6 Types of Lumber For Your Outdoor Wood Projects
Planning outdoor wood projects and not sure what wood to use? Find out how to pick the best lumber that lasts a long time, is easy to use and looks great.
There are many structures in the garden that use lumber of one type or another. Raised vegetable beds, compost bins, fences, pergolas, arbours, greenhouses, planters, decks and even chairs and tables.
Wood has usually been a go-to material for these types of structures as it is readily available, easy to work with the right tools and feels warm and inviting to the touch.
Since these structures are outside, exposed to the weather, they need to stand up to adverse elements and last. Otherwise, you will end up having to replace them on a regular basis and that gets to be very expensive!
So what is the best lumber to use to avoid having it rot into the ground? And since your goal is to create a tranquil garden, that is pleasing to your eyes, what lumber is visually appealing without much effort?
Note: Not a Do-It-Yourselfer (DIY)? This information is still valuable even if you are hiring someone to build the structures for you. It is always a good idea to be informed, so that you know when someone is telling the truth versus trying to cut corners.
Non-treated Pine, Spruce, Fir, etc.
These softwoods are usually the cheapest lumber you can buy at least in temperate regions where these evergreen trees grow. This is the main reason why it is the most common lumber that novice gardeners use, especially when on a tight budget.
Generally, these are not recommended for use in the garden if left exposed to sun, rain wind and cold temperatures. Especially if they are touching the ground. I originally had made my raised vegetable beds with untreated fir boards. They lasted only a few years before rotting into the ground.
If you do decide to use these softwoods, you need to protect them with a stain, paint or another preservative. And do not use them for ground contact. Always try to elevate them on bricks or stone to keep them from being in direct contact with standing water and wet dirt.
Aesthetically these can look nice if stained or painted. Keep in mind though that paint will flake off if exposed to direct sunlight and battered by rain and wind. Stain is a bit more durable as it sinks partially into the wood, but eventually, it too will wear off. So it will require regular maintenance at least every few years.
Need a handy outdoor lumber cheatsheet to decide what lumber to use for your project?
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Pressure Treated (PT)
This lumber generally is pine, spruce or fir that has had a preservative forced into the pores of the wood under extreme pressure. This lumber comes in various appearance grades, ratings for ground exposure and different preservatives. This page has a good overview of the different kinds (US-centric though).
For fence posts or other permanent structures where you need to have lumber buried in the ground, PT wood is the best lumber to use. There are other techniques to use to ensure that even the PT lumber doesn’t start rotting pre-maturely but that is for another article.
However, for ground contact around food you are growing such as for raised beds, planters and even compost bins, I would not recommend PT lumber. PT lumber used to be treated with CCA (chromated copper arsenate), which was discontinued because of health risks of long-term exposure to arsenic. PT lumber now is preserved with either CBA (copper boron azole) and ACQ (alkaline copper quaternary).
There is a lot of debate whether or not these new preservatives are safer around food crops. I am not going to take any chance with my family’s health, so I have decided not to use it. If you do decide to use it for raised beds or planters, at least consider lining the inside with plastic sheeting. It’s a good idea regardless of what wood you use, as it will also keep the wood from rotting where it is in constant contact with wet soil.