Woods generally are a sustainable material thanks to their carbon sequestration. However, their environmental impacts vary based on the specific trees, their biodiversity, and their distance and method of transportation. Besides, some sought-after decking wood comes from tropical rainforests where illegal logging has devastating consequences on the earth’s biodiversity. So we have to ask: Which woods are the most sustainable for decking?

The most sustainable decking woods are redwood, western red cedar, Nootka cypress, pine, douglas fir, and bamboo. These timber trees are fast-growing species with sustained populations. Some sustainably harvested tropical woods can make environmentally friendly decks because of their durability. 

In this article, we will walk you through the life-cycle of the six most sustainable woods used in outdoor decks. Then, we evaluate its sustainability, potential, and shortfalls. We will also investigate a few tropical hardwoods that could be sustainable decking options providing responsible harvesting. And in the end, we’ll show you tips for buying sustainable woods.

Here’s How We Assessed the Sustainability of All Types of Wood for Decking

In general, wood is a sustainable material because of timber trees’ carbon sequestration potential and the carbon offset value at the end of the wood product’s life-cycle. 

“Sustainable: The ability to be maintained at a certain rate or level | Avoidance of the depletion of natural resources in order to maintain an ecological balance”

Oxford Dictionary

However, some woods are better than others for building a sustainable deck outside. One way of assessing the sustainability of wooden decks is to go through their life-cycles and assess each stage’s sustainability. This life-cycle assessment (LCA) is a method to evaluate the environmental impacts of products and materials. Over the years, companies have strategically used LCA to research and create more sustainable products. So, let’s have a look at the LCA of some most sustainable hardwoods!

In this article, we’ll use the cradle-to-grave perspective of the LCA, examining the five stages of the life-cycle of woods used for outdoor decks. Where it is relevant, we also use data from cradle-to-gate assessments. 

These five stages of the life-cycle of a wooden deck are as follows:

1. Growing of the wood
2. Manufacturing of the wooden panels for decking
3. Transportation of the wooden panels
4. Usage of the wooden deck
5. End-of-life of the wooden deck

The life-cycle assessment typically covers some or all of the following environmental impacts:

• Global warming potential 
• Primary energy demand from resources 
• Acidification potential
• Freshwater eutrophication potential 
• Marine eutrophication potential 
• Photochemical ozone creation potential 
• Resource depletion

The global warming potential impact reflects the risk of accelerating climate change through the emissions of greenhouse gases. It focuses on CO₂ and other greenhouse gasses (CH₄, nitrous oxide, and chlorofluorocarbons) released throughout a product’s life-cycle. This impact is measured in kg of CO₂ equivalent emitted per unit of a product – the carbon footprint. 

“Carbon footprint: the amount of greenhouse gases and specifically carbon dioxide emitted by something (such as a person’s activities or a product’s manufacture and transport) during a given period”

Merriam Webster

Deciding factors for a high or low carbon footprint in wooden decking are: 

• Drying requirements of decking timber
• Distribution of timber trees 

Because of the tree’s carbon sequestration potential, the carbon emitted during various stages of a wooden deck’s life cycle can be compensated by the carbon captured and stored. The deciding factors for high or low carbon storage in wooden decks are: 

• Tree sizes 
• Tree growth rate 
• Natural durability 

In this article, we cover six woods that are the most decking material regarding their global warming potential. We will also look into how to make a more sustainable choice when using tropical hardwoods for your outdoor decks. We’ll zoom into species’ growth rate, tree size, distribution, woodworking properties, and natural durability, as these are the deciding reasons behind the carbon balance of wooden decks. 

These Are the Six Most Sustainable Types of Wood for Decking

These woods have, to some extent, natural resistance to rot and decay, making them durable decking materials. They also have low carbon emissions on a life-cycle assessment basis. 

Overall, these woods are highly sustainable. However, the actual environmental impact of a wooden deck depends on many factors, especially the distance and mode of transportation. Let’s dive deeper into each wood and the stages of its life-cycle and find out how it can be more sustainable. 

Redwood: Durable Decking Material from Fast-Growing Giant Conifers 

Redwood comes from coastal redwood trees – the tallest living trees on earth. These giant conifers provide plenty of timber. Also, their timber is the strongest natural decking material from US forests. 

Here are the life-cycle stages of redwood and each stage’s sustainability assessment:

• Growing of redwood: Coastal redwood trees (Sequoia sempervirens) grow at a fast rate of 3 feet per year. They act as a carbon sink during their long lifespan of over 2,000 years, helping to mitigate the climate crisis. The species’ ability to regrow from sprouts is significant in reforesting ancient woodlands while replenishing the timber source. 
• Manufacturing of redwood: Because redwood is exceptionally stable, it can often be used in green form for decking projects. Alternatively, redwood lumber is air-dry first to minimal kiln-drying time and energy. Therefore, the drying carbon footprint of redwood decking, on average, is much lower than other wooden decks.   
• Transportation of redwood: Redwood trees grow extensively along the West Coast of the US. Thus, the transporting carbon footprint to states such as California, Colorado, Utah, Nevada, or Arizona is relatively low. Less energy is expended in shipping redwood around these regions compared to importing tropical hardwoods, such as mahogany or teak. 
• Usage of redwood: This timber is extremely resistant to rot, weather, insects, fungi, and even fire as it is high in tannin and does not produce resin or pitch. An untreated, natural redwood deck could last for two to three decades. That is two to three decades of carbon storage: 100 square feet of redwood decking (used for 25 years) stores –262 kg CO₂-eq.
• End-of-life of redwood: Redwood can either be up-cycled to lengthen the carbon storage role or burned biomass energy displacing coal or natural gas to generate electricity. Both scenarios are sustainable. 

Redwood is a highly sustainable material when it comes to outdoor decking. The tall trees sequester significant amounts of carbon. At the same time, redwood decks keep the captured carbon out of the atmosphere for the many years they last. 

Besides, manufacturing redwood decking has relatively low carbon emissions thanks to little need for using a kiln to dry this dimensionally stable timber. (Kiln-drying is usually the most energy-intensive process for wood products.) 

These two factors combine and result in a negative carbon balance in redwood decking (-163 kg CO₂-eq).

Western Red Cedar Wood: Light Decking Material With Low Transporting Carbon Footprint 

Western red cedar is timber from the tall and big conifers that grow in abundance in the US – the giant arborvitae. This timber is highly available. Plus, its natural properties make it a long-lasting material for decking, more durable than many US softwoods and hardwoods. 

Here are the life-cycle stages of western red cedar wood and each stage’s sustainability assessment:

• Growing of cedar wood: Western red cedar (Thuja plicata) trees have a high carbon sequestration potential thanks to their large sizes (200 feet in height and 4 feet in diameter) and their long lifespan (over 1,000 years). In North America, western red cedar trees are abundant and sustainably managed. Thus, timber harvesting doesn’t harm the forests.
• Manufacturing of cedar wood: Western red cedar is dimensionally stable; thus, less energy is wasted on shrinkage, checking, and warping during kiln-drying. 
• Transportation of cedar wood: Western red cedar trees are abundant in the Northwest US. In states such as Washington, Oregon, or Idaho, it’s possible to source western red cedar locally, lowering the transportation footprint. Also, transporting this lightweight timber is more fuel-efficient than hauling heavy hardwoods. Consequently, transporting carbon footprint per unit is smaller. In a case study, the carbon footprint of transporting 100 feet of western red cedar decking to customers within Minneapolis is 18.25 kg CO₂-eq. 
• Usage of cedar wood: Because western red cedar has excellent rot and pest resistance, decks made with this timber can last for two decades without needing any protective stain. Such long-lasting products are a good way to keep carbon out of the atmosphere.  
• End-of-life of cedar wood: The end-of-life stage for cedar decking is sustainable because the wood can be fully reused or burned as bioenergy. 

The net carbon balance of 100 square feet of no-stain western red cedar decking is -13.39 kg CO₂-eq (cradle-to-grave). The negative balance is thanks to carbon sequestration during the forestry stage. Also, cedar timber has a relatively low transporting carbon footprint because it is light and available locally within the US. 

Nootka Cypress Wood: Durable Decking Material from Native Conifer Species

Nootka cypress wood comes from medium-size, long-lived conifers native to the west coast of North America. This Cupressus nootkatensis species belongs to the Cypress family but is also commonly called a cedar, as in Alaska yellow cedar or yellow cedar. 

Here are the life-cycle stages of Nootka cypress wood and each stage’s sustainability assessment:

• Growing of Nootka cypress wood: As Nootka cypress trees grow, they absorb CO₂ from the atmosphere while releasing oxygen. They act as a carbon sink during their long lifespan (as long as 3,500 years), helping to mitigate the climate crisis. 
• Manufacturing of Nootka cypress wood: Nootka cypress is another stable softwood in this list, with little tendency to warp and check while drying. It takes four and a half days to kiln dry 1-inch timber to a 7% moisture content. 
• Transportation of Nootka cypress wood: Along the west coast, it’s possible to source Nootka cypress wood, lowering the transportation footprint. 
• Usage of Nootka cypress wood: Nootka cypress is highly durable, thanks to the heartwood’s chemical compounds that inhibit fungal growth. It has excellent decay resistance and is also resistant to most insect attacks. Regarding strength, it is among the strongest US softwoods (comparable to Douglas fir), making it an ideal material for heavy-traffic decking. 
• End-of-life of Nootka cypress wood: Because of its natural durability, the wood is seldom treated with preservatives. Thus, Nootka cypress decking can be fully recycled or burned for bioenergy. Both scenarios are sustainable. 

Nootka cypress is a sustainable decking material because of its excellent stability, strength, and decay resistance. Decks made with this material can last for a long time, keeping the carbon stored from being released back into the atmosphere. 

Pine Wood: Highly Available Decking Timber From Sustained Conifer Populations

Pine wood is highly available in the US because of these species’ high population and wide distribution. (One in four American cone-bearing trees is a pine.) Though pine timber is not as rot-resistant as redwood, western red cedar, and Nootka cypress, it can be treated to last longer outside. Thus, it stores carbon longer (instead of releasing carbon back into the atmosphere).  

Here are the life-cycle stages of pine wood and each stage’s sustainability assessment:

• Growing of pine wood: Pine has a sustainable population throughout the US, north and south, east and west. They adapt and thrive under a wide variety of soil and climate. Some pine species, like eastern white pine, grow rapidly, adding 2ft to 3ft per year. Thus, it is possible to harvest pine timber without harming the forests. 
• Manufacturing of pine wood: Pine species dry faster than most hardwoods but slower than some softwood species like Engelmann spruce or western larch. (It takes 30 to 150 days to air dry green 25-mm lumber of southern pine to 20% moisture content.). Because kiln drying is usually the most energy-intensive and carbon-heavy process for wood products, fast-drying wood has a lower carbon emission. 
• Transportation of pine wood: As pine trees are distributed widely in the US, the transporting footprint of pine decking is relatively small, especially when compared with tropical hardwood decking. 
• Usage of pine wood: While pine timber is used as decking, it continues to store carbon (instead of releasing CO₂ back into the atmosphere). The longer the lifespan of a pine decking, the more sustainable this usage stage is. 
  
  Solid pine heartwood is rated as little to moderate durable for outdoor application. However, treated pine can be moderate to highly long-lasting in outdoor projects. 
  
  Chemical-modified pine can be as durable as teak and more than western cedar. For example, a deck made with acetylated radiata pine (chemically treated pine under the Accoya process) can have an average lifespan of 25 years. That is the same lifespan as a deck made with old-growth teak and wood plastic composite. 
  
  Pressure-treated pine – pine impregnated with some chemicals and treated under pressure – also makes durable decking material. However, there are concerns over toxins in arsenic-based chemicals previously used to impregnate pine decking.  

• End-of-life of pine wood: Natural pine decking can be disposed of sustainably in biomass or upcycling projects. 

Pine is one of the most common types of softwoods used for decking because of the availability of this timber regarding both volume and transporting distance. 

Untreated pine heartwood is moderately durable, but because pine is prone to insects. However, it is often treated for outdoor projects – and treated pine decks last significantly longer.

However, unlike other natural wood decking on this list, the carbon balance in treated pine decking is not negative (0.04 kg CO₂-eq per Accoya Slots Pine decking).

Douglas Fir: Strong Decking Material From Widely Distributed Softwood Species

Douglas fir wood comes from one of the tallest tree species on the North American continent. This tree species grows across the largest portion of Western North America, accounting for a fifth of North America’s total softwood reserves. 

Here are the life-cycle stages of Douglas fir wood and each stage’s sustainability assessment:

• Growing of Douglas fir wood: The high carbon sequestration potential makes growing Douglas firs for timber sustainable. In old-growth forests, these tree species can grow as tall as 250 feet and as big as six feet in diameter. The record for Douglas fir height is 330 feet, more than double the height of a tall black walnut tree. The annual growth rate of Douglas fir is up to 2 feet, higher than that of hardwoods frequently used for decking. 
• Manufacturing of Douglas fir wood: Douglas fir lumber can be air-dried from green to a 20% moisture content. The drying time varies significantly depending on the season and location (20 to 200 hours). Using a kiln takes about 32 hours to dry 1/8 inch-sized Douglas fir lumber from green to 15% moisture content. 
• Transportation of Douglas fir wood: Douglas fir trees are distributed widely in the US: they populate the largest section of western states. Consequently, transporting carbon footprint is relatively low, especially compared with popular imported hardwoods for decking like ipe or meranti. 
• Usage of Douglas fir wood: Douglas fir is one of the strongest Western softwood species. It is twice as hard per square inch as cedar and, thus, a possibly longer-lasting choice for heavy-traffic decking. Untreated Douglas fir garden decking can last 10 to 15 years, thanks to this species’ natural resistance to decay. Douglas fir is, however, susceptible to insect attacks. Thus, ACQ pressure treatment is sometimes used. In this case, the deck lifespan could reach 30 or more. 
• End-of-life of Douglas fir wood: The end-of-life stage for untreated Douglas fir decking is sustainable when the wood is reused or burned as bioenergy.

Douglas fir makes beautiful and long-lasting decking. These coniferous trees grow relatively fast and extremely tall, quickly replenishing timber cut for decking, furniture, or construction projects. Also, as a softwood, Douglas fir is harder than most, making it last longer as carbon storage than most other softwoods. 

Bamboo “Wood”: Light Decking Material from Rapid-Growing Species 

Bamboo “wood” is highly sustainable because the bamboo grass plant grows and regrows rapidly, producing 35% more oxygen than a tree with an equivalent mass. Though bamboo is technically not wood (not from a tree), this material has been utilized in many woodworking projects because of its strength and many other beneficial properties. 

Here are the life-cycle stages of bamboo wood and each stage’s sustainability assessment:

• Growing of bamboo wood: Growing bamboo for “wood” is sustainable because of its quick growth rate, the short time to maturity (compared to wood), and its ability to self-propagate. Mature bamboo can be harvested sustainably after three to five years of planting. Better yet, if the roots are left undisturbed, the plant can regrow very quickly without any other inputs but water and sunlight. Last but not least, one acre of bamboo can absorb around 10,000 lbs of carbon dioxide per year.
• Manufacturing of bamboo wood: Manufacturing is the biggest carbon emitter in bamboo “wood” production, mainly due to the energy-intensive drying step. For an  industrial three-layer laminated bamboo board produced in a factory in China, the manufacturing step accounts for 75% of the product’s CO₂ emissions.
• Transportation of bamboo wood: The main sources of valuable commercial bamboo are China and Latin America. It means long traveling distances from forestry to customers in the US. However, bamboo is lightweight. One truck can carry much more bamboo panels than, for example, teak logs. The weight tends to compensate for the distance, leaving bamboo one of the sustainable decking choices. 
• Usage of bamboo wood: Bamboo is more durable than traditional hardwoods. It’s stronger than steel and more resistant to water, infestation, rotting, and warping than hardwoods. Bamboo decks don’t shrink or swell due to temperature and humidity changes. They last longer, compared to decks made with most US hardwoods. 
• End-of-life of bamboo wood: Outdoor bamboo decks are often made with solid long lengths of bamboo glued together under high pressure. Because of the use of (synthetic) glues, these decks are not fully biodegradable. However, they can be partly recycled or up-cycle for other household projects. 

Bamboo decking is sustainable because this material has comparable properties to hardwoods without the disadvantages of slow growth cycles. These grass species reach maturity within a few years. They can regrow after being cut down without needing fertilizer, pesticide, and herbicide. 

Also, bamboo “wood” is lightweight. Transporting vehicles can carry more bamboo panels, reducing the carbon footprint of a unit. 

Tropical Hardwoods for Decking: A Few Words on Their Sustainability

Some tropical hardwoods are long-lasting (and stunning-looking) decking materials thanks to their natural resistance to rot, decay, and insect attacks. For example, old-growth teak decking is expected to last around 25 years, as long as redwood and longer than all other (untreated) US softwoods. Some much-loved tropical hardwoods for decking include:

• Mahogany 
• Ipe 
• Cumaru 
• Tigerwood 
• Teak 
• Meranti 

Though the durability of these hardwoods is a big contribution to their overall sustainability as a decking material, there are two other deciding factors: 

• Eco costs of logging 
• Transportation distances  

However, it is possible to source tropical hardwoods that are sustainably harvested. There are certificates such as FSC and PECC, which guarantee sustainable forestry management. In that case, the eco costs of such hardwoods can be lower than woods that might require treatment to stay a similarly long time outdoors. 

Providing that you can find FSC-certified tropical hardwoods, the distances and the mode of transport still affect the total carbon emissions. 

• The transporting footprint of these hardwoods is undoubtedly higher than woods sourced locally in the US. 
• However, the transporting emissions are not the same for all decking materials from the tropic. 
• For example, cumaru from Northern Brazil would have traveled much shorter distances to the US than Southeast Asian teak. 

In brief, tropical hardwoods are not as environmentally friendly as untreated softwoods available locally within the US. 

However, suppose you want naturally durable, beautiful tropical hardwoods for your deck. In that case, you should search for the most sustainable options in this group:

1. You should watch out that they have a sustainable certificate, such as FSC or PECC. You need to avoid timber associated with deforestation in tropical rainforests – the world’s most biodiverse places.
2. Traveling distance matters. For example, teak timber can come from as far as SouthEast Asia, but it doesn’t have to be. There are teak plantations in Brazil, which is much closer to the US. You should weigh all your options and go for the woods that travel the least.
3. It would also be an environmentally friendly option if you can find salvaged or recycled tropical hardwoods. 

Engineered Wood for Decking: A Few Words on Their Sustainability 

Wood plastic composite panels have become a popular choice for decking because of their low maintenance and wood-alike look. Besides, some of these engineered wood panels can last a couple of decades, as long as the most durable untreated decking woods out there (thinking redwood or teak). 

However, several studies show that composite panels often have much higher environmental impacts, including Global Warming Impact, than natural woods (both untreated and treated). The main reasons are the much higher manufacturing carbon emissions and the fact they are not recyclable. 

Yet, some engineered panels are more environmentally friendly than others. If you decide to go on this path, make sure your decking material has the highest recycled plastic content and that resins used are safe for the environment and, if possible, biodegradable. 

How Can You Buy More Sustainable Wood

The key to sustainably buying any wood is to check on relevant environmental and original certifications. Reliable certifications for sustainable woods are: 

• Forest Stewardship Council: 

An FSC certification ensures that the ash wood comes from responsibly managed forests that provide environmental, social, and economic benefits.

• Program for Endorsement of Forest Certification: 

PEFC’s approaches to sustainable forest management are in line with protecting the forests globally and locally and making the certificate work for everyone. Getting a PEFC certification is strict enough to ensure the sustainable management of a forest is socially just, ecologically sound, and economically viable but attainable not only by big but small forest owners. 

Why Is It Important to Buy More Sustainable Wood

Improperly managed logging (including illegal activities) can cause many problems for forest equality and diversity. One example is when loggers only cut down the biggest and tallest trees. That pattern would cause a reduction in the genetic diversity and quality of the trees within the stand, leading to gradual degradation of tree quality. 

In total, logging of forestry products from plantations accounts for 26% of forest loss, which is a combination of deforestation and forest degradation. However, the loss in bio-diverse forests in tropical climates is more significant (and sometimes less properly recorded) than in temperate, well-managed logging forests. 

Buying sustainable wood also means helping to prevent illegal or unsustainable logging, which harms the forests’ biosystems and accelerates climate change. 

Logging of forestry products from plantations accounts for 26% of forest loss. Cutting down trees for wood has a lesser impact on carbon storage than digging up the whole forest floor and turning it into farms or mines. However, if logging is not sustainably managed, it can badly damage wildlife.

When logging happens in tropical forests – the bio hotspots of our planet – the biodiversity loss can be much more damaging. Subtropical and tropical forests are packed with unique wildlife – endemic mammals, birds, and amphibians. The displacement of such wildlife during poorly managed logging would be a major contributor to global biodiversity loss. 

Sustainable management of forests also means that trees are cut down for timber only when they are mature. These trees will then be able to regrow and eventually replace the loss of canopy, absorb carbon from the atmosphere and reduce the effect of climate change.

Final Thoughts

You can build sustainable outdoor decking made with woods as long as the material comes from sustainably managed forests. These six types of wood – redwood, western red cedar, Nootka cypress, pine, douglas fir, and bamboo – are among the most sustainable options. It is thanks to the relatively low carbon emissions during harvesting, manufacturing, and transporting. You can make it even more sustainable by using decks made with these woods for as long as possible. Then, look into upcycling the material to extend its usage and/or arrange for it to be recycled fully.

Stay impactful,

Sources

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