I’ve had quite a few readers ask me if railroad ties attract termites. Some people use railroad ties for landscaping or retaining walls that are often near their homes. Understandably, people don’t want to place large amounts of wood in their yards if they might attract termites, which is why I get this question.
On the other hand, other people assume railroad ties with enough creosote are termite-proof, but this isn’t the case. Railroad ties can attract termites, particularly if they’re older or if they’re not installed properly.
Creosote only penetrates about a half-inch into railroad ties. It doesn’t take much of a crack to expose the railroad tie enough to where termites or carpenter ants can get past the creosote. Also, the creosote leaches away over time.
Do railroad ties with creosote prevent termites from eating them?
Most railroad ties you might buy for landscaping or a retaining wall were originally soaked in creosote. People often assume that creosote protects railroad ties from termites and other wood-destroying organisms.
While creosote normally does a decent job at repelling termites and other insects from eating railroad ties, it doesn’t make them termite-proof. For example, in their laboratory evaluation of the effectiveness of different wood preservatives, E. W. B. Da Costa et al. (1973) found that creosote protects wood against (Australian) subterranean termites through a “by a deterrent and/or repellent mechanism, rather than by a termiticidal effect.” Do Costa et al. concluded from their study that creosote offers over 30 years of termite protection.
But, there are some important railroad tie installation steps people often skip that help prevent railroad ties insect infestations:
- Try to use newer railroad ties. The railroad ties people buy for retaining walls or landscaping are nearly always used to save money. If you’re installing railroad ties anywhere near your home, try to get ties that are in the best shape you find. You have no clue how old second-hand railroad ties are nor do you have any clue how much creosote remains in them. New railroad ties are normally treated last 30 years or more but eventually termites and carpenter ants damage them.
- Railroad ties should be installed over a gravel base. About a 4-inch gravel base acts as a barrier between the soil and your railroad ties (it’ll also make leveling the bottom tie easier). Direct soil-to-railroad-tie contact allows more moisture to seep into your railroad ties and for subterranean termites to find your railroad ties easier.
How to tell if railroad ties have creosote
First, if you see a black, oily, or tar-like substance on railroad ties’ surface, that’s the creosote. On hot days, creosote tends to seep out more than normal.
Next, if you know for certain that your railroad ties are new (or newish), then you can expect creosote to last around 30 years, assuming they are not excessively exposed to water and assuming that you don’t cut them.
Finally, creosote has a distinct smell to it. It smells a bit like asphalt. This is also more prevalent on hot days. If you see a black, sappy, tar-like substance on your railroad ties or smell something like asphalt, those ties likely have a good bit of creosote left protecting them. It’s tough to determine though because one part of a railroad tie might have sufficient creosote for protection while another portion does not. Termites or carpenter ants only need a small entryway into a railroad tie to start eating it from the inside (where there’s no creosote) and work their way outward (where the creosote layer is).
How to tell if my railroad ties have termites in them
It’s difficult to know if your railroad ties are being attacked because if termites get into your railroad ties, they’ll eat them from the inside out. So, to detect termite activity in or near your railroad ties, keep an eye out for the following evidence of termite activity:
- Termite mud tubes: Normally, subterranean termites can find their way from the soil straight into your railroad ties without building protective mud tubes because railroad ties usually lie in such a way where at least one surface touches the soil. Still, if you use spot termite mud tubes traversing up your railroad tie retaining wall, for example, your ties are probably being eaten by termites.
- Termite swarmers: If you notice flying termite swarmers emerging from or nearby your railroad ties, that means there’s a reproductively mature termite colony near your railroad ties. Chances are they were feeding on your railroad ties, so you’ll want to investigate further. You can do that with a tap test. If you need to learn how to identify flying termites, read this.
- Tap test with a screwdriver: Maybe once or twice a year, go along the length of your railroad ties and tap them with a screwdriver. If a railroad tie has been significantly hollowed out by termite damage, you’ll notice a difference in sound the tapping sound. In other words, a solid portion of a railroad tie will sound different than a hollowed-out section.
You might also notice a sudden increase in birds, lizards, toads, or frogs around your wood railroad ties. If you see this, try to notice if they’re eating something. It’s not unusual for termite swarmers emerging from railroad tie walls to attract termite predators looking for an easy meal.
Summary of termites and railroad ties
To conclude, termites can be attracted to railroad ties, particularly when their older and their creosote has leached out.
If you really want to use railroad ties for landscaping or a retaining wall, keep them as far away from buildings as feasible and inspect them once or twice a year for termite activity.
Additionally, when you install them, install them on a gravel layer around 4 inches thick and minimize cutting or splitting your ties because doing so penetrates the protective creosote layer.
Finally, understand that even brand-new railroad ties only have around a 30-year shelf life. After that, the creosote has leached out enough to where railroad ties have little protection against termites and other wood-destroying organisms.