Advanced Timber Knowledge

Choosing a Timber Specie for External Seating: Important Considerations

When specifying timber choosing the right species for external seating is a critical decision, especially since outdoor furniture plays a huge role in the creation of extraordinary spaces. When choosing which timber species to specify, you need to weigh factors such as durability, aesthetics, sustainability, and maintenance to ensure your seating not only looks good but meets lifetime expectations.

In this blog, we will explore the key considerations when choosing timber for external seating, along with an analysis of various wood species: UK-grown oak, Douglas fir, Opepe, Iroko, Bamboo, and Accoya. We’ll discuss why some of these options are more suitable than others, and give you the confidence to specify a suitable timber for external seating.

1. Durability and Weather Resistance

The first and perhaps most important consideration when specifying timber for external seating is its ability to withstand outdoor conditions. The timber used outdoors must be resistant to rot, decay, and general weathering.

Durability ratings classify timber on a scale from Class 1 (very durable) to Class 5 (not durable), which helps assess how long the wood will last when exposed to the elements.

Important Note: All natural, untreated timber will develop a silvery grey colour as it dries. Find out why here.

UK-Grown Oak: A popular and traditionally used hardwood, oak is a strong, moderately durable timber (Class 2). It’s well suited to external use and performs well in UK climates. It has a natural resistance to decay, although untreated oak can be prone to splitting and surface checking due to moisture absorption and drying cycles. Over time, oak weathers to a beautiful silvery-grey patina, enhancing its aesthetic appeal for many outdoor settings. See an Oak-featured project here.
Douglas Fir: This is a softwood with moderate durability (Class 3). Douglas fir is widely used in construction for its strength and flexibility, and while not as naturally durable as hardwoods like oak, it can perform well. Douglas Fir also makes an exceptionally sustainable timber choice as it is grown in Plantation Forests in the UK. Its light colour and attractive grain pattern also make it a visually appealing choice for outdoor seating. See Douglas Fir projects here.
Opepe: Opepe is an African hardwood with exceptional durability (Class 1). It is highly resistant to decay, insects, and moisture, making it ideal for outdoor applications. Opepe’s density and natural oils allow it to withstand even the harshest environments with minimal maintenance. While not as commonly available as oak or Douglas fir in the UK, Opepe is a solid option where long-term durability is critical. See an Opepe project here.
Iroko: Often referred to as “African Teak,” Iroko is another highly durable timber (Class 1). Like Opepe, it has a natural resistance to decay and insects, making it a top choice for external seating. Iroko is known for its rich golden-brown colour, which eventually fades to a silvery-grey when exposed to the elements. It requires minimal maintenance and offers excellent long-term performance, making it one of the most reliable hardwoods for outdoor furniture. See Iroko projects here.

2. Sustainability

With growing awareness of environmental issues, the sustainability of timber is an important consideration when specifying timber. Opting for responsibly sourced timber can reduce environmental impacts, protect ecosystems, and promote sustainable forestry practices.

UK-Grown Oak: One of the most sustainable choices is UK-grown oak. By choosing locally sourced timber, you minimize the carbon footprint associated with transportation. Oak from sustainably managed forests, certified by organizations such as the Forest Stewardship Council (FSC) or the Programme for the Endorsement of Forest Certification (PEFC), ensures that timber is harvested responsibly. The use of homegrown timber also supports local industries and reduces reliance on imported wood.
Douglas Fir: Like oak, Douglas fir can be sustainably sourced from well-managed UK and European forests. It’s a renewable resource with a faster growth rate than most hardwoods, making it an eco-friendly choice. Look for FSC certification when sourcing Douglas fir to ensure it comes from responsible forestry practices.
Opepe and Iroko: Both of these species are tropical hardwoods, typically imported from Africa. While they are highly durable and long-lasting, their environmental impact can be significant due to deforestation concerns and the distance they must travel. However, if you opt for FSC-certified Opepe or Iroko, you can ensure that the timber is harvested from sustainably managed forests, reducing the negative environmental impact.
Bamboo and Accoya: Although marketed as eco-friendly options, both bamboo and Accoya have environmental drawbacks that limit their suitability for external seating. More on these below.

3. Maintenance Needs

Understanding the maintenance requirements of different species is essential when specifying timber. Different timber species require varying levels of maintenance to keep them in top condition. Maintenance requirements should factor into your decision, especially if you’re looking for a low-maintenance solution.

UK-Grown Oak: Oak benefits from periodic maintenance to ensure longevity. Regular oiling or the application of a water-resistant finish can help protect it from moisture and UV damage, preventing cracking and warping. While oak can weather naturally without treatment, it may develop surface splits over time if left untreated in harsh climates.
Douglas Fir: Douglas fir needs more frequent maintenance due to its lower natural resistance to decay. A protective finish or regular oiling is essential to prevent moisture penetration, especially in wet climates. When well-maintained, Douglas fir can last for many years in external applications.
Opepe and Iroko: These hardwoods require very little maintenance due to their high natural resistance to decay and pests. If left untreated, they will weather to an attractive grey patina over time. Occasional oiling can help preserve the wood’s natural color, but it’s not essential for the structural integrity of the wood.

4. Aesthetic Appeal

The visual appeal of the timber can significantly influence your choice when specifying timber, especially when creating seating that fits the style and design of your outdoor space. Each timber species has its unique colour, grain, and texture.

UK-Grown Oak: Oak’s warm tones and tight grain pattern make it a popular choice for both traditional and contemporary designs. Its appearance only improves with age as it takes on a silvery patina, giving the seating a timeless, rustic look.
Douglas Fir: With its light reddish hue and straight grain, Douglas Fir is aesthetically pleasing, especially for modern or minimalist designs. It also takes finishes and stains well, giving you flexibility in customizing its look.
Opepe and Iroko: Both Opepe and Iroko boast rich, warm colours ranging from golden yellow to dark brown. Their dense, attractive grain patterns make them a desirable option for upscale outdoor seating. Over time, these woods will naturally weather to a grey finish unless regularly oiled.

5. Bamboo and Accoya

Bamboo: Bamboo is fast-growing and renewable, but it’s not a timber—it’s grass. Bamboo furniture, while eco-friendly, lacks the long-term durability of hardwoods like oak or Iroko. In external applications, bamboo can degrade quickly when exposed to moisture and temperature fluctuations. Although treated bamboo products may resist weathering to some extent, they are not as reliable as hardwoods for outdoor seating and may require frequent maintenance or replacement.
Accoya: Accoya is a chemically modified softwood designed for enhanced durability and stability. While Accoya is highly resistant to decay, its chemical modification process, which uses acetic anhydride to alter the wood’s structure, raises concerns for those seeking a more natural product. Accoya’s unique aesthetic may not be perfect for many projects and its cost can be prohibitive for many projects.

Conclusion

When specifying timber choosing the right species for external seating involves balancing multiple factors, from durability and maintenance to sustainability and aesthetics. UK-grown oak, Douglas fir, Opepe, and Iroko are excellent choices for outdoor furniture due to their varying degrees of durability, aesthetic appeal, and sustainability. Each of these timbers offers a unique set of benefits that can suit different project requirements and design preferences.

In the end, selecting timber that meets the project needs and personal preferences will ensure that your external seating stands the test of time.

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