People say it all the time. I know, I know. How can you build a deck of mahogany? It’s so expensive. Your grandmother had that gorgeous mahogany dining table, and it cost $300 over 60 years ago. But that table was made of furniture grade mahogany (Swietenia mahogany or perhaps swietenia macrophylla) — dark, fine-grained hardwood from Honduras. Don't worry it's not the same thing.
Meranti mahogany deck
There are many, many species of wood called “mahogany.” The mahogany used for deck flooring is not Honduran mahogany. It is normally Cambara from Brazil, or Meranti from Indonesia. And the cost? Decking mahogany costs more than Pressure Treated pine (“PT”) and more than knotty inland cedar – but less than D cedar, A cedar, redwood, ipe, and garapa. Indeed, it costs less than any other outdoor wood and less than any artificial composite or plastic decking. Whatever you choose for the floor and rails of your deck, the frame is always pressure treated pine.
People like mahogany decking for its hardness, rich color, tight grain, and knot-free appearance. It naturally resists rot and does not splinter, especially if treated with a good penetrating oil. It is best fastened with high quality stainless steel, since the resins that protect mahogany from rot can interact with lower grade stainless steel to create blackish stains. Decking mahogany is a true exterior hardwood that stands up well to foot traffic and will endure outside for many, many years.
Of the two types of decking mahogany, Cambara is more consistent in color and lacks the dark and light boards common with Meranti mahogany. Other than that, the two are very similar — in features and in price.
Overall, people choose mahogany for its appearance and value: rich, dark color and hardwood durability — but at a moderate price. It is commonly available in two sizes; 1×4 is strong enough to span joists 16″ on center. The premium you pay for the wider 5/4 x6 is somewhat extravagant because the extra thickness is not needed.