When selecting timber for external doors and windows, choosing the right material impacts performance, longevity, and maintenance costs. Two premium options dominate the UK market: Accoya wood and Red Grandis timber. But which timber species delivers the best value for your project?
At DAB Doors, we work with both Accoya and Red Grandis for windows and doors. This comprehensive guide compares these leading hardwood timber species across durability, cost, sustainability, and performance to help you make an informed decision.
What is Accoya Wood?
Accoya is a modified timber produced through an innovative process called acetylation. Starting with sustainably sourced radiata pine from FSC-certified forests, the wood undergoes molecular modification that transforms its natural properties.
The Acetylation Process Explained
The acetylation process involves treating timber with acetic anhydride, which modifies the wood’s cell structure at a molecular level. This chemical modification replaces free hydroxyl groups within the wood, reducing its ability to absorb water by approximately 80%. The result is acetylated wood modified right through to its core, not just surface-treated.
Importantly, acetylation doesn’t introduce toxic chemicals. It simply increases levels of compounds already naturally present in wood. The only byproduct is acetic acid (vinegar), which is collected and reused or sold.
Key Benefits of Accoya Timber
Class 1 Durability Rating: Accoya holds a Class 1 durability classification, the highest rating available. It surpasses even the most durable tropical hardwoods like teak, with a guaranteed lifespan of 60+ years above ground when properly maintained. With sensible coating cycles, Accoya’s lifespan can potentially extend indefinitely.
Exceptional Dimensional Stability: One of Accoya’s standout features is its remarkable stability in timber. It resists swelling, shrinking, and warping even in extreme weather conditions or high humidity environments. This exceptional stability means doors and windows maintain their precise fitting throughout the seasons, preventing drafts and ensuring smooth operation year-round.
Superior Coating Performance: Thanks to its stability, coatings on Accoya timber last up to twice as long as on conventional timber. Paint and stain finishes remain intact longer, reducing maintenance frequency and costs.
Outstanding Thermal Insulation: Accoya for windows offers superior thermal insulation compared to other hardwoods and softwoods, helping to improve energy efficiency and reduce heating and cooling costs.
Environmentally Responsible: Made from fast-growing, sustainably managed radiata pine that can be harvested after 30 years, Accoya is FSC-certified timber and has achieved Cradle to Cradle Gold certification. The wood is fully recyclable, biodegradable, and non-toxic.
Complete Rot and Insect Resistance: The acetylation process makes Accoya wood unrecognizable as a food source to insects and fungi, providing complete protection without the need for toxic preservatives.
What is Red Grandis Timber?
Red Grandis is a premium quality hardwood timber from the Eucalyptus grandis species, native to Australia’s east coast but now grown primarily in FSC-certified plantations in Uruguay. This plantation-grown timber has emerged as a sustainable alternative to slower-growing tropical hardwoods.
How Red Grandis is Produced
Red Grandis trees are carefully managed throughout their growth cycle. The trees are spaced, pruned, and thinned multiple times to produce tall, straight trunks with minimal knots. After 20-30 years of growth, when the trees reach 40-70 meters in height and 60-70cm in diameter, they’re harvested and processed into engineered timber products.
The timber is supplied as engineered Red Grandis, with laminated sections featuring alternating grain patterns. This manufacturing process enhances dimensional stability and reduces waste compared to rough-sawn timber, making it quicker to process and more consistent in quality.
Key Benefits of Red Grandis for Windows and Doors
Class 3 Durability: Red Grandis is classified as Class 3 (Moderately Durable) timber. Independent testing by TRADA Institute has demonstrated it can last 30 years without treatment, and with proper coating and maintenance, Red Grandis doors and windows can achieve a service life exceeding 50 years.
Exceptional Strength: Despite being a relatively fast-growing species, Red Grandis hardwood has strength properties comparable to European oak, making it suitable for structural applications and large-span components like door frames.
Superior Workability: Red Grandis is easy to machine, glue, stain, and finish. Its dense, straight-grained structure with minimal knots provides excellent edge retention and resists denting better than softer timbers. This results in precise joinery and a superior paint finish.
Attractive Natural Appearance: The timber features a uniform grain with attractive colour tones ranging from pale pink to reddish-brown. This consistent appearance makes it ideal for both painted and stained finishes, and it can be easily stained to resemble oak, sapele, or mahogany.
Carbon-Negative Timber: Red Grandis is 100% FSC-certified and carbon-negative at the raw material stage, absorbing more CO2 during its 20-year growth cycle than is emitted during processing. The engineered manufacturing process maximizes material use and minimizes waste.
Cost-Effective Premium Timber: Red Grandis offers premium performance at a more accessible price point than Accoya or traditional hardwoods like oak, making it an economical choice for high-quality timber joinery projects.
Excellent Finish Retention: Thanks to its smooth, dense surface, Red Grandis accepts factory-applied microporous coatings exceptionally well. The finish remains even and intact for longer periods, reducing maintenance requirements.
Accoya vs Red Grandis: Direct Comparison
Durability Comparison
Winner: Accoya
Accoya’s Class 1 durability rating gives it the edge over Red Grandis’s Class 3 classification. While Red Grandis will reliably last 50+ years with proper maintenance, Accoya can potentially last 60+ years or even indefinitely with appropriate care. For projects in extremely harsh coastal environments or locations with severe weather exposure, Accoya’s superior rot resistance provides additional peace of mind.
However, Red Grandis’s 50+ year lifespan still represents excellent value and more than adequate performance for most residential and commercial door and window applications.
Dimensional Stability
Winner: Accoya
Accoya’s acetylation process delivers unmatched dimensional stability for timber. Its resistance to moisture absorption means minimal movement throughout seasonal changes, even in extreme conditions. This translates to:
- Doors and windows that open and close smoothly all year round
- Reduced risk of warping, bowing, or twisting
- Better performance for insulating glass units
- Less stress on coatings and finishes
Engineered Red Grandis offers good stability, particularly in its laminated form, but cannot quite match Accoya’s performance in environments with significant temperature and humidity fluctuations.
Sustainability and Environmental Impact
Winner: Tie (with different strengths)
Both timbers offer excellent sustainable timber credentials, but in different ways:
Accoya:
- FSC-certified from sustainably managed forests
- Non-toxic and fully recyclable
- Cradle to Cradle Gold certified
- Long lifespan reduces replacement frequency
- Made from fast-growing pine (30-year cycle)
Red Grandis:
- 100% FSC-certified timber
- Carbon-negative at raw material stage
- Faster growth cycle (20 years vs 30 for Accoya source pine)
- Prevents illegal logging by providing regulated employment
- Efficient engineered processing minimizes waste
For those prioritizing carbon-negative materials, Red Grandis has a slight edge. For those focused on overall lifecycle sustainability, Accoya’s exceptional longevity is compelling.
Cost and Value
Winner: Red Grandis
Red Grandis timber price is significantly more affordable than Accoya, typically costing a fraction of the price. This makes it accessible for projects with tighter budgets while still delivering premium performance. The cost advantage of Red Grandis makes it comparable in price to traditional options like sapele or idigbo, but with better sustainability credentials.
Accoya commands a premium price, but its superior durability and lower maintenance requirements can offset the higher initial investment over the timber’s lifespan.
Maintenance Requirements
Winner: Accoya
Both timbers require periodic maintenance, but Accoya’s superior stability means coatings last approximately twice as long as on conventional timber. This translates to:
- Less frequent repainting or re-staining
- Lower long-term maintenance costs
- Reduced disruption from maintenance work
Red Grandis requires more regular coating maintenance than Accoya, though still less than traditional softwoods. Factory-applied microporous coatings help maximize coating lifespan on Red Grandis.
Workability and Aesthetics
Winner: Red Grandis
Red Grandis excels in workability. It machines beautifully, holds edges well, and produces minimal waste thanks to its knot-free, straight-grained structure. For joinery manufacturers, this translates to faster processing and superior finish quality.
Both timbers accept stains and paints well, though Red Grandis’s natural pink-to-red tones offer more aesthetic flexibility for stained applications. Accoya retains a pale colour similar to its source pine species.
Thermal Insulation Performance
Winner: Accoya
Accoya offers superior thermal insulation properties compared to conventional hardwoods and softwoods, including Red Grandis. This contributes to better energy efficiency, helping to reduce heating and cooling costs in your home.
Which Timber Should You Choose for Your Project?
Choose Accoya Timber If:
- Your project requires maximum durability and longevity (60+ years)
- The installation faces extreme weather exposure or coastal conditions
- Dimensional stability is critical (e.g., large glazed units, precision fitting)
- You want to minimize long-term maintenance requirements
- Budget allows for premium timber materials
- You prioritize thermal performance for windows
- The project demands the highest rot and insect resistance
Choose Red Grandis Timber If:
- You’re working with a tighter budget but still want premium performance
- A 50+ year lifespan meets your project requirements
- You prioritize carbon-negative, rapidly renewable materials
- You want excellent workability and finish quality
- The timber won’t face extreme environmental conditions
- Cost-effectiveness is a primary concern
- You appreciate the natural pink-red aesthetic
Accoya vs Red Grandis: Final Verdict
Both Accoya and Red Grandis represent excellent choices for high-quality timber doors and windows, far superior to conventional softwoods or compromised hardwoods. Your choice ultimately depends on your specific priorities:
For ultimate performance and longevity: Accoya is unrivaled. Its Class 1 durability, exceptional stability, and minimal maintenance make it the premium choice for the most demanding applications.
For outstanding value and sustainability: Red Grandis offers premium performance at a more accessible price point. Its 50+ year lifespan, carbon-negative status, and excellent workability make it ideal for most residential and commercial projects.
At DAB Doors, we work with both timbers and can advise on the best timber choice for your specific project requirements, location, budget, and aesthetic preferences. Both materials will deliver beautiful, long-lasting results when properly manufactured and installed.
Making Your Timber Decision: Key Questions
Consider these questions when choosing between Accoya and Red Grandis:
- What’s your budget? If cost is a significant factor, Red Grandis delivers excellent value.
- How long do you need the timber to last? Both offer 50+ years, but Accoya can extend beyond 60 years.
- What are your environmental priorities? Red Grandis is carbon-negative; Accoya offers exceptional longevity.
- How much maintenance can you commit to? Accoya requires less frequent recoating.
- What are the site conditions? Extreme exposure or coastal locations favor Accoya.
- What aesthetic do you prefer? Red Grandis offers warmer natural tones; Accoya is lighter.
Get Expert Advice on Timber Selection
Still unsure which timber is right for your doors and windows project? Contact DAB Doors today. Our experienced team can provide samples, discuss your specific requirements, and recommend the perfect timber solution for your doors and windows. With decades of expertise in premium timber joinery, we’re here to ensure your project exceeds expectations for beauty, performance, and longevity.
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- Sustainable Timber Choices for Your Home
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