Attaching posts to a cement patio can seem like a baffling job. There’s simply no way to attach them directly because wood won’t join to cement. You need something that will join the two of them together. Even then you won’t have a perfect, strong fit. If the posts are being used for a deck, for instance, at the corners they’ll need to attach to a strong upper framework to keep the structure secure.
Step 1 - Brackets
You need to start by laying out where the posts will meet the cement patio and mark the center of each spot. Having done that, it’s time to buy the brackets and anchors. You will be able to find the U brackets in hardware stores. They’re made of stainless steel, so they won’t rust, and the sides form a square around the post. The will be a bottom to be bracket so it effectively acts as a cap.
In the center of the bottom will be a hole. This is for the anchor that attaches there and goes into the concrete. You need to select anchors that are at least 4 inches long. This will give sufficient depth to offer proper support to the posts on the cement patio.
Step 2 - Drilling
For drilling to the cement, attach a concrete bit to the drill. You need a bit that is no wider than the anchor. If it’s too wide the anchor won't grip tightly enough in the cement and your posts will wobble.
The best way to know you’ve drilled far enough is by marking the bit at the required depth. A small piece of masking tape will do the job well. Ensure that the bit goes down vertically into the concrete, not at an angle. After you’ve drilled each hole you need to remove the cement from it. If possible, use compressed air for this as it will leave a clean, straight hole.
Step 3 - Anchors
Slide the anchor through the hole in the U bracket and push it into the hole. It should go all the way down, with the base of the bracket resting on the cement. You can achieve a firmer bond by putting a later of silicone caulk on the bottom of the bracket (for a firmer hold, use epoxy, but give it ample time to dry before proceeding).
Step 4 - Posts
With the bracket in place, you’re now ready to secure the posts into the brackets. Slide each post into the bracket until it’s pushing against the metal bottom. There will be a hole, possibly two, on each of the side panels. You need to hammer a nail through each of these holes so that each side of the post is secured to the bracket. This will keep it firm. If you’ve used epoxy to keep the brackets in place on the cement you should now have a firm bond for each of the posts against the cement patio.