softer, more open texture often requires extra coats or preparation to achieve the same level of finish, particularly with darker or heritage colour schemes.
Precision in Craftsmanship
Because it is engineered hardwood, Red Grandis machines cleanly and holds fine profiles such as horns, beads, and glazing bars. Accoya, being fibrous and softer, can feather under tools, which makes it less precise for detailed joinery.
Performance in Use
Both timbers perform well in terms of stability. Red Grandis achieves this through engineered lamination, which resists warping or twisting over time. Accoya’s stability comes from its acetylation process, which chemically alters the wood to reduce movement.
Longevity and Natural Strength
Red Grandis is naturally durable, delivering long service life without the need for chemical modification. Accoya also performs well outdoors, but only because of its treatment process. For homeowners who value timber in its natural state, Red Grandis offers durability without synthetic alteration.
Environmental Considerations
As mentioned, Red Grandis is plantation-grown in FSC®-certified forests in Uruguay. Accoya is also FSC®-certified, but its acetylation process introduces additional industrial steps, raising questions about embodied energy and end-of-life recycling.
Why Sash Windows London Chooses Red Grandis
Red Grandis has become the preferred timber for many of our window and door projects. As an engineered hardwood, it provides the rigidity needed for sash frames while delivering the refined look expected in period-style properties across London and the South East.
Considerations for Homeowners
Both Red Grandis and Accoya perform well as timbers for windows and doors, though they differ in appearance, sourcing, and how they are manufactured. For many, the choice comes down to whether a natural hardwood look is preferred, how important sustainability credentials are, and the character of the property itself.
Working with Sash Windows London, we review each project on a case-by-case basis, ensuring the timber selected suits heritage requirements, planning restrictions, and individual style preferences.
Making the Right Timber Choice
Ready to discuss timber sash windows for your property?
Red Grandis stands out as a modern hardwood that delivers lasting strength and authentic character. For homeowners in the UK, it offers a premium solution. To explore whether Red Grandis is the right fit for your property, get in touch with our team today.
