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DIY modern slat pergola

After struggling with our lawn for the past couple of months, we committed to mulching over it entirely. It’s practical, low maintenance, and great for our dogs but also a little bit ugly. Our entire yard is brown with no hope of it turning green, so we had to think of another way to bring in some vegetation.

The modern slat pergola is still a lot of brown, but the goal is for the star jasmine to climb up and create a lush backdrop for our outdoor space!

Supplies

  • (60) 1×2 cedar boards

  • (2) 2×8 cedar boards

  • (4) 2×4 cedar boards

  • fasteners

  • Stain – I recommend Ready Seal

Supplies

  • kreg jig

  • nail gun

  • table saw

  • miter saw

Squaring up the pergola to the house

The first thing I wanted to do was to make sure that the pergola would be square with the side of the house. I did this by attaching a jig to the corner of the open patio and using a level gauge to ensure that each axis was orthogonal to one another and to the reference plane. This is important so that the pergola wouldn’t be wonky looking down the yard. Our fence follows the property line and is, at least in theory, parallel to the side of our house.

I rested an 8-foot slat on top of the fence and attached it temporarily to the jig, making sure that it was level. Then I used a handy bit of trigonometry to determine orthogonality with the side of the house: a 3-4-5 right triangle. Measuring and marking 4 feet down my 8-foot slat, and 3 feet down my jig I moved the slat so that the hypotenuse measured exactly 5 feet. Voilà! This slat is now perpendicular to the plane of the house, and probably perpendicular to the plane of the fence. I left the jig in place since it was not in the way, and started building the supporting structure of the pergola on top of the fence.

Building the supporting structure

For our project and tool set it made sense to buy 2×8 cedar boards and then rip them to 2×4 nominal dimension on the table saw. It also gave use the opportunity to use two different tones of cedar, as the 2×8 boards are made from the center of the tree (darker red) and the other boards are made from the outer rings of the tree (lighter). I also ripped the o.g. 2×4 boards to 2×2 to span between the verticals. I cut the verticals to length so that when the 2×2 boards were stacked on top it the 1×2 slats lined up where I wanted them to, with a slight pitch away from the house (1 or 2 degrees).

I added some “feet” to the bottom of each vertical with some wood glue and finish nails, as well as a 45-degree cut on two of the 2×2 boards that would go on either end. This was a purely aesthetic choice. I then fastened the verticals to the top board of the existing fence at a spacing of 4’6” on-center (o.c.) with two 2.5”exterior-rated kreg screws into the pocket holes I drilled on either side of the vertical board.

Once all of the verticals and spanning boards were securely in place, I added two more 2×2 boards to span the gap between the fence and the house on either end of the structure, which ended up being approximately 8 feet. This also got rid of a bit of “lean” I had on the first vertical I placed (due to the warp in the existing top board of the fence), and got the pergola back to square.

Spacing and fastening the slats

I initially wanted to space 20 slats about 10 inches apart, but quickly realized that this was too big of a gap and looked weird – so we doubled the number of slats. I had about 19 feet to cover, and dividing it up by 40 or so slats gave me 4-3/8” spacing between. I made a spacing jig out of some scrap cedar so that spacing the slats could be done quickly. For the house side I made a separate jig so that the slats would have the right slope away from the house. Doing this over again, I would have added a ledger board first so that I would have had support on either end of each slat as I went, but the crude jig and pocket-hole method worked out alright. I ended up adding a wood hanger board under all of the slats on the house side of the pergola as an after-thought.

Using another 1×2 to span the middle of the pergola and fastening it to each slat ensured that the various warping in the slats evened out and pretty much aligned with one another. The last steps were to add additional vertical slats down the fence line (simply finish nailed in place), apply a coat of Ready Seal in Natural Cedar to all of the surfaces, and then hang up string lights. Hopefully our Star Jasmine grows quickly this summer!

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