In this video tip, I show you my favorite way for making a deck foundation. Along the way, we'll pull out some tips on preventing rust, rot, frost heave, and uplift. All in two and a half minutes.
Tip: Use a 12 in. diameter pier
This allows some leeway in aligning posts. This keeps the post centered (more ort less) on the pier.
Tip: Wrap pier in plastic
Black polyethylene plastic—often omitted—is pretty important if you live in a cold climate. Wrap it around the form tube and to prevent something called 'Frost Jacking.' Frost jacking is where frozen soil grips and lifts the concrete form tube, but the plastic makes it too slippery. It's not going to be able to grip that and you're not going to have any chance of seasonal frost movement.
The plastic goes all the way down to the bottom of the tube and it makes the outside slippery.
Tip: Hot-dipped is different from electroplated
The post saddle is a U-shaped piece of metal, it is very important that you choose one that is hot-dipped galvanized. Many are not, some are just plain steel, and they'll rust like crazy. Even the electroplated varieties do not resist rust that well.
Tip: Bolt down the saddle
In the center is a shaft, that sinks into the concrete holds the saddle it in place. The problem is that it doesn't really provide a whole lot of resistance to uplift. If your deck is high and wide, or if you've got a veranda roof over it, wind can cause the deck to rise, so that's why I like to drill holes for some expanding masonry anchors.
Do this after the concrete is cured, and it makes sure that those posts aren't going anywhere. Drop the post in place to mark the spots where the bolts are and to drill little pockets for those nuts and bolts so the post will sit on the saddle.
A couple of hot dipped galvanized carriage bolts through the asddle and post pin everything together. Slip the post in and drill the bolt holes through after it is in place.