Options for Curved Pergola Rafters


Old 04-24-15, 12:18 AM
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Options for Curved Pergola Rafters

I'm planning approximately a 40' x 16' pergola build from PT lumber for my home. My rafters would be 2" x 6" x 16'. I've considered using a curved design for the rafters (such as the example photo below). In researching what it would take to bend wood it seems steaming or using laminate are the options. I don't have a setup for steaming wood of that length and building the laminate dimensions seems to be an extraneous effort for my pergola size. Not to mention I'm unsure how the laminate and adhesives would hold up to the weather.

I've read where some lumber yards may produce curved wood, but perhaps it is only certain wood species? I planned to stain the wood anyway so if I mix wood species (ie: cedar and PT) in my build would it be noticeable?

I can certainly call the lumber yards in my area to see what options are available for curved lumber, but I'm kind of at a lost on how else to achieve my design.

Any advice is appreciated. Thanks.

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Old 04-24-15, 05:16 AM
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Curved Beam | Perfect Accent for Vaulted Ceilings, Archways

Glulam - APA €“ The Engineered Wood Association

There are two sites that may have curved wood to order. Don't try to bend it yourself.

I knew a guy who's company had 4 full sized flat bed trailers filled with made to order curved steel headers parked near an airport. It was for a new building. On memorial day weekend, all 4 flat beds were stolen. I said that the CIA took it. The Blue Angels were in town & their C130 could have easily flown it to Central America, over night. Everyone laughed at me & said that it wasn't them, it was the mafia who took it & sold it for scrap.
Old 04-24-15, 05:21 AM
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You can certainly forget about steaming.

Doing a large radius is certainly better than small for the laminating concept but you really are not doing this on your own with off the shelf lumber. If you are layering pieces face to face as in a stack of cards, you would have a very time consuming job to create the number of arches you need

To do the bends and laminating you would have to surface the material on a jointer and plane it to a bendable thickness. The material would also have to be fairly clear lumber as knots will change the stress points within the wood and make for inconsistent layering of the pieces. You would have to have a large enough (flat) work surface to create the pattern you would need to laminate the pieces together on. You then need a lot of clamps and assistance to keep ahead of the process of applying the adhesive and adding the strips while getting the clamps in place. I cannot overemphasize the amount of work you are in for if you want a decent looking project.

The alternative is to use the largest lumber you can to develop the appropriate radius and segment the arches with overlapping joints with the lumber in the standing on edge position. This might be 2 or 3 thicknesses of 1" to 1-1/2" lumber. After the material is laminated with fasteners and either an appropriate glue or adhesive you will have to mark and cut the top and bottom curves with a saw capable of handling the job and then do some final dressing of the cuts to look acceptable.

In the millwork end of my business I have done several projects involving laminating and radius work. Some have been interior trim work and some have been for things like curved porch railings and even curved window sash. The shop though, has large enough equipment to handle the job.

I think your plan of finding a company that builds these is a better approach if you really want to have the curves.
Old 04-24-15, 10:15 PM
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Why not make the curved members out of weathering-steel tubing? A good man with a torch can make beautiful curves.
Old 04-25-15, 06:08 AM
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Not the the wood would be easy, but wouldn't steel beams be a bit heavy to lift without equipment?
Old 04-25-15, 09:56 AM
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A 5 x 3 x 3/16 rectangular steel tube weighs 9.42 lb. per foot, meaning the OP's 16-footers will weigh about 151 lb. each--not too difficult for one person to erect using a few step ladders, and a breeze for two people. I lifted a 22-footer of the same size into place by myself a few years ago on a carport I built, so I know it can be done (even by someone approaching geezerhood).
Old 04-25-15, 10:10 AM
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Laminate two pieces out of 2x12 stock in two our three sections, then cut to your desired curve.

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