If you've got your heart set on building a wood jetty, then you need to source timber that can cope with being close to and in contact with water on a regular basis. It also needs to be able to handle other issues, like the weather and pests.
When you ask your neighbours about the woods they used to build their jetties, a fair few tell you to use jarrah. Why is jarrah good for jetties?
Resistant to the Elements
As a hardwood, jarrah has a few natural resistance benefits. Its strength and durability make the wood better able to cope with water and weather extremes. So, if you use jarrah for your jetty's piles, then the wood should be strong enough to hold fast without significant damage in high winds.
Plus, jarrah doesn't decay as easily as other woods. Some woods start to rot quickly when they are in or close to water; jarrah is less likely to have this problem.
Its dense structure also makes jarrah more fire resistant. While you may not think that this matters much for a jetty that sits on water, it's still a useful feature. Fire can damage parts of your jetty that aren't in the water quite easily, so it's a good idea to use a fire-resistant wood.
Resistant to Bugs
Like any wood, the wood you use to build your jetty should be as bug resistant as you can make it. Don't assume that your jetty's proximity to water will protect it from landlubber insects like termites. They can access your jetty from the land side and cause a lot of damage.
Plus, wood in or close to water also sometimes attracts marine bugs, like borers. Like termites, these creatures damage wood quickly by attacking it and weakening it. Their attack comes from the water, however. So, your jetty could have insect problems from both sides.
Once of the reasons that jarrah is often used for marine building is that it has a natural resistance to bugs. It is less likely to be damaged by termites than some other woods and it also handles marine borers better. This gives you a better chance of keeping your jetty intact for the long-term.
While jarrah is often used for marine constructions projects like jetties, there may be other materials out there that are also suitable. To find out which materials you can use safely, ask your jetty construction company for advice.