Should I line my Planter with Plastic Sheeting?

UncleGarageJanuary 27, 2014

I built a large privacy planter in my front yard. I used PT wood and the bottom's are exposed earth. I thought it would be a good idea to line the inside with 6 MIL clear plastic. I covered on the interior walls and left the bottom open earth.

My thinking is that the plastic will prolong the life of the wood by keeping the wet soil away from the wood. However, I am noticing that moisture is building up between the plastic and the wood - it gets sun all day long.

Have I made a mistake?

FYI - I tend to overbuild and over-engineer everything...and I enjoy every second of it.

Here is a link that might be useful:

This post was edited by UncleGarage on Mon, Jan 27, 14 at 18:46

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Oxboy555(Las Vegas)

I've never seen anything like this. How does it work with plants? Do you fill that whole thing up with soil to the top? Half way?

It reminds me of the perimeter kill zone at a penitentiary where the SUVs and dobermans patrol.

    Bookmark   January 27, 2014 at 9:19PM
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calistoga_al ca 15 usda 9

I think lining the inside with plastic is effective to help preserve the wood on your raised bed. With no measurements given it is difficult to comment on the basic construction. Al

    Bookmark   January 28, 2014 at 8:59AM
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nil13(z21 L.A., CA (Mt. Washington))

It is a good idea to help keep moisture in the planter. Those types of raised bed can get very dry very quickly if you live in an arid environment.

I'm seeing a much bigger problem though. It looks like you didn't treat the cut ends of the pressure treated lumber. They'll just rot from the inside out that way.

    Bookmark   January 28, 2014 at 11:17AM
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Oxboy555(Las Vegas)

Is there such thing as a plant/soil friendly sealant/protectant that can be applied to the wood planters and containers Something non toxic that can prolong the life of the wood?

    Bookmark   January 28, 2014 at 1:53PM
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Being that your in Ca. your planter box should last you a few years before the moisture builds up and starts to cause you some problems due to the lack of flowing air.

    Bookmark   January 28, 2014 at 2:08PM
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nil13(z21 L.A., CA (Mt. Washington))

oxboy, it depends on how friendly you want it. The current Copper ones aren't that bad. The safest and most effective non-metal based treatment is probably acetalated.

    Bookmark   January 28, 2014 at 8:52PM
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seysonn(8a WA/HZ 1)

Welll, It is not just the wet/moist soil that you are concerned with. The moisture (from air, rain, condensation) trapped under the plastic is just as much harmful to the wood. I would remove the exposed plastic( use a utility knife).

BTW: The PT wood will have enough preservative against rotting for a long time. I use cedar lumber which also more durable than untreated pine.

    Bookmark   January 29, 2014 at 3:02AM
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Thanks everyone for your replies.

@ NIL13 - thanks for your comment on the exposed, cut PT. There is no soil at that level and I am putting a top cap on the planter so I think I'll be ok.

Here is photo of the planter populated with ficus.

    Bookmark   March 10, 2014 at 4:23PM
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Cap is excellent idea - I had build something similar (as tall as yours, just not so long) few years ago. It worked great, but I didn't put cap on immediately and water was getting into the wood and was sitting on top. If you could slope it few degrees toward outside to drain fast, even better...sorry for 'lecturing', you probably know that already.


This post was edited by rina_ on Mon, Mar 10, 14 at 16:55

    Bookmark   March 10, 2014 at 4:52PM
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greenman28 NorCal 7b/8a

I built some beds for my brother last season, and we lined them the same keep chemicals out of the soil. We do need to add a cap, still.


    Bookmark   March 10, 2014 at 5:31PM
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Josh, yours look like 'better' wood, is it cedar? or?
Maybe because mine were that tall, I found water sitting on top for too long and then running down the rest of the boards. And, forgot to mention, I used 2x4 - so much thicker. I did have some extra stakes/supports just like in uncle's photo, that had exposed cuts.
Cap also made it look very finished, I was also using in front right by the driveway.

    Bookmark   March 10, 2014 at 5:42PM
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greenman28 NorCal 7b/8a

that's just the "red" pressure treated color, made to look like better wood. The wood was 2X12 pressure treated.


    Bookmark   March 10, 2014 at 8:06PM
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hoovb zone 9 sunset 23

Wood generally in southern california is damaged faster by uv rays than by rot because it's so sunny and dry here. you don't usually see a planter of that type made from wood because wood doesn't last all that long, compared to say masonry.

I'd be more concerned about what you planted in there. Those ficus are genetically pre-determined to want to be a 50 foot tree with a root system to match. They are going to want to bust out of there pretty quick, even if you keep them cut back.

    Bookmark   March 11, 2014 at 3:03PM
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If your planter faces south the soil temps may get too high. In the dark ages we coated the wood inside planters exposed to moisture with asphalt. It was both organic and eventually, biodegradable. Plastic tends to encourage condensation between the plastic and the wood unless it's glued directly to the wood.

    Bookmark   March 11, 2014 at 7:32PM
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Did that at the cottage years ago. Took 15+ years for some of the 4x4's to show enough signs of rot to replace sections of them. Used heavy plastic to line. Recently had a 5' concrete retaining wall dug down to footing as water was escaping and eroding the front lawn. They used water proofing membrane that has nubbins on it to stand off of the wall. Am embarking on doing a raised planter and will use the same material. Will allow enough of an airspace hopefully to avoid replacing any wood for years to come. Always something new or something new to learn.

    Bookmark   September 14, 2014 at 9:30PM
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