How to Frame a Modern Pergola
If you are trying to figure out the best way to give your outdoor space a contemporary edge, this tutorial will walk you through how to frame a pergola.
Building your own pergola might feel like a daunting task, and the truth is, it’s not fast or easy. But it is doable and can add value to your home.
How to Frame a Pergola: Step by Step
The pergola we’re building includes 6×6 posts and a wall mount frame. The goal is to have the pergola frame circle from one end of the wall mount frame, around both posts, and back to the other end of the wall mount. To do this, all frame components must be level.
Step 1: Finish Your Boards
Start by finishing your redwood boards (e.g., staining, painting, and/or sealing) and allowing them to dry. Doing so will make your life much easier since this method allows for working on the ground.
Step 2: Measure from the Wall Mount to the Corner of the Post
Measure from the wall-mounted frame cutout to the outside corner of your post. Mark this distance.
Step 3: Use a Miter Saw to Make Your First Cut
The end next to the wall mount will be flat (90 degrees), but the end of the board that joins your post will be a 45-degree mitered corner.
Adjust your miter saw to 45 degrees, then cut your lumber. Position the wood so that your cut extends outward from your measured distance. In other words, your measured distance should be the shorter side of the mitered corner cut.
Step 4: Predrill for Lag Bolts
Predrill for your 3-1/2” lag bolts. First,dry-fit the mitered board on your wall-mounted frame and pergola post. Then, mark the best place for lag bolts so that they don’t hit other bolts, the wall-mounted frame boards, or the gap in between the boards.
Step 5: Ratchet the Lag Bolts in Place
Have a helper or two hold the board in place while you ratchet in the lag bolts with washers. (Don’t forget the washers!)
No matter what part of the pergola frame you’re installing, always check for level before and during installation. This includes installing lag bolts at any point. Don’t trust your eyes. Use a level.
Predrill for lag bolts, then ratchet in the lag bolts (plus washers) onto your pergola post near the mitered corner.
Tip: Install one bolt completely, ensuring a level frame board, before you do the others. Doing so holds the board in place more accurately than a helper can.
If you’re building a pergola, deck, or anything involving multiple lag bolts, we recommend the purchase of a socket set for your impact driver or drill. At just $40 for a large set, this tool will speed up the process of ratcheting lag bolts. Plus, it saves your arm strength.
Put the ratchet bit onto your power tool, and let the impact driver do the work. It’s so fast. (We’re sad we wasted half our morning with a hand-ratcheting tool. This is definitely the way to go when building a pergola frame.)
Step 6: Repeat on the Opposite Side
After you install the first board, do the opposite board of your frame. Measure each distance individually to ensure square and level posts.
Hopefully, your measurements are identical, but if they’re not, it’s better to cut one frame board a bit longer or shorter to fit a straight post than to force a leaning pergola.
Step 7: Cut and Install Your “Floating” Board
The final component of your outer pergola frame is the floating board opposite the wall mount. It will have two mitered corners. Measure from post corner to post corner, and use this measurement to mark the positions of the shorter sides of your 45-degree mitered cuts.
Always predrill for lag bolts, use washers, and tighten in opposition.
With this third board of your pergola frame install, you need to check each lag bolt position to avoid colliding with bolts already installed into the 6×6 pergola posts.
If you’re satisfied with this outer frame for your pergola, you can move on to installing the pergola slats.
Step 8: Add a Second Layer for Stability (Optional)
We decided that, for added stability and proportional aesthetics, we wanted to add a second 2×6 layer to each side of the pergola frame. The wall mount frame already has two redwood 2x6s, so it makes sense that the rest of the frame would match.
To do this, measure the inside of the existing pergola frame, corner to corner.
Cut your pre-stained 2×6 redwood lumber to that length, then measure and mark the center. Mark 1-1/2” out from each side of the center – this is where your double beam will go.
Tip: It’s easier, when possible, to measure and mark lumber when it’s down on the ground rather than up in the air.
Start at the center and measure outward the distance you want your lag screws to hold the outer frame boards together.
Because the wall-mounted pergola frame lag screws are spaced 32” apart, we kept this same distance for the lag screws on the three other frame boards. Use a template to mark your two lag screw positions in relation to the sides of the board. (Example shows about 1” in from top and bottom sides.)
(Full disclosure: Except flanking center, where we distanced the lag screws 8” out from either side of the center so there would be greater support near the point where the center beam would fall. So, there’s a 16” space between the center two lag screw positions, and 32” spaces out from there. Do your math, so that your end lag screws end up between 2”-6” from the lumber’s ends.)
Predrill all lag screw holes.
Lift, then clamp your second frame board into place. Clamp top to bottom and face-to-face.
With the second frame board clamped in place, predrill through your already-drilled holes into the existing frame board. Do this for all lag screw holes.
Insert your 2-1/2” lag screws (don’t forget the washers) into the holes, and ratchet them in.
When the first lag screw of the set is in, you can remove the face-to-face clamp for more room if needed. Otherwise, keep the clamps in place.
Here’s what your doubled-up pergola frame will look like. It’s stronger, sturdier, and looks better. That’s a pergola design trifecta if ever there was one.
Repeat this process for the other two pergola frame sides. One of the sides doesn’t need the center beam considerations because the beam will only be running one way (perpendicular to the direction of your pergola slats) and, therefore, only connecting to two of the four pergola frames sides.
A solid doubled-up pergola frame perimeter looks much more balanced than having a single 2×6 pergola frame on three of the sides.
It will be much more secure, too, for bearing the weight of the pergola slats.
If you find your pergola frame boards don’t align as well as you’d like (redwood, like all wood, doesn’t come perfectly straight on every board), here is a simple trick to force the wood to align:
Take two short scraps of 2×4 or 2×6 and hold them against the top and bottom of your lumber pieces that need aligning. Clamp these boards into place, and the lumber will align. Adding the boards broadens the face of the clamps and provides more leveling force. Even with this method, though, you’ll need to clamp the boards face-to-face as well.
The inside corners of your pergola frame will look like this, with the two secondary frame boards abutting the pergola posts.
Here’s a good illustration of proportion. You can decide for yourself if you think the second 2×6 is worth it. For us, it is absolutely worth it.
Step 9: Add the Center Beam
Now that the pergola frame perimeter is installed, it’s time to tackle the center beam.
Measure the distance between your two center marks on the interior pergola frame boards. Cut two pre-stained 2×6 boards to this length, and lay them on top of each other.
Screw these two boards together to create one beam before mounting them to the pergola frame.
You might notice that, again, parts of the two boards don’t align. For example, the ends of these boards were about 1” off from each other.
To remedy this, take two scrap pieces of wood and set them on the ends that need aligning. Clamp into place.
You can see here that the ends are now perfectly aligned and ready to be screwed together. Wood is very forgiving that way – it can often be bent or torqued to meet your needs, as long as you know how to do it.
With your center beam boards clamped together, determine your pergola slat spacing. You’ll be screwing the beam boards together and don’t want screws where your slats will go. Lay out scrap wood to get an idea of your preferred spacing.
This example will use 10” slat spacing, center to center.
Starting at the center point, measure 10” out toward the ends. Do your math to determine if you want the slats to flank center (in which case you’d mark 5” out from the center point in each direction) or if you want a center slat. You’ll want the end slats to fall roughly the same distance from the pergola frame boards as the rest of your slat spaces.
When your slat positions are marked, predrill two screw holes into every other space between the slat marks.
Install exterior wood screws into your predrilled holes.
Then flip the beam over and predrill two screw holes into every other space on that side. These should leapfrog the screws on the other side so that each space has just two screws, either from side A or side B of the beam (as opposed to having four screws in one space and zero screws in the next space).
Take out your HD Kreg jig and drill two pocket holes onto each end of your beam. Be sure to clamp the jig into place and hold it securely while drilling (not shown).
Tip: Place two holes closer to the center on one side of the beam…
…and place the two holes closer to the board sides on the other side of the beam. This will help keep the pocket screw tips from running into each other.
Have helpers hold the beam squarely in place, based upon your 1-1/2” out-from-center markings you made in the beginning. Install your HD pocket screws, two per side (so, four per end) of the beam. Then repeat for the other end of the beam on the other pergola frame perimeter board.
And, just like that (haha), you’re done! Your pergola frame is installed and ready for the pergola slats.
We love the uniformity of the lag screw placement all the way around the interior of the pergola frame. These will be painted matte black in the near future, but for now, it helps to see where they are. Even the shortened screw spacing flanking the center beam looks consistent.
We will also be touching up the pocket holes with stain to help protect and preserve the wood. Our opinion is that it’s much easier to do stain touchups with the boards installed than it is to stain the entire boards after installation.