Treating railroad ties for landscaping or garden use comes down to two things: sealing the creosote already in the wood so it doesn’t leach into your soil, and protecting the ties from further decay so they last as long as possible. Most used railroad ties were pressure-treated with coal tar creosote at the factory, which means they already contain a powerful preservative. Your job is to manage that chemical while extending the wood’s life in its new setting.
What’s Already Inside the Wood
Railroad ties are pressure-treated with coal tar creosote, a thick, oily substance made up of roughly 85% polycyclic aromatic hydrocarbons, 10% phenolics, and 5% other compounds. This cocktail is what gives ties their distinctive dark color and strong smell. It’s also what makes them last 30 years or more in direct ground contact, far longer than untreated wood.
Even after years of railroad service, a used tie still contains significant amounts of creosote. The chemical doesn’t fully break down or evaporate over time, which is both the advantage (durability) and the challenge (toxicity) when repurposing ties for home projects.
Protect Yourself Before Handling Ties
Creosote is not something to handle casually. Direct skin contact causes rashes, chemical burns, and increased sensitivity to sunlight. Breathing in the vapors irritates the respiratory tract, and long-term exposure has been linked to elevated cancer risk in the skin, lungs, kidneys, bladder, and other organs. The CDC’s Agency for Toxic Substances and Disease Registry lists it as a probable human carcinogen.
Every time you cut, move, or work on railroad ties, wear chemical-resistant gloves (not standard gardening gloves), long sleeves, long pants, and industrial-grade boots with chemical-resistant soles. Disposable coveralls are ideal since you can toss them afterward rather than contaminating your washing machine. If you’re cutting ties with a saw, add safety goggles and a respirator rated for organic vapors. Work outdoors in a well-ventilated area, and never burn scraps of treated wood.
Sealing Creosote-Treated Ties
The most important treatment you can apply to a railroad tie is a sealant that locks creosote inside the wood. This reduces chemical leaching into surrounding soil and minimizes the oily residue that bleeds out on warm days. The USDA Forest Service identifies three effective options for sealing creosote-treated wood: urethane (polyurethane), epoxy, and shellac. Coal tar pitch and coal tar pitch emulsion also work but are primarily used for flooring applications rather than outdoor landscaping.
For most home projects, an exterior-grade polyurethane is the practical choice. It’s widely available at hardware stores, relatively easy to apply with a brush or roller, and holds up well against weather. Here’s how to do it:
- Clean the surface. Brush off loose dirt, debris, and any flaking material. Let the tie dry completely. Creosote-treated wood can feel oily, so don’t expect it to look pristine.
- Apply the first coat. Use a disposable brush to work exterior polyurethane into the wood grain. Cover all exposed surfaces, paying extra attention to cut ends where creosote leaches most readily.
- Let it cure fully. Follow the product’s drying time, typically 24 hours between coats for exterior polyurethane.
- Apply a second coat. Two coats minimum. Three coats on any surface that will contact soil or be near garden beds.
Epoxy coatings create a thicker, more impervious barrier than polyurethane. They’re a better choice if the tie will sit against a foundation, line a vegetable garden, or contact areas where you want zero chemical migration. Epoxy is more expensive and less forgiving to apply, but it forms a hard shell that virtually eliminates leaching.
Extending the Life of Older Ties
Used railroad ties that have been out of service for a decade or more may show signs of surface decay, cracking, or softening at the ends. The original creosote treatment protected them from rot and insects, but that protection weakens as the chemical slowly migrates out of the wood over the years.
For ties showing early deterioration, you can apply a brush-on wood preservative containing copper naphthenate. This is one of the few preservatives available to consumers that’s effective in ground-contact applications. It’s typically sold as a 6% or 8% copper concentrate that you dilute with a petroleum-based solvent to a working strength of 0.5% to 2%. Brush or spray it generously onto any exposed, unsealed wood surfaces, especially end grain and cracks where moisture enters. The greenish color fades over time, and you can seal over it with polyurethane once it dries.
Proper drainage matters as much as chemical treatment. Ties sitting in pooled water will decay from the bottom regardless of what preservative they contain. Set them on a 2- to 3-inch bed of crushed gravel to promote drainage, and grade the surrounding soil so water flows away from the ties rather than collecting against them.
What Not to Do
Painting directly over creosote-treated wood with standard latex or acrylic paint doesn’t work. The oils in creosote bleed through conventional paint within weeks, leaving brown stains and a sticky surface. Only sealants specifically rated for oil-resistant applications (polyurethane, epoxy, shellac) can contain the bleed-through.
Avoid planting edible crops directly against unsealed railroad ties. Even sealed ties should have a barrier of heavy plastic sheeting between the wood and any soil used for food production. Creosote compounds can migrate into soil and be taken up by plant roots. For purely decorative landscaping or retaining walls away from garden beds, sealed ties are generally considered acceptable.
Never sand or power-wash creosote-treated ties. Both methods release concentrated chemical dust or spray that’s far more hazardous than handling the intact wood surface.
When Alternatives Make More Sense
If you’re building raised beds for vegetables, lining a play area, or working close to a well or water source, railroad ties are the wrong material regardless of treatment. The effort and safety precautions required to make them safe in those settings aren’t worth it when naturally rot-resistant woods exist.
Western red cedar heartwood, redwood, white oak, and Douglas-fir all last 20 years or more in above-ground use without any chemical treatment, based on USDA Forest Products Laboratory testing. For ground contact, pressure-treated lumber rated for that purpose (look for a “Ground Contact” or “UC4” stamp) is a safer, more predictable option than repurposed railroad ties. Black locust is another exceptionally durable species that resists rot naturally and works well for retaining walls and landscape timbers.
Railroad ties still make sense for applications where their weight, rugged appearance, and low cost matter more than food safety concerns: driveway borders, decorative retaining walls, steps on slopes, and erosion barriers. In those settings, a good sealing job and proper drainage will keep them functional for another 15 to 20 years beyond their railroad service life.