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Trying not to use pressure treated wood for garden beds, chemical leeching. Would like to use regular wood(cedar is a bit expensive for me right now).

Looking for a suggestion on what to use to treat(stain and/or seal) wood to a little more life out of it then a season of two?

Found several places online, but they're expensive and have to order and ship the stuff.

I don't mind DIY ideas either.

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    Read that as "steal wood for outdoor gardening use" at first. Pressure treated indeed. – Katie Kilian Apr 30 '16 at 1:58
  • Consider cyprus--many of cedar's qualities, but usually far cheaper. – Jeromy French Apr 30 '16 at 2:49
  • I took a stab on what you mean with your last sentence if I am wrong just change it to what you meant. I think something was off either way. – Matt Apr 30 '16 at 3:13
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    With the same question, I opted to go for plain old softwood; no treatment. A bit of gravel underneath might or might not help with drainage/longevity. I'm old enough to remember that pressure treatment with CCA (copper chromated arsenic) used to be considered "perfectly safe". Now, of course, it has been replaced with another "perfectly safe" product. Ask in 20 years if we still think that it's "perfectly safe". – Aloysius Defenestrate Apr 30 '16 at 14:22
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    Would like to use regular wood(cedar is a bit expensive for me right now). Consider what's a better use of your time and money - building something of inferior wood now that's slightly cheaper than cedar or having to replace it in five years (new material expense plus your time and labor). I'd save a bit longer and go for cedar. – grfrazee May 2 '16 at 14:00
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Looking for a suggestion on what to use to treat(stain and/or seal) wood to a little more life out of it then a season of two?

You don't have to treat almost any wood for it to have a reasonable lifespan outdoors. Exposed to the elements without any treatment at all wood can last for a great many years, not just one or two. I compost my wood shavings and used to compost smaller scraps until I discovered that two years buried in an active compost heap had done nearly nothing to break down finger-sized pieces of wood!

Untreated wood will of course weather to the classic grey/silver appearance we're all familiar with but it won't fall apart easily. So using untreated pine or spruce, even in direct contact with soil, five years in decent shape is perhaps at the low end of expected service life.

In addition to this the thicker the wood is the longer it can withstand the effects of weathering and fungal attack, simply because there's more of it there, so just using beefier material will directly equate with a longer lifespan. Although the savings in buying a cheaper species might then be offset by the cost of the chunkier wood.

DIY preservative
If you want to extend the working life further you can make up various preservative treatments for wood. Many of them use borax as the active ingredient, which is great for those in the US where it's commonly available (not too useful for others living elsewhere in the world where it has become a controlled substance).

The borax can be dissolved in hot water until a fully saturated solution is created — add it spoonful by spoonful until no more will dissolve and some crystals remain on the bottom of the pan. This can be painted directly onto the bare wood with a paintbrush or roller. As the solution is colourless once dried on the wood adding food dye or watercolour paint may help in applying it more evenly over larger areas.

If you want to treat posts that will be driven into the ground they should be stood in the liquid for a couple of days for the end grain to soak in as much of the solution as it will take.

You can also dissolve borax into oil and combine it with varnish to make an actual wood finish with preservative qualities but these additional ingredients obviously add to the cost and this is probably overkill for treating something like the wood for raised beds.

Would like to use regular wood(cedar is a bit expensive for me right now).

"Regular wood" covers quite a bit of ground, as geographic availability and cost of certain species varies greatly — from reading posts from American woodworkers it appears someone in one state will be able to get white oak at approximately the price others typically pay for poplar.

Buying from a sawmill or a dedicated wood supplier will also usually make a substantial difference compared to buying wood at a big-box.

There are actually numerous woods naturally resistant to rot that may be cheaper than cedar where you are, including white oak. If you'd like to investigate this option here's a table from the Forest Products Laboratory showing the relative rot-resistance of woods commonly available in North America:

Decay resistance

Anything from the Very Resistant or Resistant columns could probably be expected to last for a couple decades in this application, except if driven directly into the soil.

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  • Anything from the Very Resistant or Resistant columns could probably be expected to last for a couple decades in this application, except if driven directly into the soil. Osage orange can last a century, even when driven into the ground. There are plenty of instances of it being used for fence posts in the American south where they outlast the homestead they're put in for. It's quite an amazing wood. – grfrazee May 2 '16 at 13:58
  • @grfrazee, thanks for that, good to know. Even some of the woods in the Resistant class can easily last more than 20 years in direct soil contact but local variations play such a big part in this I didn't want to give an unrealistic expectation. – Graphus May 3 '16 at 8:59
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As a result of bad planning I ended up using untreated planed softwood (probably pine) and treating it with fence preserver for slightly raised beds (by soaking) . It lasted about 6 years in contact with soil but didn't have to hold back much pressure. The treatment soaks in better on rough sawn timber, and was a modern wax/resin waterproofing product with very little in it to actually prevent rot.

So basically even if you do it quite wrong you can get a few years out of it.

Having replaced the boards (quite a job) I do suggest going with pressure treated timber - I used gravel board. At least here it doesn't use arsenic any more. I gave it a coat of fence treatment as well.

If you really want to avoid pressure treated timber, it would be a good idea to soak the boards in fence treatment and buy thicker boards than you otherwise would have. But note that most fence treatment products, including all that work for any length of time in contact with the ground contain preservatives of some sort. The products that only seal are designed to shed water quickly and don't seal very well for long. So wet soul against them won't do much good.

Here in the UK, you really to have hunt down anything other than pressure treated generic softwood for outside use, and the cost is enormous.

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    I had to go look up what a gravel board was, so I added a link for the convenience of others. Or, at least, one definition of gravel board. It doesn't quite seem to match up with your use of it, though. – FreeMan May 2 '16 at 15:53
  • @Freeman,the definition is good. Thanks. Outdoor timber of the right dimensions (6x1 or 8x1, minimum 6ft long) is often sold under that name. – Chris H May 2 '16 at 17:03
  • I should add that my raised beds have more supporting the boards than usual - the bottom edge of every board is held in place for the whole length. – Chris H May 2 '16 at 17:21
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If you search around, you can see some cultures historically charred wood to preserve it in contact with soil. The main example probably being the Japanese Shou Sugi Ban method, where they char the board, then scrape away the charcoal (oversimplifying it).

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    If you have a chance to embellish a bit this has the workings of a good answer. – Matt May 2 '16 at 18:26
  • I remember I wanted to add this for an answer on another question but couldn't find anything backing it up. +1 to Matt's comment above. – grfrazee May 2 '16 at 21:24
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Since you were looking for finishing options rather than wood choice recommendations, I suggest linseed oil, Tung oil, another oil or some other branded product. You could also seal the wood with a coat or two of polyurethane, varnish, or lacquer.

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