We finally finished and mounted the trellises. They were made from the cheapest one-by construction lumber we could find. We planted bougainvillea vines to grow on them. Eventually most of the trellises will be hidden behind the bougainvillea vines. The diamond shapes were designed to complement the windows on the nearby garage door. We looked at a design with a horizontal bar instead of the middle diamond, but Spouse prefers the three diamond pattern.
Details and Lessons Learned
* We used four 1x6 (8 foot) boards which cost $4 each from our local plywood store. That's fifty cents a board-foot.
* To achieve consistency in the lap joints, we cut dados across the boards, then ripped them apart into the narrow strips.
* I tend to think of the saw when I want to make dados. It wasn't easy to crosscut dados in the ends of 8 foot boards on a jobsite table saw. I messed up a couple boards before I decided to use a router with a clamped straight board to guide it. That worked much better (duh!). Old habits die hard.
* The diamond ends are rabbeted so that the diamonds are partially inset in their squares.
* I made a jig to cut the rabbets in the points of the diamonds. The jig holds each diamond so that the left point extends at a "right angle" over the dado blade, to cut the rabbet behind the point. The right side of the jig is guided by the table saw fence. You need four passes per diamond. The jig is nothin' fancy.
* The trellises (and jig) were glued with Titebond III.
* The trellises were primed, then painted with exterior latex paint. Painting went poorly. Spouse tried painting with a brush and got a lot of runs, so we tried sprayers with poor results, then quit while we were behind. See this thread for our experiences with sprayers:
* The long screws were hidden inside 3 inch standoffs made from white sprinkler pipe.
* I cut the sprinkler pipe using a stop block on the miter saw. I used my hand to hold the sprinkler pipe against the fence during the cuts. I had safety concerns related to hand holding the round sprinkler pipe. After a careful test cut, it was clear that I did not need a "pipe holder" jig and proceeded with the repeated cuts.
* I learned that plastic sprinkler pipe sawdust is messy to clean up, made worse by the static cling.
* We mounted the trellises with 4-3/4 inch SPAX T-Star Plus #14x flat head construction screws. If we number the horizontal rails 1-9, then the six mount points are behind the outside lap joints at the ends of rails 2, 5, and 8.
* I predrilled the screw holes with a 3/16 inch brad point drill, according to the instructions on the screw package. My #10 countersink was not sufficient, so I used a larger twist drill (3/8 inch?) to make the countersinks. The twist drill caused a lot of tearout in the soft wood, so after we mounted the trellises, we cut off the splinters with a chisel, covered the problems with wood filler, and then sanded and repainted those areas. (Remember, the trellises will be covered with plants.)
Big Box Store: Three horrible, ready-made trellises would have cost $75 at the big box store.
Me: $16 for construction lumber boards (plus minuscule amounts of glue, paint, etc.). That does not include the two boards I messed up on the table saw, which were used on other projects.
Me, oh yeah: Add $20 for an awful paint gun that I may someday use again, but probably not. It was a nice try, but we didn't need it.
Big Box Store: Long and short sticks, nail-gunned in a cross-hatch pattern. A child might recognize the overall shape as "rectangle!", but maybe not.
Me: Three trellises, custom-designed to match the house. Handcrafted, lap-jointed, sized to fit.
Big Box Store: Zero fun.
Me: Sometimes fun, sometimes not. :-)
Big Box Store: $0 labor.
Me: Probably $1000s worth of labor. It was a labor of love.
I freely acknowledge that this was way too much time and effort, compared with what was needed. I over-engineered these trellises because they will be permanently mounted to the house, because I wanted to test and practice certain woodworking skills, and because of a certain pride in workmanship. They aren't perfect, but they are way more than they needed to be, and I know that, so please don't beat me up too much about the extra work involved. I get it. At least I didn't bother to put a finish on the rabbet jig. :-)
* Trellises, mounted on wall.
* One of the windows on the roll-up garage door, showing the diamond pattern.
* Jig to cut rabbets behind the points of the diamond shapes, to partially inset the diamond shapes in their square spaces. See the description above.