Choosing the right lumber when planning a DIY ramp is essential in ensuring that it stays safe and stands the test of time. You can’t just use any off-the-shelf pine and expect a coat of paint to protect it. Pressure-treated (PT) lumber is the answer to soaking rains, baking sun, and soil-borne organisms.
A lot of people think pressure-treated wood is just dipped in a vat of chemicals. To make this stuff, raw timber is rolled into a massive pressurized tank called a retort. First, the machine sucks all the air out of the wood cells to create a vacuum. Then, it floods the chamber with a chemical mix - usually copper-based - and cranks up the pressure.
This force-feeds the preservative deep into the grain. The copper acts as a fungicide and a pesticide. It makes the wood fibers toxic to the fungi that cause rot and the termites that want to hollow out your ramp’s support posts.
Selecting the Right Species
The type of wood you get usually depends on where you live, and it matters for the strength of your ramp.
In the South and East, you are almost always getting Southern Yellow Pine. It is the best wood for treatment because it is porous enough to soak up the chemicals but dense enough to hold a massive amount of weight. If you are building a ramp for heavy equipment or a vehicle, this is what you want.
Out West, you will likely see Douglas Fir or Hem-Fir. These are refractory woods, meaning they resist liquid. To get the chemicals inside, the mill has to run the boards through a machine that punches thousands of tiny slits into the surface. This is called incising. It looks a bit like the wood was run over by a tiny tank, but those slits are what keep the board from rotting from the inside out.
Use Categories: Don't Buy the Wrong Stuff
For the walking surface and handrails of your ramp, UC3B (Above Ground) is fine. It gets wet, but it also dries out in the wind. But for the posts that sit on the ground or the joists that hold the ramp up, you must use UC4A (Ground Contact). If you use Above Ground wood for your footings, the ramp will be structurally compromised within a few seasons because the moisture in the soil never lets the wood dry out, eventually overwhelming the lower chemical concentration.
The Boat Ramp Challenge
Building a boat ramp is completely different to a backyard walkway. Standard pressure-treated wood from a big-box store will fail prematurely if it is constantly submerged or splashed with brine.
For boat ramps, you need Marine Grade lumber. In many areas, this means looking for wood treated with CCA (Chromated Copper Arsenate). While CCA was phased out for residential use like decks and playsets years ago, it is still the gold standard for marine environments because it sticks to the wood fibers better than anything else when submerged.
Hardware is the other half of the boat ramp equation. The copper in treated wood eats through regular steel. For a boat ramp, you cannot use standard zinc-plated screws, which will rust and snap, and your ramp will float away while the wood is still perfectly fine.
Tips for the Build
As that wood dries, it is going to shrink. If you are laying down the ramp surface, gap the boards tightly. By next summer, you will have a perfect quarter-inch gap between them.
Slather it on every end-cut before you bolt the pieces together. It seals the wound and prevents rot from starting at the joints.
Safety and Longevity
Wear a mask when you're cutting - copper dust isn't something you want in your lungs. Never burn the scraps. The smoke is toxic, and the ash contains concentrated chemicals.
If you want your ramp to stay looking good, wait about two months for the wood to dry out. You can then use a high-quality oil-based sealer which stops rot. But it doesn't stop the sun from cracking the wood. A good sealer keeps the water out and the ramp looking solid for decades.