Last Saturday, my husband and I built 5 boxes for raised beds in the back yard. I’m SO excited to finally get my edible garden started, and this construction project was one of the first steps. This was also the first time that I have had to purchase lumber to build a raised bed. Keep reading for more info on why we decided to build boxes and what you should know about choosing and buying wood for your own raised beds.
Why Garden in Raised Beds
When you build raised beds, you bring in soils and amendments to fill the beds. This means gardening isn’t dependant on what native soil you have. In urban spaces, the native soils have almost always been stripped away, compacted, or contaminated, and you are left with less-than desirable vegetable growing zones. In my yard, it’s compacted, mixed with gravel, and all around crappy.
Of course, you can always amend native soils with manures, composts and cover crops, but that takes time, and in some cases, like yards filled with fill-dirt or solid adobe, it’s not feasible.
Raised beds can be made from anything. I have made beds from salvaged materials, including urbanite at my last house, rocks, and from log rounds left from a tree removal. Technically, you don’t even need to use materials to hold up the soil, you can just make a mound on the ground. However, I prefer to form boxes or established edges, not only to keep my soil in one place but to make it just a bit harder for my dog to go running through and destroy everything.
When it comes to wood, I’ve been lucky. My job as recycling coordinator allowed me access to scavenge the municipal dump pile for reclaimed boards that I used to build my first apartment garden. My second garden in Santa Rosa used the mill ends from my dad’s small-scale mill, giving me 4×15 beds that were at least 18″ tall at no cost. However, this time, with no access to a free pile and my dad is no longer milling, I purchased lumber.
How to Choose and Buy the Right Wood for Raised Beds
Choose redwood for raised beds. DO NOT use pressure treated or railroad ties.
Redwood trees are able to live so long because they are naturally rot and insect resistant. Things built from the wood from these trees have the same properties. That’s why you see houses built in the 1800’s and early 1900’s, built with redwood, with no insect damage and are still standing just fine (my 1900 Victorian included).
Redwood is expensive because the trees grow slowly and are less common, so nowadays, things are built with fir or pine that has been pressure treated. These are woods with no natural resistance but are less expensive. They are treated with chemicals to prevent them from rotting and or having bug damage. Those same chemicals that prevent rot or bug chews can leech into the soil. I don’t know about you, but I know I don’t want those things in the soil. Even though arsenic is no longer used in most treated wood, I’m still not comfortable having my food near anything pressure treated. If you want to know more about the chemicals of pressure treated wood, check out this document.
Shop at a Local, Independent Lumber Yard
You can get redwood lumber at the big box stores, but your options will be more limited. A local lumber yard will have many more sizes and finishes to choose from. Plus, the quality is usually better. The big orange store, for example, only sells boards by the piece, which means you have to use what they have, which may not be large enough and you have to put two together, or, it’s too long.
An independent lumber yard will sell by the board foot (usually cut to even 8’, 10’, 12’, etc., but it’s fair to ask if they will do odd lengths), meaning you can buy only what you need and have less waste.
Choose the Correct Redwood Grade
Redwood comes in different grades, the most common are known as ‘Con Common’ and ‘Con Heart’. The ‘Con’ is short for “Construction”. Con Common wood is much less expensive than Con Heart, but will have a mix of white and heart wood, plus some knots. The white wood, or the sap wood, from the tree is much less insect and resistant than the darker, heart wood. I think this is fine for raised beds, but if you can afford it, go with heart wood. However, this type of wood does run about 3x more per linear foot.
There is also a grade of Clear Heart, which is all heart wood and no knots. This is the most expensive, and while beautiful, a bit overkill for an outdoor raised bed.
Choose a Finish that Works for You
You have the option of smooth or rough. Rough boards are sold how they come off the sawblade. They are flat and square, but you could not easily run your hand down it without getting splinters. Smooth boards have been run through a planer or sanded down, removing all the splintery and fuzzy bits.
“S4S” is how lumberyards will denote “surfaced 4 sides”, meaning this board has been smoothed down on all four sides. Sometimes you can find S2S, which would be just two sides.
Both smooth and rough are perfectly fine for raised beds, but a personal choice. Check with your lumber yard on if there is a cost difference. Surprisingly, smooth was less expensive in my area, which is what I went with.
Lumber isn’t Full Dimension. Choose the Right Size Wood.
You want your bed to be built from at least 2″ thick boards. This is the standard size for decking wood, as opposed to fence boards (which are puny 1″). Any larger in width is known as a timber, and a whole economic class up.
However, a 2″ decking board won’t actually be 2″. Wood is no longer cut ‘full dimension’, so the wood is actually smaller than the measurements. The length is always true (actually, always measure what you buy, it’s possibly longer and you might have to trim off a bit), but the width and thickness are smaller. These are known as ‘nominal’ sizes. A 2×6 board, for is 1.5″ x 5.5″. A 2×8 board would be 1.5″ x 7.5″.
Just like lengths, you can buy in different widths. The lumber yard I shopped at had 2×6, 2×8, and 2×12. I wanted my beds to be about 16-18″ tall. That meant I stacked 2×6 boards 3 rows high, to give me 16.5″ tall beds. Choose what works for you. Most veggies need at least 12″ of good soil to grow in. Deeper is always better, but remember, that means more money spent on the soil to fill.
Do Some Math and Puzzle Work Before You Shop
Lenght totally depends on your space, but I suggest building beds that at either 3 or 4 feet wide. My last house had 4′ wide beds, and those were a bit hard for me to reach over, so this time, we went with 3′. I have 3 different lengths, 2 beds that are 10′ long, 2 that are 8′, and one that is 12′.
Consider the sizes of beds you are building, and piece together how you can get it from the least amount of wood. For example, I needed 3’ sections for my ends. Instead of buying 8’ sections, cutting out two 3’ sections and losing the extra 2’, I bought 12’ and got 3 sections with no waste.
To build my 5 beds, I bought (16) 2x6x12, (12) 2x6x10, and (9) 2x6x8. I had only one 3′ section of waste, which I’ll use for my next set of beds (that I hope to build in the spring). I also got (4) 4x4x8 to use as the posts in the corners, which I cut into 16.5″ sections.
I can’t wait to show you my raised beds all filled with soil and planted with my fall veggies!