The Best Wood for Boat Trailer Bunks
Any avid boater is going to need to have a reliable trailer with which to transport the boat. Whether you have a little fishing boat or a personal watercraft, a good trailer can make transportation a lot easier. And that means proper trailer maintenance.
Boat trailer bunks are there to help support and cushion your trailer as it is in transition or storage. They need to be tough but gentle, they should be long lasting and not susceptible to wear and bumps and rot. While you should have some reliable boat trailer bunk carpeting on the outside, the wood inside is just as important. Not all kinds of wood are up to this task and some are definitely better than others. Let’s take a look at the best wood for boat trailer bunks.
The Best Wood for Boat Trailer Bunks
You have plenty of choices for wood in a boat trailer bunk. Some are much more popular than others, and some are much cheaper than others. You’ll have to decide which features are most important for you.
I recommend pressure treated pine for most casual boats. It’s the go to wood for boat trailer bunks. It’s cheap and lightweight and it works. It’s not fancy, by any means, and other woods will be sturdier, better looking or longer lasting. But when you balance everything out, pressure treated pine ticks a lot of the boxes you’re looking for without costing too much. It’s tough enough, it’s water resistant, it’s cheap, it’s light, and it’s easy to find.
Better Wood Options
Pressure treated pine is a good standard option. While I think it’s the best all around option for most people who need bunks in a hurry and don’t want to waste much time on them, it’s not the “best” wood overall.
This is probably the best option for wood that you can get, but it is a little pricier than pressure treated. Cypress is incredibly durable and it looks nice as well. You don’t need to paint it though some choose to. I don’t think there’s a big benefit to it beyond maybe trying to make everything match if you have a color scheme going. That said, you’re likely going to need to keep touching it up, so it doesn’t make a lot of sense.
One thing to remember about cypress is that, despite its overall high quality, saltwater is a lot worse for it than fresh water. Keep that in mind when you look into maintenance for cypress bunks. They’ll need some extra care if your boat is in the ocean.
Oak is another great option for boat trailer bunks. It’s a very resilient, durable wood so you can count on it to have a long life. White oak in particular is extremely resistant to rot and looks very nice when you have them installed. Your biggest concern here is that it’s heavy but given how much wood you need for reliable bunks, it shouldn’t be that big of a deal. For a larger trailer and larger boats it may come into play, however. Just remember the weight when you’re calculating what your axles can handle.
Oak is not pressure treated nor does it need to be. That said, it would be a good idea to seal your oak just to ensure its long life. If you seal it once every year or two it may last up to 25 years or more.
Douglas Fir is a softer wood but it’s also very resistant to rot, which is something you want. Green Douglas Fir is often an even better option. It offers good stability and long life overall. Don’t go for the kiln dried stuff, however, as it’s more prone to breakage.
This is a real mixed bag here. Some composite woods are amazing and last for ages. Some are outright garbage. How do you know which is which? Well, that can be hard to figure out because who knows what composite you might be looking at. One thing you can keep in mind is that there is no such thing as maintenance free wood in an aquatic application. If someone is trying to sell you wood for boat trailer bunks and they say it’s maintenance free, you may want to walk away. It just can’t be true. No matter how good it is, at some point, that wood will need to be maintained or it will fall apart.
Some older composites from back in the day were marketed for things like boat docks as maintenance free and there were actually class action lawsuits filed as a result of the sheer number of them that rotted away and caused serious damage.
That said, you can find quality composite woods that can stand up fairly well to water and these kinds of tasks. Look for composites that come with a clear warranty. Something like a teflon infused composite offers economic benefits over other hardwoods and popular alternatives when it comes to wood for trailer bunks.
There are a handful of lesser known woods that are actually amazing for any water-related jobs like patio decking. You’re going to pay for these woods because they tend to come from South America but they are incredible when it comes to handling water and stress. Woods like Ipe, Tigerwood, Brazilian Teak, Massaranduba and others. Believe it or not, some of these woods can last 40 to 50 years or even longer. Some are reputed to last 75 years under fairly stressful conditions.
These woods look great but aren’t cheap. Honestly, these are so nice it’s almost a waste to use them as boat trailer bunks. These are great for decks and furniture and stuff you want to look at all the time. But if you’re committed to having an extremely well made boat trailer that does look amazing and perform well, these are good options.
Woods to Avoid
A lot of lumber out there is great for furniture and decorative touches but are less ideal for a boat trailer bunk. You may see cedar and redwood as suggestions because these are both tough and durable woods. I can’t recommend them for trailer bunks, however, because of the job a trailer bunk does. These are a little more likely to suffer breaks than other kinds of wood, they just don’t have that give that you want. Remember, you have the weight of a boat, the stress of traveling down the highway, the effect of water and sun and age all working against you. Not every kind of wood can stand up to that abuse.
Should You Use Pressure Treated Wood?
Arguably the most popular wood for boat trailer bunks is pressure treated pine. It combines most of the qualities you want in one place. It’s lightweight but still very durable. It’s also forgiving, in that it has some elasticity to it. It’s not so rigid that it will break or cause damage like some harder woods might.
As the name suggests, this has received a pressure treatment. Under high pressure, water and preserving agents are forced deep into the grain of the wood. Depending on the type of wood you can expect that it will have been treated with things like alkaline copper quaternary (ACQ), copper azole (CA) or micronized copper azole (MCA). These stop the natural rotting process of wood and also help it resist things like fungus and even termites. Perhaps most importantly when it comes to boat trailer bunks, they help resist moisture. All of that means the wood can have a longer lifespan than normal.
One thing to remember about pressure treated wood is that the copper can react with the metal of your trailer. Stainless steel should be okay, but you may find problems with aluminum. Also, the pressure treated wood may react in salt water and release chemicals. Check with the manufacturer to see if it can work as a trailer bunk before committing.
Another thing to keep in mind is maintenance. Pressure treated pine needs to be sealed annually to keep it performing the way you want it. If you don’t reseal it the benefits of using pressure treated wood will soon fade and you may find your wood cracking or warping.
Dangers of Choosing the Wrong Wood
So what happens if you use just any old wood? Maybe nothing at all, you could get lucky. But there’s a good chance the wrong wood can lead to some catastrophe for your boat.
Some woods can become remarkably slimy as they age and rot. Most bunks are covered in carpeting but you don’t necessarily need that, especially on nicer woods like cypress. Sometimes slip-resistant strips are all you need so you can still enjoy the look of the wood itself. Plus, even carpet gets slippery if it’s cheap.
Poor quality wood can develop fungus as it begins to rot. If it’s dry that makes the wood brittle and crumbly sometimes but if it maintains a certain level of moisture it can almost form a slick on the wood. That can make it dangerous for your boat as you load and unload it.
This is your main concern when it comes to poor wood choice. It’s potentially the result of several things going wrong at the same time. A wood that isn’t strong enough may crack from the stress. At the same time, a wood can be strong but somewhat brittle, kind of like iron. The entire weight of the boat, the friction of motion, can put too much stress on certain points and cause breakage. And, of course, if it’s wood that is ill-equipped to handle moisture then you have a problem as well. If the wood is not rot-resistant then, over time, all the water it absorbs can lead to natural decay and fungus growth. It may also fall victim to burrowing insects. All of that adds up to cracks and breaks that could be catastrophic.
Warped bunks are a real hassle. The reason you need to pressure treat your pine and seal other kinds of wood is because of the cell structure. Water can get inside the wood in the spaces between cells and essentially force those cells aside over time, making the wood warp and change shape. That means perfectly straight planks becoming bumpy and uneven. At that point, your boat cannot be reliably supported by them. Likewise, the bolts holding the wood to the frame of the trailer may loosen. So you could end up with a trailer that is wobbly and at risk of falling, getting scratched or worse, or the bunks themselves could fall off.
Aren’t Boat Trailer Bunks Slippery All the Time?
This is arguably one of the biggest issues for trailer bunks that aren’t high quality. Bad wood and bad carpeting along with poor cleaning habits can cause a real slimy build up. The wrong materials can make those bunks slippery even when they’re not that wet and unclean as well. That’s why making the right choice and proper upkeep is important.
Many of the woods I’ve recommended do an amazing job of resistant water and fungus. That keeps them smooth and dry for quite a long time. Eventually every kind of wood breaks down but as long as you keep it clean and seal it as necessary, a good quality bunk will stay straight, dry and reliable for years.
Wood alone does not a bunker make. You need to consider a few other things before you can call it a day on the type of wood you want for your boat bunker.
You do have an option for picking up bunks that aren’t even made of wood these days as well. Aluminum bunks are fairly popular and there are some synthetic bunks you can buy as well. These can be more expensive and are potentially subject to the same environmental concerns, though aluminum is very sturdy and durable. The potential for scratching the boat is there if they’re not covered by some material to act as a buffer.
Maybe nine times out of ten a wooden boat trailer bunker is carpeted. You have a lot of choices to go for when it comes to bunk carpet and we’ve covered that elsewhere so have a look if you’re interested. Not all boat trailer bunks need to have carpeting though and we’ve mentioned that already. If you’re going to invest in a really exotic wood like ipe, it’d be a real shame just to wrap it in some marine grade carpet carpet and hide it away. Likewise with cypress or oak. It kinds of defeats the purpose.
There are vinyl panels you can install to help buffer your bunk board and prevent slipping if you use a higher quality wide. They allow you to still enjoy the look of the bunk boards but provide extra security and stability for your boat.
Carpeting is a good idea for woods like pressure treated pine or Douglas fir. Basically any wood that is going to splinter or isn’t there for pure esthetic reasons. Carpeted bunks provide more security, durability and support for your boat. Just make sure you follow directions for properly attaching the carpeting to the wood and you should be okay.
Carpet material can vary so you need to shop wisely. Plain outdoor carpet will do in a pinch but it’s not always the best.
This should go without saying but you need to be aware of what you’re using to secure your trailer bunks to boat trailers themselves. Especially if you boats spend time in saltwater. You don’t want hardware that is going to corrode right away in salt water because that can ruin your bunks and your boat pretty quickly. If you have stainless steel hardware included in a bunk kit, that’s a good start. Galvanized bolts are always a good idea, or anything else designed to stand up to the abuse of saltwater without rusting away on your.
With carpeting, make sure you use stainless staples.
Saltwater vs Freshwater
We mentioned the types of fasteners and hardware to use and also concerns with pressure treatments. These things are often very dependent on whether you boat in freshwater or saltwater. Pressure treated wood may leak chemicals into the water if it’s submerged for extended periods and this is more likely in saltwater than freshwater. Check to see if the pressure treated wood you want to use is safe for this application. As boaters, we always want to be stewards of the environment. Polluted water isn’t fun for anyone to boat on so we have to be at the forefront of being responsible about this sort of thing.
We mentioned already that woods like oak and pine need regular sealing. Lots of good quality woods are low maintenance but that never means no maintenance. Make sure you seal your wood as needed to keep it safe from excessive moisture and, in turn, rot and fungus. It will also protect the wood from UV rays which can bleach or wear the wood out over time as well.
Stain aside, keep your boat trailer bunks clean. Your boat is likely not very pristine when it comes out of the water so when your trailer is unloaded, make sure you give them a cleaning after they’ve been used. Get off the layers of muck and mud that may have built up either from the bottom of your boat or just travel on the road. This will also help extend the life of those bunks for quite a while.
You should give your bunks a good inspection at the beginning and end of every season. Make sure the wood isn’t warping or cracking. Check to make sure the hardware holding them in place isn’t corroded and that the connections are secure. Check for signs of warping or cracking around them especially.
If anything needs to be replaced it’s best to get on it sooner rather than later. Small cracks can become big cracks a lot faster than you’d think. Likewise, warped wood puts your boat at risk every time you load it up for transport.
The Bottom Line
You can spend an awful lot of time and money on buying and installing new boat trailer bunks. You can also get it done pretty quickly at a more reasonable price. Cheaper woods can get the job done but may require more maintenance and will have a shorter lifespan overall. For that reason there are some real pros and cons to any number of different woods, as we’ve seen. Go with what looks best to you in terms of not just function but price and look. Keep up with maintenance and your bunks should last you for many years to come.