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I’m building a storage bench for a community garden. My goal is to build it to last for 10 years with minimal maintenance. It is essentially a big wooden chest that is 24” x 20” x 72”.

I plan to use 2x6 boards with alternating butt joints for the exterior similar to the picture below and then 3/4” plywood on the interior.

I’ll use 3” deck screws, pressure treated pine wood, and set the bench on pavers.

QUESTION: Are there any other recommendations to improve the durability of this storage chest?

enter image description here

RWL01
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    Seems that what you've got in mind should last well beyond the 10-year requirement. The plywood might be problematic. It could trap water between itself and the other boards. – gnicko Jun 15 '23 at 19:56

2 Answers2

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I think you have it pretty much covered using pressure-treated and deck screws, which are obviously intended for exterior use.

The wood
Decent pressure-treated softwood won't win any beauty contests after 10 years with zero maintenance (although it should still be holding together just fine given the total potential lifespan is four times this) but with a little care every now and then it should still look very good, and the construction should still be rock solid.

Very much optional, but one extra step to consider doing if any of the board ends will be in contact with the pavers or facing the sky is to seal the end grain with epoxy1.

The screws
Buy a good brand or type with good user reviews and/or independent testing results as deck screws are very much not all equal.

Given the thickness of the material, that this is softwood and that the screws will bite into end grain I would recommend that you go with 4" screws for a bump in holding power.

The plywood
The plywood is a concern if water will get to it, so I'd suggest either waterproofing it thoroughly2, or buying proper marine plywood (rather than just relying on exterior-grade ply, which is of questionable consistency these days).

1 This is very simple and quick to do. Make a tape 'dam' around the board end first, burnish the tape down well. Mix your epoxy and pour or slather it on the end until it's completely covered; if the first application soaks away you might add a little more, but that's not strictly necessary. Peeling the tape off should present no difficulty because paradoxically epoxy doesn't bond well to the sticky side of masking tape. I'd use 30-min epoxy so you don't have to rush, but this can be done with 10-min or even 5-min epoxies if that's what is available and/or affordable.

2 One good option here being 'bed liner' which is 100% waterproof, flexible and very resistant to heavy stuff being dropped on to it :-)

Graphus
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Keeping everything dry will be key. Setting it off the ground on pavers is a good start. If possible, try to locate it somewhere sunny. There should be drain holes in the bottom (or leave gaps between the boards when you're building the bottom, just like if you were building a deck).

You didn't say how you're building the top, but it should be something that keeps the rain out.

Mike Baranczak
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