Hi all,
I’m building a pergola over a deck. The pergola will be supported by 7″ diameter old porch columns which are 7′ high. The columns have a narrow open core and are turned from solid stock. I’m concerned about securing them top and bottom, and also about how to attach railings to them. How is this typically done?
Thanks,
John
Madison, Wisconsin
Getting the details right for a wall assembly with the control layers to the exterior and lots of drying potential.
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Replies
I don't know if this is "typical" and it will depend on other details but I cut a piece of 2xPT to fit in the column and attach that to the deck. You can do the same on the top if the column doesn't have a capital. I cut the ends of my railings on a radius to fit the columns and attach directly to the column. The rail profile will determine whether you can just angle large screws, use a bracket, slot out for a rail bolt or maybe let in the rail. Here is a pic of a simple bandsaw pivot jig for curving the railing ends. It's probably self explanatory, base piece of plywood, pivot on the inside and in line with the front edge of the blade, moving fence that centers the rail with the pivot. Don't cut through the fence.
Hammer1: Thanks for your reply and ideas. I think they'll work. For attaching the railings, I think the radius on the rail, along with screws and glue, ought to keep them in place. And the 2x plugs should hold the columns in place. I didn't know if there were any trade secrets about doing this correctly.
Thanks again.
Same way here, except that I like to have something to bear loads vertically when someone sits on the railing. Just relying on screws there could let the wood split out above screw and railing settle down. So I use an angle of metal under the joint screwed into both rail and column, or I put a block of wood sized to the elevation of the bottom rail ( <4" ) under it.Also, the reason the inside is hollowed out is to let it breathe and not rot. This space must vent top and bottom, so an open dado is needed, and cap tjhe top off with lead or copper so water stays out.
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It seems there's a lot involved to installing the columns correctly so they're secure and will weather the elements. Is there a Fine Homebuilding article on the subject?
When I installed my columns, I cut equilateral triangles to align the top and bottom and prevent lateral movement. They were all lot easier to cut than circles, and were easy to 'tweak' to fit perfectly within the columns. Once I had these attached, I lifted the roof, slid the column over the bottom triangle, aligned the top, and gently released the jacks. This method gives no uplift protection so use with caution depending on your situation.
Anothe advantage to this method is that it allows for ventilation through the column (as Piffin mentions).
Fyi, each side of the triangle should be the square root of 3 times the radius (inside) of the column.