Few decisions carry more weight in exterior woodwork than the choice of timber. Get it right and you have furniture or joinery that weathers decades with quiet dignity. Get it wrong and you are watching a beautifully crafted piece split, grey unevenly, or shed its finish within a season.

Two species sit at the top of every serious maker's shortlist for outdoor work: teak and iroko. Both are tropical hardwoods with formidable natural durability ratings. Both are used by professional furniture makers, boat builders, and architects the world over. And yet they are meaningfully different in cost, workability, grain behaviour, and long-term performance.

Understanding those differences is the only way to choose correctly — not just for this project, but for every outdoor build that follows.

Why Teak Has Earned Its Reputation

The characteristic golden heartwood and tight grain of well-oiled plantation teak.

Teak (Tectona grandis) is the benchmark against which every other exterior hardwood is measured. That status is not marketing; it is chemistry.

Natural Oils and Silica Content

Teak's heartwood contains unusually high concentrations of natural oils and a waxy resin that actively repel moisture. These are not surface treatments — they are synthesised by the tree itself and remain chemically active in milled timber for decades without any human intervention.

The practical result is a wood that sheds water rather than absorbing it, resists the swelling and shrinking cycle that destroys less stable species, and maintains dimensional integrity under conditions that would distress almost any other commercial hardwood.

Teak also contains silica deposits within its cell walls — the same mineral compound found in sand and glass. Silica is highly abrasive and is the principal reason teak dulls cutting edges faster than any temperate hardwood. This is not a surface phenomenon; the silica is distributed through the wood's cellular structure, meaning every pass of a blade or plane iron is working against it. We will return to this at the bench.

Durability Class and Longevity

Under the European EN 350 grading system, teak is classified as Durability Class 1 — the highest category, indicating an expected service life of 25 years or more in ground contact, and significantly longer above ground, without any preservative treatment. Almost no commercially available temperate hardwood comes close.

Untreated teak left outdoors silvers gracefully to a warm platinum-grey — a process driven by UV degradation of surface lignin rather than structural deterioration. Oiled regularly with a quality teak or hardwax oil, it retains its rich golden-brown for many years. Either way, the underlying wood remains structurally sound.

Sustainability and Sourcing

This is where the conversation becomes more nuanced. Old-growth teak from Myanmar and mainland Southeast Asia — historically the source of the most prized stock — is now heavily restricted, and much of what enters unregulated supply chains carries serious ethical risk.

The responsible choice is plantation teak, most commonly grown in Indonesia, Costa Rica, or Central America. Plantation-grown trees are harvested at 20–40 years rather than the century-plus cycles of old-growth forest, which limits the time available to develop the same oil density. The timber performs well and is structurally sound, but it lacks the extreme oil saturation of old-growth heartwood. FSC-certified plantation teak is the only option a conscientious maker should specify.

Expect to pay accordingly. On a price-per-board-foot basis, quality teak is among the most expensive commercial hardwoods available globally — a premium that reflects both scarcity and performance.

Iroko: The Compelling African Alternative

Iroko's interlocked grain is visible across the face of a freshly planed board.

Iroko (Milicia excelsa, formerly Chlorophora excelsa) is the timber the trade has long called "African teak." The nickname is earned, not merely borrowed.

Iroko's Properties That Matter Outdoors

Iroko shares a great deal structurally with teak. It is a large-pored, open-grained tropical hardwood rated at Durability Class 2 — meaning it outperforms almost every temperate hardwood in exterior applications, though it falls one step below teak's Class 1 designation.

Its natural oil content is lower than teak's but still meaningful. More importantly, iroko's density and interlocked grain create a timber that resists face splitting even under repeated wetting and drying cycles. This is a meaningful practical advantage in outdoor furniture: pieces that cycle through rain and sun place enormous stress on the wood's surface layers, and iroko's grain structure dissipates that stress rather than concentrating it into cracks.

The heartwood colour ranges from a medium yellow-brown when freshly milled to a warm, rich brown with age. It patinas attractively outdoors and responds well to both oil and film finishes.

Price-to-Performance Ratio

Here is the honest case for iroko: it delivers between 80% and 90% of teak's outdoor performance at roughly 40%–60% of the cost, depending on market and grade.

For large-scale exterior commissions — garden furniture sets, decking, pergola structures, external joinery — that gap is commercially significant. Many professional furniture makers specify iroko not as a budget compromise but as an intelligent primary material choice, particularly where the scale of the project makes teak's premium prohibitive without proportional benefit to the client.

Sustainability Profile

Iroko is sourced primarily from West and Central Africa. As with teak, chain-of-custody certification matters — look for FSC-certified stock and be sceptical of suppliers who cannot provide documentation. Iroko grows more prolifically than teak and reaches commercial grade faster, making FSC-certified West African iroko a generally more sustainable commercial option than non-certified plantation teak from regions with weaker oversight.

Workability at the Bench

Reading grain direction carefully before each pass is essential when planing interlocked iroko.

Both species will challenge you. Anyone who suggests tropical hardwoods are straightforward to mill has not spent serious time at the bench with them.

Teak at the Bench

The silica in teak's cell structure is not merely abrasive — it is destructive to unprepared tooling. Carbide router bits and saw blades will dull faster than on any temperate hardwood, and high-speed steel edges will degrade even more rapidly. For machine work, carbide-tipped tooling is non-negotiable, and increased feed rate maintenance is essential.

At the hand tool bench, teak rewards sharp, well-set irons. A freshly honed chisel or a properly tensioned plane will cut cleanly — teak's grain is generally straight to slightly interlocked, and with a prepared blade it parts well. The problem is dull tools: teak's silica and natural oils cause blunt edges to burnish and compress the surface fibres rather than sever them. That burnished layer resists finish penetration, and no amount of sanding will fully correct it if the cellular structure has been compromised. Sharpness is not optional with teak; it is the fundamental prerequisite for a quality result.

Iroko at the Bench

Iroko's interlocked grain is its most significant workability challenge. The grain reverses direction along the length of a board — sometimes subtly, sometimes dramatically — which means a hand plane set correctly for one section will tear out the next if you carry the same approach.

This is not a reason to avoid the species. It is a reason to read the grain carefully before each pass, adjust iron projection conservatively, and make heavy use of a cabinet scraper for final surfacing. Iroko responds exceptionally well to a sharp scraper and will yield a glassy surface without the tearout risk that troubled your plane. A card scraper is not a finishing shortcut here — it is the correct tool for the job.

Both species contain extractives that can inhibit adhesive cure and prevent oil-based finishes from penetrating cleanly. Standard practice applies to both: sand to your final grit, blow or brush clean, and allow freshly cut or planed surfaces to off-gas for at least 24 hours before applying any finish. Skipping this step is the most common reason for adhesion failure with tropical hardwoods.

Climate Performance and Dimensional Stability

A UV-filtering oil finish is essential for preserving tropical hardwoods in high-exposure environments.

Dimensional stability under thermal and moisture stress is the final test for any outdoor timber — and the one most relevant to makers working in high-UV, high-heat environments.

Teak's superior oil content and low volumetric shrinkage coefficient give it a meaningful advantage in extreme climates — those defined by intense UV radiation, prolonged heat, and sharp transitions between air-conditioned interiors and outdoor ambient temperatures. Its resistance to the swelling-and-shrinking cycle means joinery and glue lines remain under less stress across seasons.

Iroko performs well but is more responsive to moisture cycling. This is not a disqualifying characteristic, but it does sharpen the requirements around preparation. In high-UV environments such as the GCC and wider Middle East, both species must be sourced from stock that has been rigorously kiln-dried to a stable equilibrium moisture content before fabrication. For outdoor furniture in this region, timber arriving at anything above 10–12% MC is a risk — checking, end-grain splitting, and joint failure are common consequences of building with under-dried stock regardless of the wood's inherent durability class.

For any outdoor piece destined for high-UV exposure, a UV-filtering oil or modified hardwax oil finish is essential on both species. UV degrades surface lignin, not the wood itself, but the resulting greying and surface checking — if left untreated — allows moisture ingress into areas where the wood's natural oils offer less protection. A UV-stable penetrating finish applied at installation and refreshed annually is the single most effective maintenance step for exterior tropical hardwood in this climate.

Teak vs Iroko: Summary Comparison

Frequently Asked Questions

Is iroko as good as teak for outdoor furniture? Iroko is not identical to teak, but it is a genuinely durable outdoor hardwood rated at Durability Class 2. For most furniture applications — garden seating, tables, loungers — it performs excellently and will last decades with proper finishing and periodic maintenance. The performance gap becomes more relevant in marine environments or ground-contact applications, where teak's Class 1 rating and higher oil saturation give it a clearer advantage.

Why does teak cost so much more than iroko? Teak's price reflects both scarcity and performance. Old-growth teak is heavily restricted, and certified plantation stock takes 20–40 years to reach harvestable size with meaningful oil density. Iroko grows more quickly, is available across a wider supply region, and reaches commercial grade faster — all of which keeps its cost more accessible without meaningfully compromising durability for most exterior applications.

What is the best wood for outdoor furniture in hot climates? Both teak and iroko are well-suited to hot climates, provided the timber has been properly kiln-dried before fabrication and finished with a UV-protective oil or hardwax oil. Teak's higher natural oil content gives it a slight edge in extreme UV environments, but iroko finished correctly will perform reliably in most warm-climate exterior settings. In either case, finish quality and maintenance frequency matter as much as species selection.

Does iroko need oiling outdoors? Yes. Like teak, iroko benefits significantly from regular oiling in exterior applications — typically once or twice per year depending on exposure and aspect. A quality hardwax oil or dedicated exterior oil will protect the surface, slow UV-driven greying, and maintain the wood's warmth. Left completely unfinished, iroko will silver over time; while visually acceptable to some, it increases surface checking risk in harsh conditions because the depleted surface layer is more susceptible to moisture ingress.

Can iroko be used for decking? Iroko is a capable decking timber. Its density, natural durability, and interlocked grain create a dimensionally stable, wear-resistant surface underfoot. Specify properly kiln-dried boards, pre-drill all fixing points to prevent splitting along the grain, and apply a penetrating exterior oil before installation and again after cutting boards to length. It is widely used in European decking projects and performs equally well in warmer climates with appropriate finish maintenance.

Make Confident Material Choices for Your Next Exterior Build

Whether you are designing an outdoor dining set, specifying joinery for an exterior commission, or deepening your understanding of the materials you work with — knowing your timbers is fundamental to making well.

Our free Wood Species Guide covers the hardwoods, softwoods, and tropical species that matter most to furniture makers and hobbyists, with practical notes on workability, finishing, and sourcing.