I'm looking for advice for an inexpensive, temporary covering for underneath our picnic table. We do not have a deck or patio and our picnic table has been on grass over the past few years. Eventually we would like some kind of porch/deck but cannot afford to do that right now.
Go to a gardening shop and buy some flat rocks and build yourself a small deck to set your picnic table on. Or if you know of any wooded area, see if you can find some large flat rocks for free. Just make sure that you're not trepassing on someone's property.
Any large fallen trees in your area? If you use a chainsaw to cut the trunk into equal width circles you can lay them down as a paving surface. Prepare your ground area but digging down enough to make the trunk circle lay flat and level with the ground.
I got some old pallets (some places will give away their broken ones), put some cheap plywood sheets on them, painted them and planted lilies around the edges to hide the edges. I made mine big enough to put up a screen room on. I use the big eye screws to anchor it with. Made a 12x16 "patio" for about $200. I did buy some of the pallets new so that added to the cost but would have cost lots more to build a deck or have a concrete slab poured. And it was quick.
You can purchase a piece imitation grass that is made to install on concrete patios.
Home Centers sell it by the yard ... it comes in various widths. Very reasonable priced and you can hose it down too.
You can also purchase a small piece to cover top of picnic table for a different table decoration!
I recently bought a few "rubber" mats, each about 4' x 6' and maybe 1" thick, at Tractor Supply to put under my picnic table and Little Tyke's cottage so I could quit dragging them around the yard when it came time to mow. They work great! Each cost around $35, well worth the price to save the work and time I used to waste weekly. The kids love the solid floor of the cottage, too.
I just use any old piece of low nap carpet indoor carpet lasts for years outside. There is always someone with used carpet to get rid of for the hauling or call carpet installers.
Post a "wanted" ad for pavers on Freecycle or Craigslist. I got all the bricks I needed to build a bread/pizza oven for free that way.
I don't know much about how things need to be treated for outdoors, but my initial thought was to take two or four sheets of plywood, put them together somehow, and paint them -- one color, or a different color for each sheet, or some sort of design, or maybe a family effort even involving the little kids -- and then treat them with something that would be weather-resistant. I'm beginning to think the wood would just rot, though. But I like the visual I get when I think about it.
I know someone who put down an indoor-outdoor rug (not one of those patio rugs) about 10 x 14 and it has been there for years. It's starting to get a little rough around the edges, but it does work.
You can buy temporary patio squares that love together for any surface