Step Three of Building a Deck

Pouring your piers and installing your posts is really the first time you will see your deck come together. You will be able to imagine what it will look like and give you motivation to continue. The posts that support your deck can be set above or below ground level. Setting your posts above ground in post anchors can reduce the potential for damage from moisture, another benefit is that it makes it easier to repair or replace a damaged post if the situation presents itself. Setting posts below ground is an alternative that requires fewer tools and materials, but calls for longer posts. If you are confident that little to no moisture damage will occur than I would go with the below ground option. It is a lot easier and produces the same results. Yes, you may have to spend a few extra dollars on longer posts but it will be worth the extra hours of labor it takes to put them above ground. Precast concrete piers with metal post anchors already in place are another option. Set the piers on concrete footings that extend 6 inches below the frost line. This is more difficult than any option, it may seem easier at first but getting the level and line set is hard and usually frustrating.

First I will explain how to set posts above ground. First place a fiber tube form in each hole and nail two 2x4's to it on opposite sides. You can get these fiber tubes at any lumber yard or home improvement store. Level the form so it sits 3 to 4 inches above the ground and about 8 inches from the bottom of the posthole. Mix up a bag of concrete in a wheelbarrow or flat surface and fill the forms to the top with concrete and work it with a 2x4 to remove air pockets. I also like to use a piece of skinny metal as it is easier to push in and out of the concrete. Level the concrete by dragging a 2x4 across the form. The concrete needs to be level because you will be installing a post base on top of the form. There are two options for the next step but I highly recommend one over the other. You can either push a J-bolt into the wet concrete to hold the post base. Leave 1 inch of the threaded end sticking out. Center the J-bolt with a plumb bob hanging from the intersecting mason's lines used to lay out the posts. Or you can use a post base that is made to sit in concrete. Just go to your local hardware store or home improvement warehouse and get a post base for concrete applications. All you do is set the whole base in the wet concrete and you are done. For those doing it the hard way, read on. Allow the concrete to set for at leas 48 hours then remove the 2x4's. Cut away the fiber tubing and backfill with soil and rocks and tamp to make it solid. Place a post base on the J-bolt and bolt it in place, tightening with a ratchet and socket wrench. If you are using the J-bolt method be sure to get adjustable post bases so you have some play where to stick the bolt through. If you get a pre-made concrete anchor you can skip the last step. Finally, cut a post so that when it is placed in the anchor it is at least a few inches higher than the bottom of the ledger. Place the post in the anchor and nail it. You'll cut the post to final height later.

Next I will explain how to set your posts below ground, which I prefer. First you need to retie the layout mason's lines, then shift them 1-3/4 inches toward the deck's outside edges. This will mark the outside edges of the posts automatically. Cut posts so that when put in the holes their tops are at least a few inches above the bottom of the ledger. Seal the bottom of each post with roofing cement or some kind of end sealer. With a helper holding the post in place, nail a 1x4 brace to it. Next, plumb the post with level, then drive a 2x2 stake into the ground and attach the brace to the stake. Making sure the post is plumb again place another brace on its adjacent face. Again mix up a bag of concrete and shovel it into the hole around the post. Work a skinny piece of metal or a 2x4 in and out of the hole to release air bubbles. Add enough concrete to fill the hole and then check again to make sure the post is plumb. You have time once the beam is in the concrete to make adjustments so don't be shy to move it as much as needed. Next shape the concrete around the base so it slopes away from the post to improve runoff. Let the concrete set for at least 48 hours before removing the braces.

Continue the steps for every post until they are all set. Once they are in, you are basically looking at the shape of your deck, if you have some imagination. If you see any abnormalities in the posts after 48 hours you need to investigate them right away. Even though you may have to replace one now, it is much better than having to do it when the whole deck is complete. Trust me, I've gotten impatient before and left a bad post in, it does awful things to a finished deck. Take the time to make sure it is right the first time. Now you are ready for the beams, and I will explain how to do that in my next article.