I want to build a bench like this that can open on top to storage stuffs inside

enter image description here

enter image description here

Source: http://myoutdoorplans.com/bench/storage-bench-plans/

I will use composite decking boards (extra got left over) to build the outside. BUT how do prevent water from getting inside? I could make the top cover using outdoor plywood and put composite deck on top but that would be too heavy for the top to open up. Is it possible to use paper / flashing thing to put in the inside?



So I guess I am thinking about using this membrane but only all small 2x8 section:

enter image description here

Source: http://www.hometips.com/diy-how-to/create-waterproof-dry-space-under-deck.html

But this is Trex RainEscape which could be expensive. Can I use flashing paper or some membrane for tile or roof instead?

  • Is the decking you want to use for the top a radius edge type or straight cut? Do you have a table saw that could be used to true the sides of these boards? I'm thinking of gluing and clamping them together to form a solid, gapless top. Commented Jul 20, 2016 at 11:45
  • Why not use a heavy sheet of plastic like used for a vapor barrier 6mill or thicker would direct the water to the ends.
    – Ed Beal
    Commented Nov 15, 2017 at 0:20

2 Answers 2


If the top is hinged and is overlapping the sides, you could put 1/4 to 1/2 inch rubber weather stripping on the inside of the cover or on the frame to give yourself a nice water resistant seal.

  • But how do I seal the gap between each boards?
    – HP.
    Commented Jul 19, 2016 at 17:10
  • I edited my question with more details.
    – HP.
    Commented Jul 20, 2016 at 5:20
  • 2
    I'd build the whole thing out of marine plywood, make it seal nice and how I like, the clad the exterior with whatever planking or exterior I prefered for aethstetic. Otherwise, you'd be looking into boat building techniques IMO Commented Aug 19, 2016 at 13:06

For the lid, you'll need to support the decking as frequently as it is supported on the deck itself. If your deck joists run every 12" or 16", you'll need to replicate that or the lid will sag. The photo shows benches that are sixty inches long. You diagram show one support in the middle, leaving a 30" span. At summer temperatures, it will be sagging within a week even with zero use.

  • Framing isn't my concern. I use 16" joist spacing so the lid will follow that pattern. But I want to storage stuffs inside. A bit of moisture is OK but it can't be soaking wet. It should be like a mini shed...
    – HP.
    Commented Jul 19, 2016 at 5:23

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