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Green Doug fir raised beds & plastic lining.

Posted by tobina Zone 8 (My Page) on
Tue, Jun 17, 08 at 11:03

My know-it-all neighbor has done it again. I've purchased green Doug Fir lumber very inexpensively for an adventurous raised bed project. It has been fun to build, but now he informs me it's going to rot in 2 years.

I purposefully chose not to use cedar because the price of cedar in the PNW was about 10x that of green timber! I fully expect the beds to rot a good deal over time, but I am hoping for at LEAST 5 years before they do so!

Does anyone have any last second ideas to increase the life span on these things and help prove my neighbor wrong? I am still in the construction phase so everything goes.

I have thought about buying some sort of heavy duty plastic (pond-liner stuff?) with which to line the entire interior of the beds, essentially removing the dirt-on-wood contact altogether.

I live quite literally on the former grounds of an old dairy barn and everytime I dig down 2 feet I find old concrete footings about 4" thick and a foot wide, I've thought of using these as footings so the corner posts of the beds sit on concrete, not dirt, and then covering the base of the beds with sawdust or barkdust or whatever I use to line the garden paths in the garden.

What do you all think? Any other brilliant ideas out there? ...or am I doomed to rotted wood in 2 years despite it all? =/ Hope not! =)

Tobin


Follow-Up Postings:

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RE: Green Doug fir raised beds & plastic lining.

Covering it with something to reduce contact with wet soil will help a bit. How important is the appearance of the wood to you? Are the beds functional, as with vegetable beds, or are you trying to create a decorative bed that has to look good for a while?

The reason I ask is that if you don't mind that the wood starts to look a bit funky in a couple of years, as long as it continues to support your raised soil for planting, it will function as planned. You could plant something that spills over the sides if you want to hide the wood, or plant something in front of the beds that will tolerate the shallow soil, like perennials.

An alternative is treated wood, less expensive than cedar and will hold up longer than fir.


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RE: Green Doug fir raised beds & plastic lining.

Though the beds are about 20" high and do have a bit of design to them, the appearance is certainly not 1st and foremost to me. I borrowed the idea from a book and copied it directly. I'm no carpenter, but they weren't that difficult to build. I am making 8 of these beds...the cost was major issue...with cedar the price would have been ~$1300...with green wood it was only $250!

Anyhow, I actually LIKE the look of weathered, gray wood...I guess it reminds me of the coast. I am certainly not going for the look of a deck or something polished with these beds. I probably should have done PT lumber, but the green was so cheap and I dislike those little indents on PT and the fake orange color they have. All that probably would have faded anyway.

Ah well, again if it can last at least 5 yrs I'll probably be ready for another project anyway! Maybe cedar will have come down a little by then...the guy at the lumber store told me some big mills have just closed in B.C. and that was contributing to cedar's big increase in price relative to green.

Hiding the wood with trailing plants is a great idea that I am up for, too. Perhaps after 3yrs I could grow a bunch of Boston Ivy up around them as well?


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RE: Green Doug fir raised beds & plastic lining.

How thick is the wood? I think that will be a very relevant consideration. I used untreated fir 2x8s for a 'temporary' raised bed that was in place for 5-6 years before it got replaced. At the end of that time, the boards had definitely started to rot but were still providing solid support and probably would have for another few years. 1x4s or 1x6s would have not stood up well, based on the amount of rot that was happening on the 2x8s.


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RE: Green Doug fir raised beds & plastic lining.

I am using 2x8s as well! 5-6yrs, perfect...that is all I expect to get out of them in the first place. I do think I will line the inside of the beds with plastic as that is quite cheap these days. Thank's all for your input!

Do you guys think it is worthwhile to line the bottom of the bed with something to prevent moles from coming in or is this overkill? I'm thinking overkill as the price of 1/2" metal mesh in 4' x 100' rolls is more than ALL of the wood I bought.


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