When people are considering building an outdoor wood bridge, the choice of wood is often paramount as the single most important decision of the entire process. The wood used will influence not only the design of the bridge, but also its aesthetic value and its reliability and durability over time. Luckily, the choice is easier than one would imagine, as ipe wood is the clear choice when it comes to bridge building material. Why is this?
Ipe is a South American wood, most commonly harvested from the forests of Brazil. Ipe is hard, tough, resilient, strong, and resists weather wear, abrasion, and naturally occurring wood rot. Ipe is incredibly dense and hard. Because of this, it is also naturally resistant to fire and mold damage. In fact, ipe is so resilient that its fire rating is equivalent to that of concrete. Compare this to a more common cedar or walnut deck that, in the case of fire, will act as kindling. An ipe bridge will just about last forever.
Ipe is also beautiful. In its appearance, it is similar to mahogany. It makes a fine interior wood when it is shined and varnished. It has that dark, blood red brown that is so desirable in finished woods. You’re guaranteed to love the look of an ipe deck.
With this in mind, let’s look at ipe versus some common bridge woods.
Mahogany. Although mahogany is usually a good choice for high quality bridge material, there are some significant disadvantages compared to ipe. Firstly, mahogany wood has to be treated and re-sealed every few years, and every year if you want to maintain the wood for any length of time. Ipe does not need to be sealed at all except for on the ends of the lumber and will, even if left un-treated over the life of the bridge, will out last mahogany. If you treat and seal ipe deck wood, then it will last nearly forever. Additionally, since mahogany is used as an interior wood and in the production of consumer materials like guitars, the supply has been dwindling. Because of the diminishing supply, it is very possible to get lower grade and inferior mahogany. Twenty years ago, this was not a problem, but today, a lot of the mahogany on the market is of an inferior quality.
Cedar and pine. Unfortunately, most bridges are constructed out of either cedar or treated pine. Both of these woods are susceptible to rot, particularly in wet climates or in climates that experience extremes in temperature. Pine is also a fire hazard.
Ipe is rated higher than cedar and pine in durability and resiliency, and also rated much higher in terms of appearance. If you are interested in building the best bridge possible, you should choose ipe.