Pergola designer
Size
Size the pergola.
12 by 12 ft, 9'-0" under the beam
The beams run along the width and the rafters along the depth. 2 posts per beam, 2-ply 2x12 beams, 2x6 rafters. Height is measured to the underside of the beam: the braces need at least 6'-8" clear at their foot.
Attachment
Stand it alone, or hang it from the house.
Freestanding, on its own posts
Freestanding: four or more posts and knee braces both ways, so it stands without the house.
Posts
Posts and footings.
6x6 posts, 4 in all, on bases
4 footings, 26 in round pads, 42 in down. Braces 24 in legs, foot at 7'-0".
Beams
Beams and lumber.
2-ply 2x12, double beam
OK, 81% used (bending, snow case)
Rafters
Rafters.
2x6 at 16 in
OK, 77% used (bending, snow case). 12 rafters, 14'-0" long.
Slats
Slats across the rafters.
2x2 slats every 8 in
OK, 6% used (bending, snow case). 22 slats, 14'-6" long. Closer slats give more shade and a heavier roof.
Overhangs
How far the roof reaches past the posts.
Beams 12 in, rafters 12 in, slats 3 in
Overhangs stay at or under a quarter of the span behind them. Longer ones are flagged for your review.
Loads
Snow, wind and the ground.
30 psf snow, 115 mph wind
The snow load and wind speed start at 30 psf and 115 mph. Enter the values your building department gives. Wind 115 mph, snow 25.2 psf on the roof, 349 lb uplift per post.
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