Precisely Placed Posts
A simple right triangle ensures accurate placement of deck posts.
I frequently work with groups of volunteers on Habitat for Humanity projects that require footings to support deck posts. To ensure the accurate placement of these holes, I created a large 3:4:5 right triangle made of three pieces of 1×2 poplar. The 5-ft. section that makes up the hypotenuse intersects the other two boards at 3 ft. and 4 ft. I made the 3-ft. section (the part that rests against the house) a little longer to create a stronger joint. I ran the 4-ft. section (the part that’s used to locate the holes) out 7 ft. to create a longer reach. Where the pieces meet, I created half-lap joints with a router and then drilled holes to accommodate a short bolt and wing nut to secure them.
At grade level on the foundation, we mark where the centers of the posts for the deck need to be. We then measure the distance where they need to be from the house along the long leg of the triangle and mark the ground with paint or stakes. For holes that will be installed farther out, we either run a string or a longer board parallel to the 7-ft. section and measure along that. When finished, I remove the wing-nut connectors and wrap the three pieces together to stow in my van. To make this device easier to reassemble, I color-coded where the pieces join. Recently I loaned it to the professional masons our Habitat affiliate hired to dig and place concrete form tubes for post footings. They were reluctant to give it back at the end of the day.
—Andrew Dunn, via email
Edited and illustrated by Charles Miller.
From Fine Homebuilding #320
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