One of the most common questions we receive at A&J Joinery is: "What is Accoya, and is it really worth paying more for?" If you are considering bespoke sash window replacement for a Fulham period property, this is one of the most important decisions you will make — because the answer directly affects how long your windows last, how much maintenance they require and what you spend over the next 20 years.
Here is our honest guide as the joinery company that recommends and installs Accoya across Fulham, Chelsea, Hammersmith and all of South West London.
What is Accoya Timber?
Accoya is a modified wood produced from sustainably grown radiata pine. The modification process — called acetylation — permanently changes the cell structure of the timber by replacing the wood's reactive hydroxyl groups with acetyl groups. This makes the wood:
- Dimensionally stable — it barely moves with seasonal moisture changes, unlike conventional softwood which swells and shrinks significantly
- Extremely durable — resistant to rot, fungal attack and insect damage
- Low maintenance — holds paint far better than conventional softwood; repainting intervals extend to 8–12 years vs 4–6 years for standard pine
- Thermally efficient — Accoya has significantly better thermal insulation than most hardwoods
- Sustainably produced — FSC certified, non-toxic, fully biodegradable
The manufacturer's guarantee is 50 years above ground against rot — remarkable for a timber window in London's variable climate.
"Accoya eliminates the biggest long-term cost of timber sash windows — rot repair and premature replacement. For Fulham period properties, it is the best-value timber over a 20-year horizon."
Accoya vs Softwood vs Hardwood — How Do They Compare?
Timber Comparison for Sash Windows — Fulham (2026)
Softwood
Cost per window (supply & fit)£900 – £1,800
Expected lifespan (well maintained)25 – 40 years
Repainting intervalEvery 4 – 6 years
Rot riskModerate – High
Hardwood (idigbo/oak)
Cost per window (supply & fit)£1,500 – £2,800
Expected lifespan (well maintained)40 – 60 years
Repainting intervalEvery 5 – 8 years
Rot riskLow – Moderate
Accoya® (Recommended)
Cost per window (supply & fit)£1,800 – £3,200
Expected lifespan50+ years (guaranteed)
Repainting intervalEvery 8 – 12 years
Rot riskNegligible (50yr guarantee)
Why A&J Joinery Recommends Accoya for Fulham
We recommend Accoya as our first choice for most Fulham sash window replacements for five specific reasons:
- Fulham's climate — London's rain and humidity are hard on exposed softwood. North-facing elevations and ground-floor windows in Fulham's terraces often see rot within 15 years in softwood
- Dimensional stability — Accoya's minimal movement means draught-proof seals stay effective for longer, and sashes continue to slide smoothly year-round without seasonal sticking
- Conservation area compliance — Accoya finishes identically to softwood and is accepted by all London conservation officers as an appropriate material
- Long-term cost — over 20 years, the savings on repainting, rot repair and delayed replacement typically exceed the upfront premium
- The guarantee — a 50-year manufacturer's guarantee against rot on a window component is unprecedented. It is the only timber we can install with complete confidence for the long term
Interested in Accoya sash windows for your Fulham home?
Free survey, no obligation. Written quote within 48 hours.
Is Accoya Right for Your Property?
Accoya is the right choice if:
- Your property has an exposed or north-facing elevation
- You have experienced rot in previous timber windows
- You want to minimise maintenance commitments over the next 20+ years
- You are planning to stay in your property long-term
- You want the security of a 50-year manufacturer's guarantee
Softwood may be more appropriate if budget is the primary constraint and the windows are in a sheltered position with regular maintenance planned. A&J Joinery will give you an honest recommendation during your free survey based on your specific property's exposure, orientation and maintenance history.
