Build your own Curved Rafter Cedar Pergola. Plans available for download in PDF Format.
See the How to Video.
For this blog post I’d like to go back and revisit a curved pergola I built with my friend Doug a few years ago.
Build the Pergola
The Sketchup Model
The pergola is made from rough sawn Western Red Cedar and sits on the lid of an underground 2800 gallon concrete cistern. The homeowners collect rainwater in the cistern for use on their gardens in the summer months.
The six posts are spaced 8′ apart across the front, and about 6’6″ on the sides.
The overall height of the curved pergola is 9’5″ with a head clearance of 7’3″.
The posts are 6×6 and, in this particular installation, simply are held in place by weight and galvanized alignment rods that are set in shallow holes in the concrete lid and up into the bottom of each post.
Alternatively the posts could be attached to concrete footings with galvanized saddles.
Two 6×6 beams are bolted to the posts and run North to South.
Fourteen curved rafters are attached to a 6×6 beam and a 2 by 9-1/2″ ridge beam.
Along the sides of the pergola are 8 curved corner braces.
There are 6 slightly larger curved braces that stiffen the structure side to side and add support to the rafters.
Topping the structure are three 2×4 louvers.
The number and spacing of the louvers can be changed to increase the shade under the pergola.
The posts, and all other parts, are full dimension.
The posts are 6″ x 6″ and cut to length with a circular saw.
For this video I have enough lumber around from other projects to show the steps to make each part of the curved pergola
I draw a pencil line around the post with a speed square. If the post is square and true then the lines will meet.
I make 4 cuts with a circular saw. Rotating the post a quarter turn each time. Then finish the cut with a hand saw.
They are then chamfered using a power plane. A sanding disc on an angle grinder will work for this as well.
A hole is drilled in the center of the bottom of each post for the galvanized rod.
This rod will keep the post in position. I use a drill guide for this to ensure the hole is square to the end of the post.
If you want to see how to lay out the post locations for pouring concrete footings have a look at my previous pergola video.
A shingle is added between the concrete and post as a moisture barrier.
Stakes are driven in and temporary braces are added as we set each post in place, then plumbed with a spirit level.
The layout and size of this pergola was determined by the size and dimensions of the concrete cistern lid.
The lid was found to be square and level so this made everything easier.
6×6 beams sit on the posts.
On each end they have a 30 degree bevel to form a point. Like the posts, I mark a line around each beam with a square.
I set my circular saw at 30 degrees and make four cuts.
The plans include a cut list for the saw mill. Every part of this build was cut at Doug’s workshop ahead of assembly so we were pretty fussy with tolerances and lumber selection from the mill.
This could also be done with a large miter saw.
If the beam is square then you are left with a nice point. I cleaned up the handsaw cuts with a chisel.
These beams sit down on the posts an inch. I cut this dado with a series of close saw cuts across the beam.
Then break off the pieces with a mallet. And finish up the groove with a chisel.
Each 6×6 beam has three of these dados. One for each post.
The beam is flipped over and a counterbore and hole drilled for the lag bolt that will secure the beam to the top of each post.
The ridge beam is 2″ x 9.5″. 30 degree angle cuts are made on each end of this beam. When complete, the beams are also chamfered with a power plane.
The beams are lifted onto the posts and the lag bolts run in with a socket wrench.
A temporary bridge is set in place across the beams to hold the ridge beam in place at the proper height.
The rafter locations are marked on the underside of the ridge beam and galvanized strapping is screwed on. This strapping will make setting the rafters easier and will also add strength to the roof of the pergola and prevent sagging.
The Curved RAFTERS
I start by making a pattern for the curved shape of the rafters.
The pattern will be cut from thin plywood. I lay out a grid with tape measure, pencil, and straight edge.
Then I mark points where the curve intersects the grid.
I tap in a nail at these points then bend a thin strip of metal across them to form the upper and lower curve of the rafter.
I used a strip of linoleum edge metal for this.
I trace the curve on the plywood with a sharpie.
On the plans I also show the radius values for the two curves that make up the shape of the rafter. The curves could also be struck with a long straight piece of trim like a compass.
Over sawhorses I rough off a piece of the pattern to make the next step easier.
Then cut the upper profile of the pattern with a jigsaw. Then use a belt sander to smooth and shape.
I reposition the pattern to cut the other curve.
The location of the beam is also marked on the pattern then this birds mouth is cut.
We had our sawyer mill boards just over 12″ wide for these rafters. Alternatively, thinner boards could be glued up to get the width required but, it’s a lot easier to just have them cut to what you need.
The pattern is traced on the rafter blank.
We cut the 12 degree angle in the upper and lower ends of the rafter with a circular saw.
We cut the curved sections of all our rafters on a large bandsaw.
But, if working alone a jigsaw cuts almost as well. I use a heavy, stiff blade on my jigsaw for this 2″ thick Western Red cedar.
My friend Doug is a very artistic and skilled carpenter. We worked on quite a few design ideas for the curved rafters. We wanted the most elegant curve with the minimal waste of material. We decided on the idea of pairs of rafters that were supported with a ridge beam. And that each rafter tapered down from the center top to the sides. This was done by using two different radius curves. The homeowners approved the design and we all thought it looked a bit like an upside down wooden boat hull.
Each rafter was then chamfered with a sanding attachment on an angle grinder.
These rafters were set in place and toe screwed to the beams. And also screwed to the galvanized strapping attached to the ridge beam.
Then the temporary supports for the ridge beam can be removed. Or left there until all the braces are added.
A pattern is also cut for the two brace shapes. Again I use 1/4″ plywood for the two patterns.
The curves will be scored with nails through a yardstick-size piece of plywood with a pivot laid out on my workbench.
I mark the pivot and two curve radii then drill pilot holes. Then tap in finishing nails.
On the small brace pattern I mark the two 45 degree angles first. Then I nail the blank to the workbench.
Along a pencil line on the bench I tap in the pivot point nail then sweep the yardstick along the blank to scratch the curve on the plywood. Then draw a pencil line along this scratch. I darkened it with a sharpie as well.
The 45 degree angles were cut on the miter saw.
The second, slightly larger brace pattern was made in the same way.
The plywood blank is bigger and the radii that I need to scratch in the wood is also greater.
As before I make a compass for striking the arcs from a thin strip of plywood, measure and drill pilot holes, and tap in some finishing nails.
I mark the points for the 45 degree cuts then secure the blank and the compass pivot to the bench. Then scratch the arcs on the wood. Then darken the curves and take the blank to the miter saw.
I use a bandsaw to cut the brace pattern curves. A jigsaw would also work just fine.
Then I sand these curves smooth on a small belt sander.
Both patterns only took a few minutes to finish. This little sander is so handy, I use it a lot.
The pattern was copied to the cedar brace blank referencing one straight edge on the board.
The 45 degree edge of the speed square is used to align the pattern before tracing. This is repeated for the second larger brace. To save material I nest the braces into each other on the board. Alternating them if possible depending on any rough sections or large knots in the red cedar.
And just like the patterns, the braces are cut on the miter saw then the bandsaw.
This could also be done with a speed square, circular saw, then jigsaw.
Cedar Curved Pergola Outdoor Structure
After sanding the curves smooth on a hobby belt sander I bevel the edges with a sanding disc on my angle grinder.
The last step in prepping the braces is to drill holes for the lag bolts.
I mark a point half way along the flat section of the brace where it mates to a post, beam, or rafter. I draw a line 90 degrees to that point, then another 20 degrees off that.
This way the lag bolts will pull the brace into the corner.
Now I copy this mark to the brace. Then mark the center of that location.
I tilt the table of my drill press to 20 degrees.
And clamps some stops to the table to help hold the brace. With a forstner bit in the chuck I counterbore a hole on each end of the brace.
Swap the bit, then drill through for the shank of the lag bolt and washer.
These larger braces had one additional cut that was done on site. The brace was laid in place against the rafter and scribed. This piece was then removed so the brace would fit tightly to the shape of the rafter.
To attach the small braces I hold them in place and drill into a post then beam. Then with an impact driver I run in the galvanized lag bolt. This is a clip from my woodshed build where I used a similar curved brace.
Eight of these braces are required for the sides of the pergola and attach to the posts and 6×6 beams.
This process was repeated for the larger braces that are secured to the posts and rafters.
Now all the temporary bracing is removed.
The three louvers, or more if needed, are made from 2×4 stock. They are simply cut to length then chamfered. They are positioned over the rafters and screwed in place.
And that is it. The curved pergola is done. Let me know what you think by dropping a note in the comment section. I try to reply to as many questions as I can.
Thank you so much for reading.
And thanks to everyone who has supported our channel through Patreon. It’s very much appreciated.
I have a full set of plans available for download.
If you have any questions, please leave them in the comments below. Thanks for reading
See also: Shed Style Garden Pavilion
Pictures after 5 Years
Here’s some pictures taken last November to show how the pergola has aged. I think it’s holding up very well. It’s the worse time of year for any flattering photos but maybe that’s okay.
There’s a long crack in one beam but that’s all I could find of any significance.
And that’s all. Thanks!
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- Dewalt 12″ Sliding Compound Miter Saw (DWS779)
- Dewalt Miter-Saw Workstation Tool Mounting Brackets (DW7231)
- Dewalt Heavy Duty Miter Saw Stand (DWX723)
- 10″ Bench Drill Press with Laser
- Dewalt 20V MAX Compact Drill/Driver set
- Dewalt 20V Battery Charger
- 20V Dewalt Batteries
- Milwaukee 7 1/4″ 15 Amp Circular Saw (6390)
- Bosch 1375A 4-1/2-Inch Angle Grinder similar to mine
- 4-1/2-Inch Sander Backing Pad with Lock Nut
- Electric Hand Planer
- Excellent Hammer
- Woodworking Chisel Set
- Pipe Clamps
- Irwin Tool Quick-Grip Clamp Set
- Laser Level
- 48″ Spirit Level
- Johnson 7″ Speed Square
- Adjustable Combination Square
- Framing Square
- Swanson 12″ Speed Square
- Carpenter’s Pencil
- Orange Mason Line
Adhesive & Finish
Drill Bits & Blades
- Grizzly Master Forstner Bit, 31-Piece (H7694)
- Countersink Drill Set
- Brad Point Drill Bit Set
- Long Drill Bits
- Drill Guide
- Bosch 9″ Jigsaw Blades
- Bosch 6″ Jigsaw Blades
- Oscillating Tool Blade Pack