I’m currently using a piece of plywood to cover a shallow trough and setting flower pots on it; like a small table top. The weather has taken a toll on this piece of wood so I’d like to replace it. Its 20 X 26inch rectangle though the corners are rounded to a more ‘oval’ shape.
I can certainly cut out another piece of plywood, but I’m looking for options. Is there anything else that I can obtain that is fairly inexpensive? It does need to withstand weather conditions and not bow under the weight of the items I put on it.
Plastic? Metal? do they make 'pressure treated plywood? Plywood coated with some protectant?
I know that Menards has (so, I’m assuming whatever hardware / lawn and garden store you have by you should have) pavers 18" X 18"; I’m pretty sure they have 24"X24: - could you use two of those to cover the hole?
You might consider oriented strand board (OSB). It’s commonly used for roof sheathing, comes in 4X8 sheets, different thicknesses and water resistant, not waterproof but I’ve seen it last for several years outside, untreated. To extend moisture resistance, apply one coat of an oil based sealer and 2 coats of oil based paint to both sides and the edges. Or, if you really want protection, use an epoxy paint. If bowing from weight is a concern, reinforce the bottom side with 1x2’s, 2X4’s, etc.
I think OSB is unlikely to last long when it is in a flat, level orientation. It can last a while when it’s standing vertically or even just with enough of a gradient to shed rain, but flat, it’s going to get a pool of water on it every time it rains and that will just soak in; the board will turn to muesli in a fairly short time.
How long does it need to last, and does it need to be a single piece? You can cut an eight foot pressure treated 2x8 into three pieces to cover the trough and they’ll hold up pretty much anything lighter than a car.
If you can do basic woodworking, you could make something yourself. For example, with a pressure treated 2x4 and a cedar fence plank, you could make a cover that’s like a little deck. Cut the 2x4 into 2 or 3 26" sections and put them across the trough. Screw the planks to the 2x4 sections. It should be plenty strong. The cedar is weather resistant and the pressure treated 2x4’s will be okay on the ground.
For a cheap method I would use plywood and and a good exterior paint. House paint is the cheapest (lots of it free on Craigslist in my area), you might even find the wood free on CL too. It would look nicer than pressure treated too. Another option I used on an outdoor shelf my wife uses for plants are ceramic tiles. I found some 24X30 tiles at a garage sale for $2 each and cut them to fit using my Dremel Saw Max. Another option I have would have at this time is some Trex decking, I have about 500 feet of it. I would give you some if you lived nearby.