Pergola: I wants one

[AZRedhawk44]

I've got a 5 x 10 experimental garden in my backyard.  It does well when I plant it in February, up until about May when no matter how much water I give it, the AZ sun scorches everything into deadly submission.

I wants a pergola over the top of it, and I want to expand the size of my garden to about 15 x 15.



This one above is for a nice relaxing patio, and is slatted to allow some sun to get through while still regulating it and creating some shade.

I was thinking that I would build pergola with legs out to 10' x 10', and crossbeams that stretch out 2.5' on either side, centered inside a 15 x 15 garden.  There would be 2.5' of garden surrounding the edges of the pergola.  The shade generated would move through the garden as the sun moves its arc through the sky, and I'd have less burning of my vegetables.  I'd also use the pergola as a support structure to mount solar panels on top of, which would further reduce the amount of sun that gets through.  The solar panels would provide DC power for a sprinkler timer and irrigation valve, and also power my workshop.

And if I need to further reduce the amount of sun, I can use suncloth or some other screening fabric and temporarily string it between the crossbeams during the summertime.

I am looking for advice on how to go about fastening the legs of the pergola to the ground.  I was thinking I would build concrete platforms for each of the legs (about 1 cubic foot for each footing), and use pieces of rebar anchored deeply into the ground and through the wet concrete to secure it against strong winds.  Then a piece of stamped metal 4x4 concrete footing to hold each pergola leg to the concrete.

Will that be enough weight and resistance to keep the pergola legs anchored to the ground, even during our monsoon wind storms we get in AZ in July each year?  We can get 60mph winds pretty routinely then.  I would prefer not to sink wooden posts directly into the ground, because they will eventually rot.

[rcnixon]

I'd go a couple to three feet deep into the ground and a foot or so above.  Set threaded rods in the top to bolt the steel brackets as used on deck legs.  Six by six pressure-treated legs should do it unless you use more than a post at each corner.  Two by eights as a ring joist around the top and vertical two by sixes set close enough to provide the kind of shade you want.  Over-building is my middle name.

Don't forget to leave an open area in the middle of the garden for sitting and enjoying.  Look into raised-bed gardening, you can get all the way around the beds for cultivation without actually stepping into them.  You can hang mist nozzles from the overhead to help control the temperature and humidity during the really hot and dry days.  How about winter plantings?  Are you far enough sout to avoid hard freezes?

Russ

[Hawkmoon]

The Simpson Strongtie company makes post anchors for this purpose. They work for both lateral location and to resist uplift.

[AJ Dual]

If it's the shade you're after, and there aren't secondary aesthetic concerns that also make you need the pergola style, there are various kinds of mesh tarps one can hang to provide partial shade, but with enough sun to grow plants still, you see them at garden centers and nurseries.

Maybe Giga can recommend something.

Seems like it would be a lot less effort, and possibly cover more sqft more cheaply.

[French G.]

I'd dig a hole and set 6"x6" min in quikcrete. Pressure treated ought to make it at least 20years in the concrete, probably much more. For something more replaceable I have considered the same posthole and concrete but set with a piece or CRES or galvanized steel that a wood post would fit in. Would have to be handy at the top with bolts and wedges to firm and square the posts.